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• Scale filter crashes with error when used from transcoding example

  27 juin 2017, par Vali

  I’ve modified a bit (just to compile in c++) this code example :
  https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/transcoding.c.

  What works : as is (null filter), a number of other filters like framerate, drawtext, ...

  What doesn’t work : scale filter when scaling down.

  I use the following syntax for scale ( I’ve tried many others also, same effect) :
  "scale=w=iw/2 :-1"

  The error is : "Input picture width (240) is greater than stride (128)" where the values for width and stride depend on the input.

  Misc environment info : windows, VS 2017, input example : rtsp ://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mov

  Any clue as to what I’m doing wrong ?

  Thanks !

  ---

  EDITED to add working code sample

  ---

  #pragma comment(lib, "avcodec.lib")
  
  #pragma comment(lib, "avutil.lib")
  
  #pragma comment(lib, "avformat.lib")
  
  #pragma comment(lib, "avfilter.lib")
  
  
  
  /*
  
  * Copyright (c) 2010 Nicolas George
  
  * Copyright (c) 2011 Stefano Sabatini
  
  * Copyright (c) 2014 Andrey Utkin
  
  *
  
  **** EDITED 2017 for testing (see original here: https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/transcoding.c)
  
  *
  
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  
  * of this software and associated documentation files (the "Software"), to deal
  
  * in the Software without restriction, including without limitation the rights
  
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  
  * copies of the Software, and to permit persons to whom the Software is
  
  * furnished to do so, subject to the following conditions:
  
  *
  
  * The above copyright notice and this permission notice shall be included in
  
  * all copies or substantial portions of the Software.
  
  *
  
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  
  * THE SOFTWARE.
  
  */
  
  
  
  /**
  
  * @file
  
  * API example for demuxing, decoding, filtering, encoding and muxing
  
  * @example transcoding.c
  
  */
  
  
  
  extern "C"
  
  {
  
      #include <libavcodec></libavcodec>avcodec.h>
  
      #include <libavformat></libavformat>avformat.h>
  
      #include <libavfilter></libavfilter>avfiltergraph.h>
  
      #include <libavfilter></libavfilter>buffersink.h>
  
      #include <libavfilter></libavfilter>buffersrc.h>
  
      #include <libavutil></libavutil>opt.h>
  
      #include <libavutil></libavutil>pixdesc.h>
  
  }
  
  
  
  
  
  static AVFormatContext *ifmt_ctx;
  
  static AVFormatContext *ofmt_ctx;
  
  typedef struct FilteringContext {
  
      AVFilterContext *buffersink_ctx;
  
      AVFilterContext *buffersrc_ctx;
  
      AVFilterGraph *filter_graph;
  
  } FilteringContext;
  
  static FilteringContext *filter_ctx;
  
  
  
  typedef struct StreamContext {
  
      AVCodecContext *dec_ctx;
  
      AVCodecContext *enc_ctx;
  
  } StreamContext;
  
  static StreamContext *stream_ctx;
  
  
  
  static int open_input_file(const char *filename, int&amp; videoStreamIndex)
  
  {
  
      int ret;
  
      unsigned int i;
  
  
  
      ifmt_ctx = NULL;
  
      if ((ret = avformat_open_input(&amp;ifmt_ctx, filename, NULL, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
  
          return ret;
  
      }
  
  
  
      if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
  
          return ret;
  
      }
  
  
  
      // Just need video
  
      videoStreamIndex = -1;
  
      for (unsigned int i = 0; i &lt; ifmt_ctx->nb_streams; i++)
  
      {
  
          if (ifmt_ctx->streams[i]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)
  
              continue;
  
          videoStreamIndex = i;
  
          break;
  
      }
  
      if (videoStreamIndex &lt; 0)
  
      {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find video stream\n");
  
          return videoStreamIndex;
  
      }
  
  
  
  
  
      stream_ctx = (StreamContext*)av_mallocz_array(ifmt_ctx->nb_streams, sizeof(*stream_ctx));
  
      if (!stream_ctx)
  
          return AVERROR(ENOMEM);
  
  
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
  
  
          // Just need video
  
          if (i != videoStreamIndex)
  
              continue;
  
  
  
  
  
          AVStream *stream = ifmt_ctx->streams[i];
  
          AVCodec *dec = avcodec_find_decoder(stream->codecpar->codec_id);
  
          AVCodecContext *codec_ctx;
  
          if (!dec) {
  
              av_log(NULL, AV_LOG_ERROR, "Failed to find decoder for stream #%u\n", i);
  
              return AVERROR_DECODER_NOT_FOUND;
  
          }
  
          codec_ctx = avcodec_alloc_context3(dec);
  
          if (!codec_ctx) {
  
              av_log(NULL, AV_LOG_ERROR, "Failed to allocate the decoder context for stream #%u\n", i);
  
              return AVERROR(ENOMEM);
  
          }
  
          ret = avcodec_parameters_to_context(codec_ctx, stream->codecpar);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Failed to copy decoder parameters to input decoder context "
  
                  "for stream #%u\n", i);
  
              return ret;
  
          }
  
          /* Reencode video &amp; audio and remux subtitles etc. */
  
          if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
  
              || codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
  
              if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO)
  
                  codec_ctx->framerate = av_guess_frame_rate(ifmt_ctx, stream, NULL);
  
              /* Open decoder */
  
              ret = avcodec_open2(codec_ctx, dec, NULL);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);
  
                  return ret;
  
              }
  
          }
  
          stream_ctx[i].dec_ctx = codec_ctx;
  
      }
  
  
  
      av_dump_format(ifmt_ctx, 0, filename, 0);
  
      return 0;
  
  }
  
  
  
  static int open_output_file(const char *filename, const int videoStreamIndex)
  
  {
  
      AVStream *out_stream;
  
      AVStream *in_stream;
  
      AVCodecContext *dec_ctx, *enc_ctx;
  
      AVCodec *encoder;
  
      int ret;
  
      unsigned int i;
  
  
  
      ofmt_ctx = NULL;
  
      avformat_alloc_output_context2(&amp;ofmt_ctx, NULL, NULL, filename);
  
      if (!ofmt_ctx) {
  
          av_log(NULL, AV_LOG_ERROR, "Could not create output context\n");
  
          return AVERROR_UNKNOWN;
  
      }
  
  
  
  
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          // Just need video
  
          if (i != videoStreamIndex)
  
              continue;
  
  
  
          out_stream = avformat_new_stream(ofmt_ctx, NULL);
  
          if (!out_stream) {
  
              av_log(NULL, AV_LOG_ERROR, "Failed allocating output stream\n");
  
              return AVERROR_UNKNOWN;
  
          }
  
  
  
          in_stream = ifmt_ctx->streams[i];
  
          dec_ctx = stream_ctx[i].dec_ctx;
  
