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• FFmpeg : avcodec_encode_video() and JPEG images

  2 février 2012, par user105909

  I'm trying to encode a series of .jpg files into a video using the ffmpeg library, and I can't seem to get the frames to encode. (I have to use the ffmpeg library, and using ffmpeg from a command line is not an option in my case.)

  Except for the part where I'm trying to open JPG files as AVFrames, my code is more or less the same thing as found in api-example.c from the ffmpeg library. When I populate the frames as the example does, everything works as expected. In the code below, I fail to encode any frames. Obviously the trouble is related to how I'm opening the JPG files, but I can't figure out what.

  I'm opening the image like this :

  AVFrame* open_image(const char* imageFileName, int width, int height, long * bufSize)
  
  {
  
      AVFormatContext *pFormatCtx;
  
  
  
      if(av_open_input_file(&pFormatCtx, imageFileName, NULL, 0, NULL)!=0)
  
      {
  
          printf("Can't open image file '%s'\n", imageFileName);
  
          return NULL;
  
      }       
  
  
  
      AVCodecContext *pCodecCtx;
  
  
  
      pCodecCtx = pFormatCtx->streams[0]->codec;
  
      pCodecCtx->width = width;
  
      pCodecCtx->height = height;
  
      pCodecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  
  
      // Find the decoder for the video stream
  
      AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
  
      if (!pCodec)
  
      {
  
          printf("Codec not found\n");
  
          return NULL;
  
      }
  
  
  
      // Open codec
  
      if(avcodec_open(pCodecCtx, pCodec)<0)
  
      {
  
          printf("Could not open codec\n");
  
          return NULL;
  
      }
  
  
  
      AVFrame *pFrame = avcodec_alloc_frame();
  
      if (!pFrame)
  
      {
  
          LOGV(TAG, "Can't allocate memory for AVFrame\n");
  
          return NULL;
  
      }
  
  
  
      int frameFinished;
  
      int numBytes;
  
  
  
      // Determine required buffer size and allocate buffer
  
      numBytes = avpicture_get_size(PIX_FMT_YUVJ420P, pCodecCtx->width, pCodecCtx->height);
  
  
  
      // ***
  
      *bufSize = numBytes;
  
      // ***
  
  
  
      uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
  
  
  
      avpicture_fill((AVPicture *) pFrame, buffer, PIX_FMT_YUVJ420P, pCodecCtx->width, pCodecCtx->height);
  
  
  
      // Read frame
  
  
  
      AVPacket packet;
  
  
  
      int framesNumber = 0;
  
      while (av_read_frame(pFormatCtx, &packet) >= 0)
  
      {
  
          if(packet.stream_index != 0)
  
              continue;
  
  
  
          int ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
          if (ret > 0)
  
          {
  
              sprintf(buf, "Frame is decoded, size %d", ret);
  
              LOGV(TAG, buf);
  
              pFrame->quality = 4;
  
              return pFrame;
  
          }
  
          else {
  
              // printf("Error [%d] while decoding frame: %s\n", ret, strerror(AVERROR(ret)));
  
              sprintf(buf, "Error %d decoding frame: %s", ret, strerror(AVERROR(ret)));
  
              LOGV(TAG, buf);
  
          }
  
      }
  
  }

  ...and attempting to encode them like this :

  DIR * dir = opendir(path);
  
  int i = 0;
  
  
  
  if (dir != NULL) {
  
  
  
      for(struct dirent *ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  
          fflush(stdout);
  
  
  
          printf("%s/%s", path, ent->d_name);
  
          LOGV(TAG, filename);
  
  
  
          // If not a jpg file, pass it over
  
          const char * ext = strrchr(filename, '.');
  
          if((!ext) || (strcmp(ext, ".jpg"))) {
  
              continue;
  
          }
  
  
  
          /*** NOTE: Is this where I've gone wrong? Bufsize is set in open_image based on av_picture_size() */
  
          long bufSize = 0L;
  
          AVFrame * frame = open_image(filename, width, height, &bufSize);
  
          if(frame) {
  
              // This is what it needs to do, and it does not work.
  
