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• How to update MP4 with the video length

  9 décembre 2015, par oygle

  I used youtube-dl to obtain a friends video. When I play it in VLC, I notice there is no time/length shown. As we need to cut part of this video with ffmpeg, can I use ffmpeg (or similar tool) to determine the length of the video, and then update the MP4 to contain the time/length ?

• Image to MPEG on Linux works, same code on Android = green video

  27 novembre 2014, par JScoobyCed

  EDIT
  I have check the execution and found that the error is not (yet) at the swscale point. My current issue is that the JPG image is not found :
  No such file or directory
  when doing the avformat_open_input(&pFormatCtx, imageFileName, NULL, NULL);
  Before you tell me I need to register anything, I can tell I already did (I updated the code below).
  I also added the Android permission to access the external storage (I don’t think it is related to Android since I can already write to the /mnt/sdcard/ where the image is also located)
  END EDIT

  I have been through several tutorials (including the few posted from SO, i.e. http://dranger.com/ffmpeg/, how to compile ffmpeg for Android...,been through dolphin-player source code). Here is what I have :
  . Compiled ffmpeg for android
  . Ran basic tutorials using NDK to create a dummy video on my android device
  . been able to generate a MPEG2 video from images on Ubuntu using a modified version of dummy video code above and a lot of Googling
  . running the new code on Android device gives a green screen video (duration 1 sec whatever the number of frames I encode)

  I saw another post about iPhone in a similar situation that mentioned the ARM processor optimization could be the culprit. I tried a few ldextra-flags (-arch armv7-a and similar) to no success.

  I include at the end the code that loads the image. Is there something different to do on Android than on linux ? Is my ffmpeg build not correct for Android video encoding ?

  void copyFrame(AVCodecContext *destContext, AVFrame* dest,
  
              AVCodecContext *srcContext, AVFrame* source) {
  
  struct SwsContext *swsContext;
  
  swsContext = sws_getContext(srcContext->width, srcContext->height, srcContext->pix_fmt,
  
                  destContext->width, destContext->height, destContext->pix_fmt,
  
                  SWS_FAST_BILINEAR, NULL, NULL, NULL);
  
  sws_scale(swsContext, source->data, source->linesize, 0, srcContext->height, dest->data, dest->linesize);
  
  sws_freeContext(swsContext);
  
  }
  
  
  
  int loadFromFile(const char* imageFileName, AVFrame* realPicture, AVCodecContext* videoContext) {
  
  AVFormatContext *pFormatCtx = NULL;
  
  avcodec_register_all();
  
  av_register_all();
  
  
  
  int ret = avformat_open_input(&pFormatCtx, imageFileName, NULL, NULL);
  
  if (ret != 0) {
  
      // ERROR hapening here
  
      // Can't open image file. Use strerror(AVERROR(ret))) for details
  
      return ERR_CANNOT_OPEN_IMAGE;
  
  }
  
  
  
  AVCodecContext *pCodecCtx;
  
  
  
  pCodecCtx = pFormatCtx->streams[0]->codec;
  
  pCodecCtx->width = W_VIDEO;
  
  pCodecCtx->height = H_VIDEO;
  
  pCodecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  
  
  // Find the decoder for the video stream
  
  AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
  
  if (!pCodec) {
  
      // Codec not found
  
      return ERR_CODEC_NOT_FOUND;
  
  }
  
  
  
  // Open codec
  
  if (avcodec_open(pCodecCtx, pCodec) < 0) {
  
      // Could not open codec
  
      return ERR_CANNOT_OPEN_CODEC;
  
  }
  
  
  
  // 
  
  AVFrame *pFrame;
  
  
  
  pFrame = avcodec_alloc_frame();
  
  
  
  if (!pFrame) {
  
      // Can't allocate memory for AVFrame
  
      return ERR_CANNOT_ALLOC_MEM;
  
  }
  
  
  
  int frameFinished;
  
  int numBytes;
  
  
  
  // Determine required buffer size and allocate buffer
  
  numBytes = avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
  
  uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof (uint8_t));
  
  
  
  avpicture_fill((AVPicture *) pFrame, buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
  
  AVPacket packet;
  
  int res = 0;
  
  while (av_read_frame(pFormatCtx, &packet) >= 0) {
  
      if (packet.stream_index != 0)
  
          continue;
  
  
  
      ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
      if (ret > 0) {
  
          // now, load the useful info into realPicture
  
          copyFrame(videoContext, realPicture, pCodecCtx, pFrame);
  
          // Free the packet that was allocated by av_read_frame
  
          av_free_packet(&packet);
  
          return 0;
  
      } else {
  
          // Error decoding frame. Use strerror(AVERROR(ret))) for details
  
          res = ERR_DECODE_FRAME;
  
      }
  
  }
  
  av_free(pFrame);
  
  
  
  // close codec
  
  avcodec_close(pCodecCtx);
  
  
  
  // Close the image file
  
  av_close_input_file(pFormatCtx);
  
  
  
  return res;
  
  }

  Some ./configure options :
  --extra-cflags="-O3 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 -Dipv6mr_interface=ipv6mr_ifindex -fasm -Wno-psabi -fno-short-enums -fno-strict-aliasing -finline-limit=300 -mfloat-abi=softfp -mfpu=vfp -marm -march=armv7-a -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE"

  --extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib -lc -lm -ldl -llog"

  --arch=armv7-a --enable-armv5te --enable-armv6 --enable-armvfp --enable-memalign-hack

• how to skip corrupted packets after av_read_frames()

  28 novembre 2015, par mrezvanee

  i am using FFmpeg functions to decode video content of a live mpeg2ts stream in VC++ ,sometimes there are access violation errors after using decoding functions (avcodec_decode_audio4/avcodec_decode_video2),it seems they are made by corrupted packets in low SNR condition.
  how can i skip corrupted packets from av_read_frames(AVFormatContexts AVPacket pkt) before using decoding functions like avcodec_decode_audio4 or avcodec_decode_video2 ???
  is there any flags in AVPacket structure to determine corrupted packets ???