  
  
          if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
  
              /* in this example, we choose transcoding to same codec */
  
              encoder = avcodec_find_encoder(dec_ctx->codec_id);
  
              if (!encoder) {
  
                  av_log(NULL, AV_LOG_FATAL, "Necessary encoder not found\n");
  
                  return AVERROR_INVALIDDATA;
  
              }
  
              enc_ctx = avcodec_alloc_context3(encoder);
  
              if (!enc_ctx) {
  
                  av_log(NULL, AV_LOG_FATAL, "Failed to allocate the encoder context\n");
  
                  return AVERROR(ENOMEM);
  
              }
  
  
  
              /* In this example, we transcode to same properties (picture size,
  
              * sample rate etc.). These properties can be changed for output
  
              * streams easily using filters */
  
              enc_ctx->height = dec_ctx->height;
  
              enc_ctx->width = dec_ctx->width;
  
              enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
  
              /* take first format from list of supported formats */
  
              if (encoder->pix_fmts)
  
                  enc_ctx->pix_fmt = encoder->pix_fmts[0];
  
              else
  
                  enc_ctx->pix_fmt = dec_ctx->pix_fmt;
  
  
  
              /* video time_base can be set to whatever is handy and supported by encoder */
  
              //enc_ctx->time_base = av_inv_q(dec_ctx->framerate);
  
              enc_ctx->time_base = dec_ctx->time_base;
  
  
  
  
  
              /* Third parameter can be used to pass settings to encoder */
  
              ret = avcodec_open2(enc_ctx, encoder, NULL);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);
  
                  return ret;
  
              }
  
              ret = avcodec_parameters_from_context(out_stream->codecpar, enc_ctx);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Failed to copy encoder parameters to output stream #%u\n", i);
  
                  return ret;
  
              }
  
              if (ofmt_ctx->oformat->flags &amp; AVFMT_GLOBALHEADER)
  
                  enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
  
  
              out_stream->time_base = enc_ctx->time_base;
  
              stream_ctx[i].enc_ctx = enc_ctx;
  
          }
  
          else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) {
  
              av_log(NULL, AV_LOG_FATAL, "Elementary stream #%d is of unknown type, cannot proceed\n", i);
  
              return AVERROR_INVALIDDATA;
  
          }
  
          else {
  
              /* if this stream must be remuxed */
  
              ret = avcodec_parameters_copy(out_stream->codecpar, in_stream->codecpar);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Copying parameters for stream #%u failed\n", i);
  
                  return ret;
  
              }
  
              out_stream->time_base = in_stream->time_base;
  
          }
  
  
  
      }
  
      av_dump_format(ofmt_ctx, 0, filename, 1);
  
  
  
      if (!(ofmt_ctx->oformat->flags &amp; AVFMT_NOFILE)) {
  
          ret = avio_open(&amp;ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Could not open output file '%s'", filename);
  
              return ret;
  
          }
  
      }
  
  
  
      /* init muxer, write output file header */
  
      ret = avformat_write_header(ofmt_ctx, NULL);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Error occurred when opening output file\n");
  
          return ret;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  static int init_filter(FilteringContext* fctx, AVCodecContext *dec_ctx,
  
      AVCodecContext *enc_ctx, const char *filter_spec)
  
  {
  
      char args[512];
  
      int ret = 0;
  
      AVFilter *buffersrc = NULL;
  
      AVFilter *buffersink = NULL;
  
      AVFilterContext *buffersrc_ctx = NULL;
  
      AVFilterContext *buffersink_ctx = NULL;
  
      AVFilterInOut *outputs = avfilter_inout_alloc();
  
      AVFilterInOut *inputs = avfilter_inout_alloc();
  
      AVFilterGraph *filter_graph = avfilter_graph_alloc();
  
  
  
      if (!outputs || !inputs || !filter_graph) {
  
          ret = AVERROR(ENOMEM);
  
          goto end;
  
      }
  
  
  
      if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
  
          buffersrc = avfilter_get_by_name("buffer");
  
          buffersink = avfilter_get_by_name("buffersink");
  
          if (!buffersrc || !buffersink) {
  
              av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
  
              ret = AVERROR_UNKNOWN;
  
              goto end;
  
          }
  
  
  
          snprintf(args, sizeof(args),
  
              "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
  
              dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
  
              dec_ctx->time_base.num, dec_ctx->time_base.den,
  
              dec_ctx->sample_aspect_ratio.num,
  
              dec_ctx->sample_aspect_ratio.den);
  
  
  
          ret = avfilter_graph_create_filter(&amp;buffersrc_ctx, buffersrc, "in",
  
              args, NULL, filter_graph);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
  
              goto end;
  
          }
  
  
  
          ret = avfilter_graph_create_filter(&amp;buffersink_ctx, buffersink, "out",
  
              NULL, NULL, filter_graph);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
  
              goto end;
  
          }
  
  
  
          ret = av_opt_set_bin(buffersink_ctx, "pix_fmts",
  
              (uint8_t*)&amp;enc_ctx->pix_fmt, sizeof(enc_ctx->pix_fmt),
  
              AV_OPT_SEARCH_CHILDREN);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
  
              goto end;
  
          }
  
      }
  
      else {
  
          ret = AVERROR_UNKNOWN;
  
          goto end;
  
      }
  
  
  
      /* Endpoints for the filter graph. */
  
      outputs->name = av_strdup("in");
  
      outputs->filter_ctx = buffersrc_ctx;
  
      outputs->pad_idx = 0;
  
      outputs->next = NULL;
  
  
  
      inputs->name = av_strdup("out");
  
      inputs->filter_ctx = buffersink_ctx;
  
      inputs->pad_idx = 0;
  
      inputs->next = NULL;
  
  
  
      if (!outputs->name || !inputs->name) {
  
          ret = AVERROR(ENOMEM);
  
          goto end;
  
      }
  
  
  
      if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_spec,
  
          &amp;inputs, &amp;outputs, NULL)) &lt; 0)
  
          goto end;
  
  
  
      if ((ret = avfilter_graph_config(filter_graph, NULL)) &lt; 0)
  
          goto end;
  
  
  
      /* Fill FilteringContext */
  
      fctx->buffersrc_ctx = buffersrc_ctx;
  
      fctx->buffersink_ctx = buffersink_ctx;
  
      fctx->filter_graph = filter_graph;
  
  
  
  end:
  
      avfilter_inout_free(&amp;inputs);
  
      avfilter_inout_free(&amp;outputs);
  
  
  
      return ret;
  
  }
  
  
  
  static int init_filters(const int videoStreamIndex)
  
  {
  
      const char *filter_spec;
  
      unsigned int i;
  
      int ret;
  
      filter_ctx = (FilteringContext*)av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));
  
      if (!filter_ctx)
  
          return AVERROR(ENOMEM);
  
  
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
  
  
          // Just video
  
          if (i != videoStreamIndex)
  
              continue;
  
