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• ffmpeg : record 1 hour segment, right on the hour, no/little frame lost [closed]

  2 septembre 2024, par Jean-Michel

  I need to record 24/7 an incoming SRT stream into 1 hour chunks, starting right on the hour.
The start needs to be as close as XX:00:00.000 as possible and little to no frame lost between the recordings.

  


  For now I am using a systemd service with that ExecStart command :

  


  /usr/bin/ffmpeg -fflags +discardcorrupt -i 'srt://:4010?pkt_size=1316&mode=listener' -c copy -map 0:v:0 -map 0:a? -f segment -strftime 1 -segment_time 3600 -reset_timestamps 1 -segment_format ts '/somefolder/recording_%%d%%m%%Y_%%H%%M00.ts'


  


  And using a crontab to restart the service on the hour to insure the next file properly starts at the expected time.

  


  0 * * * * cd /etc/systemd/system && systemctl restart srt_recorder_4010.service


  


  Unfortunately, the restart of the service takes 5 to 10 seconds and we are loosing that duration in the recorded file.
If I'm not using the crontab, I get 1 hour files but I have no control on the start time.

  


  Any suggestion to get something more accurate ?
Could there be a way to combine ffmpeg internal ability to exactly segment 1 hour file but enforce to do it on the hour ?
Or externally, if there was a way to send a "next file" command (api, signal) to a perpetual running ffmpeg to change recording file ?

  


  Thanks

  


• 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,
};


  


• 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()) ?