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• what is wrong with this ffmpeg command ?

  16 juillet 2013, par kheya

  I am trying to convert 3gp movie to H264 video (mp4)
  This is what I am using :

  ffmpeg -i file8.3gp -vcodec libx264 -preset slow -vf scale="720:trunc(ow/a/2)*2" -threads 0 -acodec libvo_aacenc -b:a 128k "file8.mp4"

  The problem is original file is 28kb but after conversion I get 155kb mp4 file
  Why is the file so bloated - is that because of the size or some other option ?

  Here is what I see on 3gp input file : NOTE THE BIT RATE IS 46 KB/S

  libavutil      52. 39.100 / 52. 39.100
  
    libavcodec     55. 18.102 / 55. 18.102
  
    libavformat    55. 12.102 / 55. 12.102
  
    libavdevice    55.  3.100 / 55.  3.100
  
    libavfilter     3. 80.101 /  3. 80.101
  
    libswscale      2.  3.100 /  2.  3.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'file8.3gp':
  
    Metadata:
  
      major_brand     : 3gp5
  
      minor_version   : 256
  
      compatible_brands: 3gp53gp4
  
      creation_time   : 2005-10-28 17:36:40
  
    Duration: 00:00:04.93, start: 0.000000, bitrate: 46 kb/s
  
      Stream #0:0(eng): Audio: amr_nb (samr / 0x726D6173), 8000 Hz, mono, flt, 8 k
  
  b/s
  
      Metadata:
  
        creation_time   : 2005-10-28 17:36:40
  
        handler_name    : Apple Sound Media Handler
  
      Stream #0:1(eng): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p
  
  , 176x144 [SAR 1:1 DAR 11:9], 35 kb/s, 15 fps, 15 tbr, 600 tbn, 1k tbc
  
      Metadata:
  
        creation_time   : 2005-10-28 17:36:40
  
        handler_name    : Apple Video Media Handler

  Here is what I see on mp4 output file : NOTE THE BIT RATE IS 243 KB/S

  libavutil      52. 39.100 / 52. 39.100
  
    libavcodec     55. 18.102 / 55. 18.102
  
    libavformat    55. 12.102 / 55. 12.102
  
    libavdevice    55.  3.100 / 55.  3.100
  
    libavfilter     3. 80.101 /  3. 80.101
  
    libswscale      2.  3.100 /  2.  3.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'file8.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf55.12.102
  
    Duration: 00:00:05.20, start: 0.200000, bitrate: 243 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 720x588 [
  
  SAR 539:540 DAR 11:9], 240 kb/s, 15 fps, 15 tbr, 15360 tbn, 30 tbc
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 8000 Hz, mono, fltp, 10 kb
  
  /s
  
      Metadata:
  
        handler_name    : SoundHandler
  
  At least one output file must be specified

• Generated ffmpeg video from images has the wrong orientation

  14 septembre 2020, par asored

  I create a video from image files in Flutter (with ffmpeg) with this code :

  


  -r $settings_fps -i $tempPath/img%04d.jpg -vcodec libx264 -y -an -vf "pad=ceil(iw/2)*2:ceil(ih/2)*2" -pix_fmt yuv420p $tempPath/$videoFileName.mp4

  


  Then I add audio to the video file :

  


  -i ${finalSong.path} -i $videoPath -c:v copy -c:a aac -shortest $tempPath/$newVideoFileName.mp4

  


  It is possible that ffmpeg uses the AspectRatio of the first image ? And that ffmpeg detects automatically if it has a landscape or a portrait orientation ?

  


  Actually if I have images made in portrait orientation this is the video output :

  


  

  


  I know that I can rotate the video. But users have the possibility to add images in Portrait or Landscape orientation..so I don´t want manually rotate this video.

  


  Do you have another solution for this ? Thank you !

  


• What's wrong with my use of timestamps/timebases for frame seeking/reading using libav (ffmpeg) ?

  17 septembre 2013, par mtree

  So I want to grab a frame from a video at a specific time using libav for the use as a thumbnail.

  What I'm using is the following code. It compiles and works fine (in regards to retrieving a picture at all), yet I'm having a hard time getting it to retrieve the right picture.