  
  
          filter_ctx[i].buffersrc_ctx = NULL;
  
          filter_ctx[i].buffersink_ctx = NULL;
  
          filter_ctx[i].filter_graph = NULL;
  
          if (!(ifmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO
  
              || ifmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO))
  
              continue;
  
  
  
          filter_spec = "null"; /* passthrough (dummy) filter for video */
  
          //filter_spec = "scale=w=iw/2:-1";
  
          // filter_spec = "drawtext=fontfile=FreeSerif.ttf: text='%{localtime}': x=w-text_w: y=0: fontsize=24: fontcolor=yellow@1.0: box=1: boxcolor=red@1.0";
  
          // filter_spec = "drawtext=fontfile=FreeSerif.ttf :text='test': x=w-text_w: y=text_h: fontsize=24: fontcolor=yellow@1.0: box=1: boxcolor=red@1.0";
  
  
  
          ret = init_filter(&amp;filter_ctx[i], stream_ctx[i].dec_ctx,
  
              stream_ctx[i].enc_ctx, filter_spec);
  
          if (ret)
  
              return ret;
  
      }
  
      return 0;
  
  }
  
  
  
  static int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index, int *got_frame, const int videoStreamIndex) {
  
  
  
      // Just video
  
      if (stream_index != videoStreamIndex)
  
          return 0;
  
  
  
      int ret;
  
      int got_frame_local;
  
      AVPacket enc_pkt;
  
      int(*enc_func)(AVCodecContext *, AVPacket *, const AVFrame *, int *) =
  
          (ifmt_ctx->streams[stream_index]->codecpar->codec_type ==
  
              AVMEDIA_TYPE_VIDEO) ? avcodec_encode_video2 : avcodec_encode_audio2;
  
  
  
      if (!got_frame)
  
          got_frame = &amp;got_frame_local;
  
  
  
      // av_log(NULL, AV_LOG_INFO, "Encoding frame\n");
  
      /* encode filtered frame */
  
      enc_pkt.data = NULL;
  
      enc_pkt.size = 0;
  
      av_init_packet(&amp;enc_pkt);
  
  
  
      ret = enc_func(stream_ctx[stream_index].enc_ctx, &amp;enc_pkt,
  
          filt_frame, got_frame);
  
  
  
      av_frame_free(&amp;filt_frame);
  
      if (ret &lt; 0)
  
          return ret;
  
      if (!(*got_frame))
  
          return 0;
  
  
  
      /* prepare packet for muxing */
  
      /*enc_pkt.stream_index = stream_index;
  
      av_packet_rescale_ts(&amp;enc_pkt, stream_ctx[stream_index].enc_ctx->time_base, ofmt_ctx->streams[stream_index]->time_base);*/
  
      enc_pkt.stream_index = 0;
  
      av_packet_rescale_ts(&amp;enc_pkt, stream_ctx[stream_index].enc_ctx->time_base, ofmt_ctx->streams[0]->time_base);
  
  
  
      av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");
  
      /* mux encoded frame */
  
      ret = av_interleaved_write_frame(ofmt_ctx, &amp;enc_pkt);
  
      return ret;
  
  }
  
  
  
  static int filter_encode_write_frame(AVFrame *frame, unsigned int stream_index, const int videoStreamIndex)
  
  {
  
      // Just video, all else crashes
  
      if (stream_index != videoStreamIndex)
  
          return 0;
  
  
  
      int ret;
  
      AVFrame *filt_frame;
  
  
  
      // av_log(NULL, AV_LOG_INFO, "Pushing decoded frame to filters\n");
  
      /* push the decoded frame into the filtergraph */
  
      ret = av_buffersrc_add_frame_flags(filter_ctx[stream_index].buffersrc_ctx,
  
          frame, 0);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
  
          return ret;
  
      }
  
  
  
      /* pull filtered frames from the filtergraph */
  
      while (1) {
  
          filt_frame = av_frame_alloc();
  
          if (!filt_frame) {
  
              ret = AVERROR(ENOMEM);
  
              break;
  
          }
  
          // av_log(NULL, AV_LOG_INFO, "Pulling filtered frame from filters\n");
  
          ret = av_buffersink_get_frame(filter_ctx[stream_index].buffersink_ctx,
  
              filt_frame);
  
          if (ret &lt; 0) {
  
              /* if no more frames for output - returns AVERROR(EAGAIN)
  
              * if flushed and no more frames for output - returns AVERROR_EOF
  
              * rewrite retcode to 0 to show it as normal procedure completion
  
              */
  
              if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
                  ret = 0;
  
              av_frame_free(&amp;filt_frame);
  
              break;
  
          }
  
  
  
          filt_frame->pict_type = AV_PICTURE_TYPE_NONE;
  
          ret = encode_write_frame(filt_frame, stream_index, NULL, videoStreamIndex);
  
          if (ret &lt; 0)
  
              break;
  
      }
  
  
  
      return ret;
  
  }
  
  
  
  static int flush_encoder(unsigned int stream_index, const int videoStreamIndex)
  
  {
  
      int ret;
  
      int got_frame;
  
  
  
      // Just video
  
      if (stream_index != videoStreamIndex)
  
          return 0;
  
  
  
      if (!(stream_ctx[stream_index].enc_ctx->codec->capabilities &amp;
  
          AV_CODEC_CAP_DELAY))
  
          return 0;
  
  
  
      while (1) {
  
          av_log(NULL, AV_LOG_INFO, "Flushing stream #%u encoder\n", stream_index);
  
          ret = encode_write_frame(NULL, stream_index, &amp;got_frame, videoStreamIndex);
  
          if (ret &lt; 0)
  
              break;
  
          if (!got_frame)
  
              return 0;
  
      }
  
      return ret;
  
  }
  
  
  
  
  
  #include <vector>
  
  
  
  int main(int argc, char **argv)
  
  {
  
      int ret;
  
  
  
      AVPacket packet;
  
      packet.data = NULL;
  
      packet.size = 0;
  
  
  
      AVFrame *frame = NULL;
  
      enum AVMediaType type;
  
      unsigned int stream_index;
  
      unsigned int i;
  
      int got_frame;
  
      int(*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket *);
  
  
  
  
  
  #ifdef _DEBUG
  
      // Hardcoded arguments
  
      std::vector varguments;
  
      {
  
          varguments.push_back(argv[0]);
  
  
  
          // Source
  
          varguments.push_back("./big_buck_bunny_short.mp4 ");
  
  
  
          // Destination
  
          varguments.push_back("./big_buck_bunny_short-processed.mp4");
  
      }
  
  
  
      char** arguments = new char*[varguments.size()];
  
      for (unsigned int i = 0; i &lt; varguments.size(); i++)
  
      {
  
          arguments[i] = varguments[i];
  
      }
  
      argc = varguments.size();
  
      argv = arguments;
  
