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• Setting individual pixels of an RGB frame for ffmpeg encoding

  15 mai 2013, par Camille Goudeseune

  I'm trying to change the test pattern of an ffmpeg streamer, Trouble syncing libavformat/ffmpeg with x264 and RTP , into familiar RGB format. My broader goal is to compute frames of a streamed video on the fly.

  So I replaced its AV_PIX_FMT_MONOWHITE with AV_PIX_FMT_RGB24, which is "packed RGB 8:8:8, 24bpp, RGBRGB..." according to http://libav.org/doxygen/master/pixfmt_8h.html .

  To stuff its pixel array called data, I've tried many variations on

  for (int y=0; y/  const double j = y/double(HEIGHT);
  
      rgb[0] = 255*i;
  
      rgb[1] = 0;
  
      rgb[2] = 255*(1-i);
  
    }
  
  }

  At HEIGHTxWIDTH= 80x60, this version yields
  , when I expect a single blue-to-red horizontal gradient.

  640x480 yields the same 4-column pattern, but with far more horizontal stripes.

  640x640, 160x160, etc, yield three columns, cyan-ish / magenta-ish / yellow-ish, with the same kind of horizontal stripiness.

  Vertical gradients behave even more weirdly.

  Appearance was unaffected by an AV_PIX_FMT_RGBA attempt (4 not 3 bytes per pixel, alpha=255). Also unaffected by a port from C to C++.

  The argument srcStrides passed to sws_scale() is a length-1 array, containing the single int HEIGHT.

  Access each Pixel of AVFrame asks the same question in less detail, so far unanswered.

  The streamer emits one warning, which I doubt affects appearance :

  [rtp @ 0x269c0a0] Encoder did not produce proper pts, making some up.

  So. How do you set the RGB value of a pixel in a frame to be sent to sws_scale() (and then to x264_encoder_encode() and av_interleaved_write_frame()) ?

• How do I toggle individual codec options in libavcodec (specifically h264_options)

  2 juillet 2020, par John Allard

  I'm trying to figure out how to enable enable_er option as is defined in h264dec.c in libavcodec. This is defined as an AVOption as part of the AVCodec.priv_class.option field. I can't figure out if this is some sort of compile-time option or if it's an option that I can enable via the av_dict_set method when initializing an AVCodec via avcodec_open2.

  


  I'm talking about these options in h264dec.c

  


  #define OFFSET(x) offsetof(H264Context, x)
#define VD AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM
static const AVOption h264_options[] = {
    { "is_avc", "is avc", OFFSET(is_avc), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, 0 },
    { "nal_length_size", "nal_length_size", OFFSET(nal_length_size), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 4, 0 },
    { "enable_er", "Enable error resilience on damaged frames (unsafe)", OFFSET(enable_er), AV_OPT_TYPE_BOOL, { .i64 = -1 }, -1, 1, VD },
    { NULL },
};

static const AVClass h264_class = {
    .class_name = "H264 Decoder",
    .item_name  = av_default_item_name,
    .option     = h264_options,
    .version    = LIBAVUTIL_VERSION_INT,
};

AVCodec ff_h264_decoder = {
    .name                  = "h264",
    .long_name             = NULL_IF_CONFIG_SMALL("H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
    .type                  = AVMEDIA_TYPE_VIDEO,
    .id                    = AV_CODEC_ID_H264,
    .priv_data_size        = sizeof(H264Context),
    .init                  = h264_decode_init,
    .close                 = h264_decode_end,
    .decode                = h264_decode_frame,
    .capabilities          = /*AV_CODEC_CAP_DRAW_HORIZ_BAND |*/ AV_CODEC_CAP_DR1 |
                             AV_CODEC_CAP_DELAY | AV_CODEC_CAP_SLICE_THREADS |
                             AV_CODEC_CAP_FRAME_THREADS,
    .caps_internal         = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_EXPORTS_CROPPING,
    .flush                 = flush_dpb,
    .init_thread_copy      = ONLY_IF_THREADS_ENABLED(decode_init_thread_copy),
    .update_thread_context = ONLY_IF_THREADS_ENABLED(ff_h264_update_thread_context),
    .profiles              = NULL_IF_CONFIG_SMALL(ff_h264_profiles),
    .priv_class            = &h264_class,
};


  


• QuickTime plays separate audio tracks all at once with ffmpeg generated file

  23 mai 2022, par Justin Smith

  Let's say I have four files :

  


  

  • video.mp4

  


  • english.mp4

  


  • french.mp4

  


  • spanish.mp4

  


  


  I'm using the following ffmpeg command to create a single video file with multiple audio tracks for each language :

  


  ffmpeg -i video.mp4 -i english.mp4 -i spanish.mp4 -i french.mp4 \
-map 0:v -map 1:a -map 2:a -map 3:a \
-metadata:s:a:0 language=eng -metadata:s:a:0 title="English" \
-metadata:s:a:1 language=spa -metadata:s:a:1 title="Spanish" \
-metadata:s:a:2 language=fra -metadata:s:a:2 title="French" \
-disposition:a:0 default \
-c:v copy -c:a aac output.mp4


  


  The resulting video file output.mp4 works fine in VLC, but the audio tracks play all at once in QuickTime and the separate audio channels don't appear in the Languages menu. What am I doing wrong here ?