  I simply can't get my head around the all but clear logic behind libav's apparent use of multiple time-bases per video. Specifically figuring out which functions expect/return which type of time-base.

  The docs were of basically no help whatsoever, unfortunately. SO to the rescue ?

  #define ABORT(x) do {fprintf(stderr, x); exit(1);} while(0)
  
  
  
  av_register_all();
  
  
  
  AVFormatContext *format_context = ...;
  
  AVCodec *codec = ...;
  
  AVStream *stream = ...;
  
  AVCodecContext *codec_context = ...;
  
  int stream_index = ...;
  
  
  
  // open codec_context, etc.
  
  
  
  AVRational stream_time_base = stream->time_base;
  
  AVRational codec_time_base = codec_context->time_base;
  
  
  
  printf("stream_time_base: %d / %d = %.5f\n", stream_time_base.num, stream_time_base.den, av_q2d(stream_time_base));
  
  printf("codec_time_base: %d / %d = %.5f\n\n", codec_time_base.num, codec_time_base.den, av_q2d(codec_time_base));
  
  
  
  AVFrame *frame = avcodec_alloc_frame();
  
  
  
  printf("duration: %lld @ %d/sec (%.2f sec)\n", format_context->duration, AV_TIME_BASE, (double)format_context->duration / AV_TIME_BASE);
  
  printf("duration: %lld @ %d/sec (stream time base)\n\n", format_context->duration / AV_TIME_BASE * stream_time_base.den, stream_time_base.den);
  
  printf("duration: %lld @ %d/sec (codec time base)\n", format_context->duration / AV_TIME_BASE * codec_time_base.den, codec_time_base.den);
  
  
  
  double request_time = 10.0; // 10 seconds. Video's total duration is ~20sec
  
  int64_t request_timestamp = request_time / av_q2d(stream_time_base);
  
  printf("requested: %.2f (sec)\t-> %2lld (pts)\n", request_time, request_timestamp);
  
  
  
  av_seek_frame(format_context, stream_index, request_timestamp, 0);
  
  
  
  AVPacket packet;
  
  int frame_finished;
  
  do {
  
      if (av_read_frame(format_context, &packet) < 0) {
  
          break;
  
      } else if (packet.stream_index != stream_index) {
  
          av_free_packet(&packet);
  
          continue;
  
      }
  
      avcodec_decode_video2(codec_context, frame, &frame_finished, &packet);
  
  } while (!frame_finished);
  
  
  
  // do something with frame
  
  
  
  int64_t received_timestamp = frame->pkt_pts;
  
  double received_time = received_timestamp * av_q2d(stream_time_base);
  
  printf("received:  %.2f (sec)\t-> %2lld (pts)\n\n", received_time, received_timestamp);

  Running this with a test movie file I get this output :

      stream_time_base: 1 / 30000 = 0.00003
  
      codec_time_base: 50 / 2997 = 0.01668
  
  
  
      duration: 20062041 @ 1000000/sec (20.06 sec)
  
      duration: 600000 @ 30000/sec (stream time base)
  
      duration: 59940 @ 2997/sec (codec time base)
  
  
  
      requested: 10.00 (sec)  -> 300000 (pts)
  
      received:  0.07 (sec)   -> 2002 (pts)

  The times don't match. What's going on here ? What am I doing wrong ?

  ---

  While searching for clues I stumbled upon this this statement from the libav-users mailing list…

  [...] packet PTS/DTS are in units of the format context's time_base,
  where the AVFrame->pts value is in units of the codec context's time_base.

  In other words, the container can have (and usually does) a different
  time_base than the codec. Most libav players don't bother using the
  codec's time_base or pts since not all codecs have one, but most
  containers do. (This is why the dranger tutorial says to ignore AVFrame->pts)

  …which confused me even more, given that I couldn't find any such mention in the official docs.

  Anyway, I replaced…

  double received_time = received_timestamp * av_q2d(stream_time_base);

  …with…

  double received_time = received_timestamp * av_q2d(codec_time_base);

  …and the output changed to this…

  ...
  
  
  
  requested: 10.00 (sec)  -> 300000 (pts)
  
  received:  33.40 (sec)  -> 2002 (pts)

  Still no match. What's wrong ?