  #endif // _DEBUG
  
  
  
  
  
      if (argc != 3) {
  
          av_log(NULL, AV_LOG_ERROR, "Usage: %s <input file="file" /> <output file="file">\n", argv[0]);
  
          return 1;
  
      }
  
  
  
      av_register_all();
  
      avfilter_register_all();
  
  
  
      int videoStreamIndex = -1;
  
      if ((ret = open_input_file(argv[1], videoStreamIndex)) &lt; 0)
  
          goto end;
  
      if ((ret = open_output_file(argv[2], videoStreamIndex)) &lt; 0)
  
          goto end;
  
      if ((ret = init_filters(videoStreamIndex)) &lt; 0)
  
          goto end;
  
  
  
      // Stop after a couple of frames
  
      int framesToGet = 100;
  
  
  
      /* read all packets */
  
      //while (framesToGet--)
  
      while(1)
  
      {
  
          if ((ret = av_read_frame(ifmt_ctx, &amp;packet)) &lt; 0)
  
              break;
  
          stream_index = packet.stream_index;
  
  
  
          // I just need video
  
          if (stream_index != videoStreamIndex) {
  
              av_packet_unref(&amp;packet);
  
              continue;
  
          }
  
  
  
          type = ifmt_ctx->streams[packet.stream_index]->codecpar->codec_type;
  
          av_log(NULL, AV_LOG_DEBUG, "Demuxer gave frame of stream_index %u\n",
  
              stream_index);
  
  
  
          if (filter_ctx[stream_index].filter_graph) {
  
              av_log(NULL, AV_LOG_DEBUG, "Going to reencode&amp;filter the frame\n");
  
              frame = av_frame_alloc();
  
              if (!frame) {
  
                  ret = AVERROR(ENOMEM);
  
                  break;
  
              }
  
              av_packet_rescale_ts(&amp;packet,
  
                  ifmt_ctx->streams[stream_index]->time_base,
  
                  stream_ctx[stream_index].dec_ctx->time_base);
  
              dec_func = (type == AVMEDIA_TYPE_VIDEO) ? avcodec_decode_video2 :
  
                  avcodec_decode_audio4;
  
              ret = dec_func(stream_ctx[stream_index].dec_ctx, frame,
  
                  &amp;got_frame, &amp;packet);
  
              if (ret &lt; 0) {
  
                  av_frame_free(&amp;frame);
  
                  av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");
  
                  break;
  
              }
  
  
  
              if (got_frame) {
  
                  frame->pts = frame->best_effort_timestamp;
  
                  ret = filter_encode_write_frame(frame, stream_index, videoStreamIndex);
  
                  av_frame_free(&amp;frame);
  
                  if (ret &lt; 0)
  
                      goto end;
  
              }
  
              else {
  
                  av_frame_free(&amp;frame);
  
              }
  
          }
  
          else {
  
              /* remux this frame without reencoding */
  
              av_packet_rescale_ts(&amp;packet,
  
                  ifmt_ctx->streams[stream_index]->time_base,
  
                  ofmt_ctx->streams[stream_index]->time_base);
  
  
  
              ret = av_interleaved_write_frame(ofmt_ctx, &amp;packet);
  
              if (ret &lt; 0)
  
                  goto end;
  
          }
  
          av_packet_unref(&amp;packet);
  
      }
  
  
  
      /* flush filters and encoders */
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          /* flush filter */
  
          if (!filter_ctx[i].filter_graph)
  
              continue;
  
          ret = filter_encode_write_frame(NULL, i, videoStreamIndex);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Flushing filter failed\n");
  
              goto end;
  
          }
  
  
  
          /* flush encoder */
  
          ret = flush_encoder(i, videoStreamIndex);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");
  
              goto end;
  
          }
  
      }
  
  
  
      av_write_trailer(ofmt_ctx);
  
  end:
  
      av_packet_unref(&amp;packet);
  
      av_frame_free(&amp;frame);
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          // Just video
  
          if (i != videoStreamIndex)
  
              continue;
  
          avcodec_free_context(&amp;stream_ctx[i].dec_ctx);
  
          if (ofmt_ctx &amp;&amp; ofmt_ctx->nb_streams > i &amp;&amp; ofmt_ctx->streams[i] &amp;&amp; stream_ctx[i].enc_ctx)
  
              avcodec_free_context(&amp;stream_ctx[i].enc_ctx);
  
          if (filter_ctx &amp;&amp; filter_ctx[i].filter_graph)
  
              avfilter_graph_free(&amp;filter_ctx[i].filter_graph);
  
      }
  
      av_free(filter_ctx);
  
      av_free(stream_ctx);
  
      avformat_close_input(&amp;ifmt_ctx);
  
      if (ofmt_ctx &amp;&amp; !(ofmt_ctx->oformat->flags &amp; AVFMT_NOFILE))
  
          avio_closep(&amp;ofmt_ctx->pb);
  
      avformat_free_context(ofmt_ctx);
  
  
  
      /*if (ret &lt; 0)
  
          av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret));*/
  
  
  
      return ret ? 1 : 0;
  
  }
  
  </output></vector>

• Easily track Events within Matomo Analytics thanks to Matomo Tag Manager

  7 juin 2019, par Matomo Core Team — Analytics Tips

  Easily track Events within Matomo Analytics thanks to Matomo Tag Manager

  Introduction

  In this article we’ll cover what events in Matomo Analytics are ; and how you can easily set them up thanks to Matomo Tag Manager.

  Key concepts within this article

  • Events
  • Quick definition of the Tag Management System
  • Matomo config
  • Creating triggers
  • Variables

  What are events in Matomo Analytics and why are they useful ?

  Events allow you to measure interactions on your website which are not defined by default. With them you can measure clicks on some elements of a page, such as, how visitors are interacting with dropdown menus, media players, scrolling behaviours etc. You can also use them to define goals which make them a key feature in Matomo Analytics. Learn more about tracking events in Matomo.

  You can easily access the Events report in Matomo Analytics by clicking on the Behaviour category :

  

  And you may read the following message and feel a bit frustrated :

  

  “There is no data for this report” is a nice way to say, “Hey, you are tracking just a tiny part of what Matomo Analytics can do for you.”

  Matomo is a great software, but it can’t guess what you want to track.

  In order for Matomo to register those event tracking interactions, you’ll need to explain it by adding a line of code similar to this one when the interaction happens :

   

  _paq.push(['trackEvent', 'Here you enter whatever you want', 'Here too', 'and here also']);

   

  Let’s imagine you want to track a click on an HTML button, your code will look something similar to this at the moment of the interaction :

  Click Me !

  As you can imagine, two main challenges will arise for non developers :

  1. How to access the source code ?
  2. How to define the interaction ?

  Luckily, Matomo Tag Manager makes those steps easy for you. Let’s see how the same tracking is implemented with Matomo Tag Manager.

