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• How to decode in ffmpeg using hardware (avcodec_parameters_to_context problem)

  25 juillet 2020, par Guerlando OCs

        AVCodecContext *ctx= NULL;
      AVCodecParameters *origin_par = NULL;


      result = avcodec_parameters_to_context(ctx, origin_par);
      if (result) {
          av_log(NULL, AV_LOG_ERROR, "Can't copy decoder context\n");
          return result;
      }


  


  where origin_par is filled by opening the file and reading some of its things :

  


     result = avformat_open_input(&fmt_ctx, input_filename, NULL, NULL);
   if (result < 0) {
       av_log(NULL, AV_LOG_ERROR, "Can't open file\n");
       return result;
   }

   result = avformat_find_stream_info(fmt_ctx, NULL);
   if (result < 0) {
       av_log(NULL, AV_LOG_ERROR, "Can't get stream info\n");
       return result;
   }

   video_stream = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
   if (video_stream < 0) {
     av_log(NULL, AV_LOG_ERROR, "Can't find video stream in input file\n");
     return -1;
   }

   origin_par = fmt_ctx->streams[video_stream]->codecpar;


  


  However, I don't have a file, I have an h264 stream. How do I make it work then ? I need a way to fill the parameters to the context using avcodec_parameters_to_context but without opening a file.

  


• sending udp cbr content using ffmpeg makes memory problem

  30 décembre 2020, par Przemo

  I am struggling with muxing a few UDP inputs (SPTS from file) in one UDP output (MPTS).
When I use following command

  


  ffmpeg -thread_queue_size 2048 -i "udp://233.0.0.1:4005?fifo_size=1000000&buffer_size=10000000" -thread_queue_size 2048 -i "udp://233.0.0.1:4000?fifo_size=1000000&buffer_size=10000000" -thread_queue_size 2048 -i "udp://233.0.0.1:4001?fifo_size=1000000&buffer_size=10000000" -thread_queue_size 2048 -i "udp://233.0.0.1:4002?fifo_size=1000000&buffer_size=10000000" -thread_queue_size 2048 -i "udp://233.0.0.1:4003?fifo_size=1000000&buffer_size=10000000" -thread_queue_size 2048 -i "udp://233.0.0.1:4004?fifo_size=1000000&buffer_size=10000000" -map 0 -map 1 -map 2 -map 3 -map 4 -map 5 -program title=Program0:st=0:st=1 -program title=Program1:st=2:st=3 -program title=Program2:st=4:st=5 -program title=Program3:st=6:st=7 -program title=Program4:st=8:st=9 -program title=Program5:st=10:st=11 -c copy -metadata service_provider=FILE -f mpegts -muxrate 40000000 -flush_packets 0 "udp://239.2.2.2:2222?overrun_nonfatal=1&fifo_size=1000000&buffer_size=10000000&pkt_size=1316&ttl=1"


  


  I can play (with VLC) the MPTS content many hours with no problems.

  


  When I add a bitrate parameter to make UDP output stream as CBR

  


  "udp://239.2.2.2:2222?overrun_nonfatal=1&fifo_size=1000000&buffer_size=10000000&pkt_size=1316&ttl=1&bitrate=40000000"


  


  instead of

  


  "udp://239.2.2.2:2222?overrun_nonfatal=1&fifo_size=1000000&buffer_size=10000000&pkt_size=1316&ttl=1"


  


  a hear many audio cuts, and from VLC I see then :

  


  


  main warning : timing screwed (drift : -89659 us) : stopping resampling
  
main warning : playback too early (-89367) : down-sampling
  
main warning : playback way too early (-126525) : playing silence
  
main debug : inserting 6073 zeroes
  
main warning : playback too early (-47858) : down-sampling
  
main warning : timing screwed (drift : -97495 us) : stopping resampling
  
main warning : playback too early (-96807) : down-sampling
  
main warning : playback way too early (-134672) : playing silence
  
main debug : inserting 6464 zeroes

  


  


  and after some random time (several minutes) ffmpeg stops working due to following error :

  


  


  av_interleaved_write_frame() : Cannot allocate memory

  


  


  How to make it work with CBR UDP bitrate ?
  
I tired changing parameters of buffer_size and fifo_size but with no success.
  
I've increased OS UDP buffers to improve performance but same memory problem is visible

  


• FFMPEG Webvtt m3u8 download into single vtt file, ignore the "X-TIMESTAMP-MAP=MPEGTS=" (timestamp sync problem)

  5 janvier 2021, par Panda Xia

  I want to download the subtitle of a video, it has separated m3u8 file for subtitle :

  


  webvtt source in m3u8 format : https://sdn-global-streaming-cache.3qsdn.com/9378/files/19/05/1199332/Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes.ism/Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes-textstream_deu=1000.m3u8

  


  looks like :

  


  #EXTM3U
#EXT-X-VERSION:4
## Created with Unified Streaming Platform(version=1.9.5)
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-MEDIA-SEQUENCE:1
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-TARGETDURATION:989
#USP-X-TIMESTAMP-MAP:MPEGTS=900000,LOCAL=1970-01-01T00:00:00Z
#EXTINF:24.72, no desc
Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes-textstream_deu=1000-1.webvtt
#EXTINF:2.56, no desc
Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes-textstream_deu=1000-13.webvtt
#EXTINF:50.88, no desc
Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes-textstream_deu=1000-14.webvtt
#EXTINF:3.079, no desc
Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes-textstream_deu=1000-40.webvtt
#EXTINF:60.401, no desc
....


  


  Then use the command to download the multiple webvtts into one vtt file "EN.vtt" :

  


  ffmpeg -i  "https://sdn-global-streaming-cache.3qsdn.com/9378/files/19/05/1199332/Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes.ism/Dqt6jZBkvX2nLyY4CGhxmpK89PbQRFV7-drm-aes-textstream_deu=1000.m3u8"  "DE.vtt"


  


  In output "DE.vtt" the X-TIMESTAMP-MAP=MPEGTS:xxxxxx,LOCAL:00:00:00.000 from each webvtt file (webvtt in m3u8) are ignored.

  


  so that the time Synchronisation is broken, the start time of each Segment always begins from 00:00:00, looks like :

  


  WEBVTT

00:00.000 --> 00:02.560
So viel Macht.

00:00.000 --> 00:03.079
Was er sagte.

00:00.000 --> 00:04.680
oder
die Schönheit

00:00.000 --> 00:01.440
Er sagte immer:

00:00.000 --> 00:03.840
Auf seinen Klang 

00:00.000 --> 00:07.519
Seine Paranoia.


  


  Could ffmpeg support the relative time stamp to convert into absolute time stamp ?
Or use other method to download perfect webvvt file ?