              // Causes:
  
              // Wrong format?
  
              // Wrong buffer size?
  
              uint8_t * picBuf = (uint8_t *)malloc(bufSize);
  
  
  
              out_size = avcodec_encode_video(c, picBuf, bufSize, frame);
  
  
  
              printf("encoding frame %3d (size=%5d)\n", i++, out_size);
  
              /** On the first image, out_size is 0. On the next, it's -1, and fails. */
  
  
  
              if(out_size < 0) {
  
                  printf("Error encoding frame");
  
                  return -6;
  
              }
  
  
  
              fwrite(picBuf, 1, bufSize, f);
  
  
  
              free(picBuf);
  
              av_free(frame);
  
          }
  
          else {
  
              printf("Couldn't open image");
  
              return -5;
  
          }
  
      }
  
  
  
      closedir(dir);
  
  } 
  
  else {
  
      printf("Couldn't open directory %s\n", path);
  
      return -4;
  
  }

  Could someone point me in the right direction ?

• Change file format from flv to anything android will play

  19 octobre 2011, par Bilthon

  I need to take this file which encoded is in h264 but in a flv container and just put it in a mp4, 3gp or whatever file format the android MediaPlayer will understand.

  I want to do this natively. As I will not be decoding nor encoding anything I think I will not be wasting a lot of power (am I wrong ?)

  I followed the instructions from here http://www.roman10.net/?p=394 and could sucessfully compile and use ffmpeg and use it with mp4 and 3gp files.

  But when it comes to flv files it fails. I understand there is no format definition for flv files in that specific port of ffmpeg for android.

  There is no libavformat/flv.h header file for instance.

  Maybe that's why this works :

  extern AVInputFormat ff_mov_demuxer ;
  av_register_input_format(&ff_mov_demuxer) ;

  While this fails :

  extern AVInputFormat ff_flv_demuxer;
  
  av_register_input_format(&ff_flv_demuxer);

  Question is, is there a light at the end of the tunnel ? has someone done something similar ? is it useful ? I mean, I can always just throw the flv media file into a flash player and voila.. the thing is that this would be a parcial solution, as it will not work for all those folks running slower devices that can't yet run Flash.

  Nelson

  PS. Just in case. Here's some info about the file I'm talking about :

  ffmpeg -i rio.flv 
  
  ffmpeg version N-32624-gea8de10, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Sep 15 2011 23:31:42 with gcc 4.5.2
  
    configuration: --enable-libfaac --enable-libmp3lame --enable-librtmp --enable-libtheora --enable-libx264 --enable-libxvid --enable-gpl --enable-nonfree
  
    libavutil    51. 16. 0 / 51. 16. 0
  
    libavcodec   53. 15. 0 / 53. 15. 0
  
    libavformat  53. 12. 0 / 53. 12. 0
  
    libavdevice  53.  3. 0 / 53.  3. 0
  
    libavfilter   2. 42. 0 /  2. 42. 0
  
    libswscale    2.  1. 0 /  2.  1. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  
  
  Seems stream 0 codec frame rate differs from container frame rate: 2000.00 (2000/1) -> 14.99 (15000/1001)
  
  Input #0, flv, from 'rio.flv':
  
    Duration: 00:01:00.06, start: 0.000000, bitrate: 783 kb/s
  
      Stream #0.0: Video: h264 (Main), yuv420p, 704x480 [SAR 10:11 DAR 4:3], 14.99 tbr, 1k tbn, 2k tbc

• Is using QtFFmpegWrapper+QLabel+QTimer a good way to play video in a Qt application ?

  21 décembre 2012, par Vi.

  I'm looking how to portably play video on Qt, but not Phonon.

  Using ffmpeg seems to be a good idea (it should work the same way on all platforms).

  Currently It uses QLabel for video output and does QPixmap::fromImage for each frame ; frames which are decoded and buffered by QtFFmpegWrapper in a background thread. QTimer decides when to show the next frame.

  The whole thing looks a bit hacky (Video ? In a label ?). Am I doing it right ? Is there a better portable way of playing ffmpeg-decoded video in a Qt application ?