  A quick definition of what Matomo Tag Manager is

  Matomo Tag Manager lets you manage all your tracking and marketing tags in one easy-to-access place. Please visit this page to learn more about Matomo Tag Manager. In order to start using it, you’ll need to copy/paste a tracking code, named a “container”, within the section of your pages.

  Once the container is on your website, all you need to do is to follow these simple steps :

  1. Add a Matomo Tag.
  2. Assign the condition to fire the tag (what we call the trigger).
  3. Publish your work.
  4. And enjoy

  1 – Add a Matomo Event tracking code

  All you have to do here is click on “CREATE NEW TAG”

  

  Once selected, just mention how you’d like this tag to be named (it is for your internal purpose here so always use an explicit tag name) and the Matomo configuration (the default configuration setting will be fine in most of the cases) :

  

  Then Matomo Tag Manager will ask you the type of tracking you’d like to deploy, in this case, this is an event so select “Event” :

  

  Then all you need is to indicate the values you’d like to push through your event :

  

  To put it in perspective, all we did here through Matomo Tag Manager was implement the equivalent of the following line of code :

  _paq.push(['trackEvent', 'Element interactions', 'Click button', 'Click Me']);

  Let’s now see how can we do this on click code part which we call a trigger.

  2 – Assign the condition to fire the tag

  In order to execute the event we’ll need to define when it will happen. You do this by clicking on Create a new trigger now :

  

  As the interaction we’d like to track is happening when a click occurs, it will be a click trigger, and as our button is not a link, we’ll select All Elements Click :

  

  Once selected you’ll need to be precise on the condition in which the event will be triggered. In this case we do not want to have events pushed every time someone is clicking on something on our website. We only want to track when they click on this specific button. That’s the reason why our trigger is set to fire only when the click occurs on an element which has an id and has the value “cta” :

  Once you click on the green button named CREATE NEW TRIGGER, you validate the tag by clicking on CREATE NEW TAG :

  

  

  Then you can move to the last part.

  3 – Publish your work

  Tag Managers are very powerful as they allow you to easily execute any JavaScript code, CSS or even text content on your websites.

  That’s why when you create your tag it doesn’t go live straight away on your website. In order to do this you need to publish your tag and this is what the “Publish” category is designed for :

  

  After that, click on the second button if you’re confident your tag and trigger are both ready to go live :

  

  4 – Enjoy

  Well done. As your tag is now live, every click made on this button will now be pushed to your Matomo Analytics account within :
  

  1. The visitor log report :

  

  2. The events report :

  

  You may now be asking, “That’s great, but can I collect something more exciting than clicks ?” 

  Of course you can ! This is what the Matomo Tag Manager is all about.

  As long as you can express it through a trigger you can really push whatever you want to Matomo Analytics. You can track scrolling patterns, an element visible on the page like an image, an ad or the time spent on the page. The options are now open to you with Tag Manager.

  Give them a try ! Change the triggers, start playing around with variables and discover that the possibilities are endless.

  Happy analytics,
  Matomo team

• RTSP relay using ffmpeg library

  23 novembre 2015, par kiran_g

  I am implementing an RTSP relay using libavcodec (ffmpeg). Basically, it connects to an IP camera, which is an RTSP server, PULLs the stream and then PUSHes it to wowza. I am finding it very difficult to get any sample implementation for this in the internet. So I started implementing this using bits and pieces from here and there. I took code for code samples to a) read RTSP stream and write to file b)read from file and serve it over RTSP.

  This is the current state of the code :

  /*
  
   * Copyright (c) 2010 Nicolas George
  
   * Copyright (c) 2011 Stefano Sabatini
  
   * Copyright (c) 2014 Andrey Utkin
  
   *
  
   * Permission is hereby granted, free of charge, to any person obtaining a copy
  
   * of this software and associated documentation files (the "Software"), to deal
  
   * in the Software without restriction, including without limitation the rights
  
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  
   * copies of the Software, and to permit persons to whom the Software is
  
   * furnished to do so, subject to the following conditions:
  
   *
  
   * The above copyright notice and this permission notice shall be included in
  
   * all copies or substantial portions of the Software.
  
   *
  
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  
   * THE SOFTWARE.
  
   */
  
  
  
  /**
  
   * @file
  
   * API example for demuxing, decoding, filtering, encoding and muxing
  
   * @example transcoding.c
  
   */
  
  
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavfilter></libavfilter>avfiltergraph.h>
  
  #include <libavfilter></libavfilter>buffersink.h>
  
  #include <libavfilter></libavfilter>buffersrc.h>
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavutil></libavutil>pixdesc.h>
  
  
  
  static AVFormatContext *ifmt_ctx,*temp;
  
  static AVFormatContext *ofmt_ctx;
  
  typedef struct FilteringContext {
  
      AVFilterContext *buffersink_ctx;
  
      AVFilterContext *buffersrc_ctx;
  
      AVFilterGraph *filter_graph;
  
  } FilteringContext;
  
  static FilteringContext *filter_ctx;
  
  
  
  static int open_input_file(const char *filename)
  
  {
  
      int ret;
  
      unsigned int i;
  
  
  
      ifmt_ctx = NULL;
  
      if ((ret = avformat_open_input(&amp;ifmt_ctx, filename, NULL, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
  
          return ret;
  
      }
  
  
  
      if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
  
          return ret;
  
      }
  
  
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          AVStream *stream;
  
          AVCodecContext *codec_ctx;
  
          stream = ifmt_ctx->streams[i];
  
          codec_ctx = stream->codec;
  
          /* Reencode video &amp; audio and remux subtitles etc. */
  
          if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
  
                  || codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
  
              /* Open decoder */
  
              ret = avcodec_open2(codec_ctx,
  
                      avcodec_find_decoder(codec_ctx->codec_id), NULL);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);
  
                  return ret;
  
              }
  
          }
  
      }
  
  
  
      av_dump_format(ifmt_ctx, 0, filename, 0);
  
      return 0;
  
  }
  
  
  
  static int open_output_file(const char *filename)
  
  {
  
      AVStream *out_stream;
  
      AVStream *in_stream;
  
      AVCodecContext *dec_ctx, *enc_ctx;
  
      AVCodec *encoder,*codec;
  
      int ret;
  
      unsigned int i;
  
  
  
      ofmt_ctx = NULL;
  
      avformat_open_input(&amp;temp, "rtsp://localhost:8554/live", NULL, NULL);
  
      avformat_alloc_output_context2(&amp;ofmt_ctx, temp->oformat,"rtsp", filename);
  
      if (!ofmt_ctx) {
  
          av_log(NULL, AV_LOG_ERROR, "Could not create output context\n");
  
          return AVERROR_UNKNOWN;
  
      }
  
  
  
  
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          out_stream = avformat_new_stream(ofmt_ctx, NULL);
  
          if (!out_stream) {
  
              av_log(NULL, AV_LOG_ERROR, "Failed allocating output stream\n");
  
              return AVERROR_UNKNOWN;
  
          }
  
  
  
          in_stream = ifmt_ctx->streams[i];
  
          dec_ctx = in_stream->codec;
  
          enc_ctx = out_stream->codec;
  
  
  
          if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
  
                  || dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
  
              /* in this example, we choose transcoding to same codec */
  
              encoder = avcodec_find_encoder(dec_ctx->codec_id);
  
              printf("codec : %d",dec_ctx->codec_id);
  
              if (!encoder) {
  
                  av_log(NULL, AV_LOG_FATAL, "Necessary encoder not found\n");
  
                  return AVERROR_INVALIDDATA;
  
              }
  
  
  
              /* In this example, we transcode to same properties (picture size,
  
               * sample rate etc.). These properties can be changed for output
  
               * streams easily using filters */
  
              if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
  
                  enc_ctx->height = dec_ctx->height;
  
                  enc_ctx->width = dec_ctx->width;
  
                  enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
  
                  /* take first format from list of supported formats */
  
                  enc_ctx->pix_fmt = encoder->pix_fmts[0];
  
                  //enc_ctx->codec_id = AV_CODEC_ID_H264;
  
                  /* video time_base can be set to whatever is handy and supported by encoder */
  
                  enc_ctx->time_base = dec_ctx->time_base;
  
              } else {
  
                  enc_ctx->sample_rate = dec_ctx->sample_rate;
  
                  enc_ctx->channel_layout = dec_ctx->channel_layout;
  
                  enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
  
                  /* take first format from list of supported formats */
  
                  enc_ctx->sample_fmt = encoder->sample_fmts[0];
  
                  enc_ctx->pix_fmt =AV_PIX_FMT_RGB24 ;
  
                  enc_ctx->time_base = (AVRational){1, enc_ctx->sample_rate};
  
              }
  
  
  
              /* Third parameter can be used to pass settings to encoder */
  
              //codec = avcodec_find_encoder(AV_CODEC_ID_H264);
  
              ret = avcodec_open2(enc_ctx, encoder, NULL);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);
  
                  return ret;
  
              }
  
          } else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) {
  
              av_log(NULL, AV_LOG_FATAL, "Elementary stream #%d is of unknown type, cannot proceed\n", i);
  
              return AVERROR_INVALIDDATA;
  
          } else {
  
              /* if this stream must be remuxed */
  
              ret = avcodec_copy_context(ofmt_ctx->streams[i]->codec,
  
                      ifmt_ctx->streams[i]->codec);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Copying stream context failed\n");
  
                  return ret;
  
              }
  
          }
  
  
  
          if (ofmt_ctx->oformat->flags &amp; AVFMT_GLOBALHEADER)
  
              enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      }
  
      av_dump_format(ofmt_ctx, 0, filename, 1);
  
  
  
      if (!(ofmt_ctx->oformat->flags &amp; AVFMT_NOFILE)) {
  
          ret = avio_open(&amp;ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Could not open output file '%s'", filename);
  
              return ret;
  
          }
  
      }
  
  
  
      /* init muxer, write output file header */
  
      ret = avformat_write_header(ofmt_ctx, NULL);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Error occurred when opening output file\n");
  
          return ret;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  static int init_filter(FilteringContext* fctx, AVCodecContext *dec_ctx,
  
          AVCodecContext *enc_ctx, const char *filter_spec)
  
  {
  
      char args[512];
  
      int ret = 0;
  
      AVFilter *buffersrc = NULL;
  
      AVFilter *buffersink = NULL;
  
      AVFilterContext *buffersrc_ctx = NULL;
  
      AVFilterContext *buffersink_ctx = NULL;
  
      AVFilterInOut *outputs = avfilter_inout_alloc();
  
      AVFilterInOut *inputs  = avfilter_inout_alloc();
  
      AVFilterGraph *filter_graph = avfilter_graph_alloc();
  
  
  
      if (!outputs || !inputs || !filter_graph) {
  
          ret = AVERROR(ENOMEM);
  
          goto end;
  
      }
  
  
  
      if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
  
          buffersrc = avfilter_get_by_name("buffer");
  
          buffersink = avfilter_get_by_name("buffersink");
  
          if (!buffersrc || !buffersink) {
  
              av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
  
              ret = AVERROR_UNKNOWN;
  
              goto end;
  
          }
  
  
  
          snprintf(args, sizeof(args),
  
                  "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
  
                  dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
  
                  dec_ctx->time_base.num, dec_ctx->time_base.den,
  
                  dec_ctx->sample_aspect_ratio.num,
  
                  dec_ctx->sample_aspect_ratio.den);
  
  
  
          ret = avfilter_graph_create_filter(&amp;buffersrc_ctx, buffersrc, "in",
  
                  args, NULL, filter_graph);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
  
              goto end;
  
          }
  
  
  
          ret = avfilter_graph_create_filter(&amp;buffersink_ctx, buffersink, "out",
  
                  NULL, NULL, filter_graph);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
  
              goto end;
  
          }
  
  
  
          ret = av_opt_set_bin(buffersink_ctx, "pix_fmts",
  
                  (uint8_t*)&amp;enc_ctx->pix_fmt, sizeof(enc_ctx->pix_fmt),
  
                  AV_OPT_SEARCH_CHILDREN);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
  
              goto end;
  
          }
  
      } else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
  
          buffersrc = avfilter_get_by_name("abuffer");
  
          buffersink = avfilter_get_by_name("abuffersink");
  
          if (!buffersrc || !buffersink) {
  
              av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
  
              ret = AVERROR_UNKNOWN;
  
              goto end;
  
          }
  
  
  
          if (!dec_ctx->channel_layout)
  
              dec_ctx->channel_layout =
  
                  av_get_default_channel_layout(dec_ctx->channels);
  
          snprintf(args, sizeof(args),
  
                  "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
  
                  dec_ctx->time_base.num, dec_ctx->time_base.den, dec_ctx->sample_rate,
  
                  av_get_sample_fmt_name(dec_ctx->sample_fmt),
  
                  dec_ctx->channel_layout);
  
          ret = avfilter_graph_create_filter(&amp;buffersrc_ctx, buffersrc, "in",
  
                  args, NULL, filter_graph);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
  
              goto end;
  
          }
  
  
  
          ret = avfilter_graph_create_filter(&amp;buffersink_ctx, buffersink, "out",
  
                  NULL, NULL, filter_graph);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
  
              goto end;
  
          }
  
  
  
          ret = av_opt_set_bin(buffersink_ctx, "sample_fmts",
  
                  (uint8_t*)&amp;enc_ctx->sample_fmt, sizeof(enc_ctx->sample_fmt),
  
                  AV_OPT_SEARCH_CHILDREN);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
  
              goto end;
  
          }
  
  
  
          ret = av_opt_set_bin(buffersink_ctx, "channel_layouts",
  
                  (uint8_t*)&amp;enc_ctx->channel_layout,
  
                  sizeof(enc_ctx->channel_layout), AV_OPT_SEARCH_CHILDREN);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
  
              goto end;
  
          }
  
  
  
          ret = av_opt_set_bin(buffersink_ctx, "sample_rates",
  
                  (uint8_t*)&amp;enc_ctx->sample_rate, sizeof(enc_ctx->sample_rate),
  
                  AV_OPT_SEARCH_CHILDREN);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
  
              goto end;
  
          }
  
      } else {
  
          ret = AVERROR_UNKNOWN;
  
          goto end;
  
      }
  
  
  
      /* Endpoints for the filter graph. */
  
      outputs->name       = av_strdup("in");
  
      outputs->filter_ctx = buffersrc_ctx;
  
      outputs->pad_idx    = 0;
  
      outputs->next       = NULL;
  
  
  
      inputs->name       = av_strdup("out");
  
      inputs->filter_ctx = buffersink_ctx;
  
      inputs->pad_idx    = 0;
  
      inputs->next       = NULL;
  
  
  
      if (!outputs->name || !inputs->name) {
  
          ret = AVERROR(ENOMEM);
  
          goto end;
  
      }
  
  
  
      if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_spec,
  
                      &amp;inputs, &amp;outputs, NULL)) &lt; 0)
  
          goto end;
  
  
  
      if ((ret = avfilter_graph_config(filter_graph, NULL)) &lt; 0)
  
          goto end;
  
  
  
      /* Fill FilteringContext */
  
      fctx->buffersrc_ctx = buffersrc_ctx;
  
      fctx->buffersink_ctx = buffersink_ctx;
  
      fctx->filter_graph = filter_graph;
  
  
  
  end:
  
      avfilter_inout_free(&amp;inputs);
  
      avfilter_inout_free(&amp;outputs);
  
  
  
      return ret;
  
  }
  
  
  
  static int init_filters(void)
  
  {
  
      const char *filter_spec;
  
      unsigned int i;
  
      int ret;
  
      filter_ctx = av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));
  
      if (!filter_ctx)
  
          return AVERROR(ENOMEM);
  
  
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          filter_ctx[i].buffersrc_ctx  = NULL;
  
          filter_ctx[i].buffersink_ctx = NULL;
  
          filter_ctx[i].filter_graph   = NULL;
  
          if (!(ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO
  
                  || ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO))
  
              continue;
  
  
  
  
  
          if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
  
              filter_spec = "null"; /* passthrough (dummy) filter for video */
  
          else
  
              filter_spec = "anull"; /* passthrough (dummy) filter for audio */
  
          ret = init_filter(&amp;filter_ctx[i], ifmt_ctx->streams[i]->codec,
  
                  ofmt_ctx->streams[i]->codec, filter_spec);
  
          if (ret)
  
              return ret;
  
      }
  
      return 0;
  
  }
  
  
  
  static int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index, int *got_frame) {
  
      int ret;
  
      int got_frame_local;
  
      AVPacket enc_pkt;
  
      int (*enc_func)(AVCodecContext *, AVPacket *, const AVFrame *, int *) =
  
          (ifmt_ctx->streams[stream_index]->codec->codec_type ==
  
           AVMEDIA_TYPE_VIDEO) ? avcodec_encode_video2 : avcodec_encode_audio2;
  
  
  
      if (!got_frame)
  
          got_frame = &amp;got_frame_local;
  
  
  
      av_log(NULL, AV_LOG_INFO, "Encoding frame\n");
  
      /* encode filtered frame */
  
      enc_pkt.data = NULL;
  
      enc_pkt.size = 0;
  
      av_init_packet(&amp;enc_pkt);
  
      ret = enc_func(ofmt_ctx->streams[stream_index]->codec, &amp;enc_pkt,
  
              filt_frame, got_frame);
  
      av_frame_free(&amp;filt_frame);
  
      if (ret &lt; 0)
  
          return ret;
  
      if (!(*got_frame))
  
          return 0;
  
  
  
      /* prepare packet for muxing */
  
      enc_pkt.stream_index = stream_index;
  
      av_packet_rescale_ts(&amp;enc_pkt,
  
                           ofmt_ctx->streams[stream_index]->codec->time_base,
  
                           ofmt_ctx->streams[stream_index]->time_base);
  
  
  
      av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");
  
      /* mux encoded frame */
  
      ret = av_interleaved_write_frame(ofmt_ctx, &amp;enc_pkt);
  
      return ret;
  
  }
  
  
  
  static int filter_encode_write_frame(AVFrame *frame, unsigned int stream_index)
  
  {
  
      int ret;
  
      AVFrame *filt_frame;
  
  
  
      av_log(NULL, AV_LOG_INFO, "Pushing decoded frame to filters\n");
  
      /* push the decoded frame into the filtergraph */
  
      ret = av_buffersrc_add_frame_flags(filter_ctx[stream_index].buffersrc_ctx,
  
              frame, 0);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
  
          return ret;
  
      }
  
  
  
      /* pull filtered frames from the filtergraph */
  
      while (1) {
  
          filt_frame = av_frame_alloc();
  
          if (!filt_frame) {
  
              ret = AVERROR(ENOMEM);
  
              break;
  
          }
  
          av_log(NULL, AV_LOG_INFO, "Pulling filtered frame from filters\n");
  
          ret = av_buffersink_get_frame(filter_ctx[stream_index].buffersink_ctx,
  
                  filt_frame);
  
          if (ret &lt; 0) {
  
              /* if no more frames for output - returns AVERROR(EAGAIN)
  
               * if flushed and no more frames for output - returns AVERROR_EOF
  
               * rewrite retcode to 0 to show it as normal procedure completion
  
               */
  
              if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
                  ret = 0;
  
              av_frame_free(&amp;filt_frame);
  
              break;
  
          }
  
  
  
          filt_frame->pict_type = AV_PICTURE_TYPE_NONE;
  
          ret = encode_write_frame(filt_frame, stream_index, NULL);
  
          if (ret &lt; 0)
  
              break;
  
      }
  
  
  
      return ret;
  
  }
  
  
  
  static int flush_encoder(unsigned int stream_index)
  
  {
  
      int ret;
  
      int got_frame;
  
  
  
      if (!(ofmt_ctx->streams[stream_index]->codec->codec->capabilities &amp;
  
                  AV_CODEC_CAP_DELAY))
  
          return 0;
  
  
  
      while (1) {
  
          av_log(NULL, AV_LOG_INFO, "Flushing stream #%u encoder\n", stream_index);
  
          ret = encode_write_frame(NULL, stream_index, &amp;got_frame);
  
          if (ret &lt; 0)
  
              break;
  
          if (!got_frame)
  
              return 0;
  
      }
  
      return ret;
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      int ret;
  
      AVPacket packet = { .data = NULL, .size = 0 };
  
      AVFrame *frame = NULL;
  
      enum AVMediaType type;
  
      unsigned int stream_index;
  
      unsigned int i;
  
      int got_frame;
  
      int (*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket *);
  
  
  
      if (argc != 3) {
  
          av_log(NULL, AV_LOG_ERROR, "Usage: %s <input file="file" /> <output file="file">\n", argv[0]);
  
          return 1;
  
      }
  
  
  
      av_register_all();
  
      avfilter_register_all();
  
      avformat_network_init();
  
  
  
      if ((ret = open_input_file(argv[1])) &lt; 0)
  
          goto end;
  
      if ((ret = open_output_file(argv[2])) &lt; 0)
  
          goto end;
  
      if ((ret = init_filters()) &lt; 0)
  
          goto end;
  
  
  
      /* read all packets */
  
      while (1) {
  
          if ((ret = av_read_frame(ifmt_ctx, &amp;packet)) &lt; 0)
  
              break;
  
          stream_index = packet.stream_index;
  
          type = ifmt_ctx->streams[packet.stream_index]->codec->codec_type;
  
          av_log(NULL, AV_LOG_DEBUG, "Demuxer gave frame of stream_index %u\n",
  
                  stream_index);
  
  
  
          if (filter_ctx[stream_index].filter_graph) {
  
              av_log(NULL, AV_LOG_DEBUG, "Going to reencode&amp;filter the frame\n");
  
              frame = av_frame_alloc();
  
              if (!frame) {
  
                  ret = AVERROR(ENOMEM);
  
                  break;
  
              }
  
              av_packet_rescale_ts(&amp;packet,
  
                                   ifmt_ctx->streams[stream_index]->time_base,
  
                                   ifmt_ctx->streams[stream_index]->codec->time_base);
  
              dec_func = (type == AVMEDIA_TYPE_VIDEO) ? avcodec_decode_video2 :
  
                  avcodec_decode_audio4;
  
              ret = dec_func(ifmt_ctx->streams[stream_index]->codec, frame,
  
                      &amp;got_frame, &amp;packet);
  
              if (ret &lt; 0) {
  
                  av_frame_free(&amp;frame);
  
                  av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");
  
                  break;
  
              }
  
  
  
              if (got_frame) {
  
                  frame->pts = av_frame_get_best_effort_timestamp(frame);
  
                  ret = filter_encode_write_frame(frame, stream_index);
  
                  av_frame_free(&amp;frame);
  
                  if (ret &lt; 0)
  
                      goto end;
  
              } else {
  
                  av_frame_free(&amp;frame);
  
              }
  
          } else {
  
              /* remux this frame without reencoding */
  
              av_packet_rescale_ts(&amp;packet,
  
                                   ifmt_ctx->streams[stream_index]->time_base,
  
                                   ofmt_ctx->streams[stream_index]->time_base);
  
  
  
              ret = av_interleaved_write_frame(ofmt_ctx, &amp;packet);
  
              if (ret &lt; 0)
  
                  goto end;
  
          }
  
          av_packet_unref(&amp;packet);
  
      }
  
  
  
      /* flush filters and encoders */
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          /* flush filter */
  
          if (!filter_ctx[i].filter_graph)
  
              continue;
  
          ret = filter_encode_write_frame(NULL, i);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Flushing filter failed\n");
  
              goto end;
  
          }
  
  
  
          /* flush encoder */
  
          ret = flush_encoder(i);
  
          if (ret &lt; 0) {
  
              av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");
  
              goto end;
  
          }
  
      }
  
  
  
      av_write_trailer(ofmt_ctx);
  
  end:
  
      av_packet_unref(&amp;packet);
  
      av_frame_free(&amp;frame);
  
      for (i = 0; i &lt; ifmt_ctx->nb_streams; i++) {
  
          avcodec_close(ifmt_ctx->streams[i]->codec);
  
          if (ofmt_ctx &amp;&amp; ofmt_ctx->nb_streams > i &amp;&amp; ofmt_ctx->streams[i] &amp;&amp; ofmt_ctx->streams[i]->codec)
  
              avcodec_close(ofmt_ctx->streams[i]->codec);
  
          if (filter_ctx &amp;&amp; filter_ctx[i].filter_graph)
  
              avfilter_graph_free(&amp;filter_ctx[i].filter_graph);
  
      }
  
      av_free(filter_ctx);
  
      avformat_close_input(&amp;ifmt_ctx);
  
      if (ofmt_ctx &amp;&amp; !(ofmt_ctx->oformat->flags &amp; AVFMT_NOFILE))
  
          avio_closep(&amp;ofmt_ctx->pb);
  
      avformat_free_context(ofmt_ctx);
  
  
  
      if (ret &lt; 0)
  
          av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret));
  
  
  
      return ret ? 1 : 0;
  
  }
  
  </output>

  When we run this we are getting this error :

  Input #0, rtsp, from 'rtsp://localhost:8554/live':
  
    Metadata:
  
      title           : Unnamed
  
      comment         : N/A
  
    Duration: N/A, start: 5294.642467, bitrate: N/A
  
      Stream #0:0: Video: h264 (Constrained Baseline), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 30 fps, 30 tbr, 90k tbn, 60 tbc
  
  [libx264 @ 0xe87c80] Specified pixel format -1 is invalid or not supported
  
  Cannot open video encoder for stream #0
  
  codec : 28 and pix :12
  
  Error occurred: Invalid argument

  But I could see that the correct pixel format macro "AV_PIX_FMT_YUV420P" is provided.

  UPDATE 1 :
  This is the section in ffmpeg where the error is thrown from(utils.c line 1547) :

   if (avctx->codec->pix_fmts) {
  
              for (i = 0; avctx->codec->pix_fmts[i] != AV_PIX_FMT_NONE; i++)
  
                  if (avctx->pix_fmt == avctx->codec->pix_fmts[i])
  
                      break;
  
              if (avctx->codec->pix_fmts[i] == AV_PIX_FMT_NONE
  
                  && !((avctx->codec_id == AV_CODEC_ID_MJPEG || avctx->codec_id == AV_CODEC_ID_LJPEG)
  
                       && avctx->strict_std_compliance <= FF_COMPLIANCE_UNOFFICIAL)) {
  
                  char buf[128];
  
                  snprintf(buf, sizeof(buf), "%d", avctx->pix_fmt);
  
                  av_log(avctx, AV_LOG_ERROR, "Specified pixel format %s is invalid or not supported\n",
  
                         (char *)av_x_if_null(av_get_pix_fmt_name(avctx->pix_fmt), buf));
  
                  ret = AVERROR(EINVAL);
  
                  goto free_and_end;
  
              }

  Can someone suggest a solution for this.

  Thanks