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• How to adjust mpeg 2 ts start time with ffmpeg ?

  29 juin 2015, par Maxim Kornienko

  I’m writing simple HLS (Http Live Streaming) java server to live cast (really live, not on demand) screenshow + voice. I constantly get chunks of image frames and audio samples as input to my service and produce mpeg 2 ts files + m3u8 playlist web page as output. The workflow is the following :

  1. Collect (buffer) source video frames and audio for certain period of time
  2. Convert series of video frames to h.264 encoded video file
  3. Convert audio samples to mp3 audio file

  4. Merge them to .ts file with ffmpeg command

     ffmpeg -i audio.mp3 -i video.mp4 -f mpegts -c:a copy -c:v copy -vprofile main -level:v 4.0 -vbsf h264_mp4toannexb -flags -global_header segment.ts

  5. Publish several .ts files on m3u8 playlist.

  The problem is resulting playlist interrupts after first segment is played. VLC logs following error :

  freetype error: Breaking unbreakable line
  
  ts error: libdvbpsi (PSI decoder): TS discontinuity (received 0, expected 4) for PID 17
  
  ts error: libdvbpsi (PSI decoder): TS duplicate (received 0, expected 1) for PID 0
  
  ts error: libdvbpsi (PSI decoder): TS duplicate (received 0, expected 1) for PID 4096
  
  core error: ES_OUT_SET_(GROUP_)PCR is called too late (pts_delay increased to 1000 ms)
  
  core error: ES_OUT_RESET_PCR called
  
  core error: Could not convert timestamp 185529572000
  
  ts error: libdvbpsi (PSI decoder): TS discontinuity (received 0, expected 4) for PID 17
  
  ts error: libdvbpsi (PSI decoder): TS duplicate (received 0, expected 1) for PID 0
  
  ts error: libdvbpsi (PSI decoder): TS duplicate (received 0, expected 1) for PID 4096
  
  core error: ES_OUT_SET_(GROUP_)PCR is called too late (jitter of 8653 ms ignored)
  
  core error: Could not get display date for timestamp 0
  
  core error: Could not convert timestamp 185538017000
  
  core error: Could not convert timestamp 185538267000
  
  core error: Could not convert timestamp 185539295977
  
  ...

  I guess the reason is that start time of segments do not belong to one stream, but it’s impossible to concat and resegment (with ffmepg -f segment) whole stream once new chunk is added. Tried adding #EXT-X-DISCONTINUITY tag to playlist as suggested here but it didn’t help. When I ffprobe them I get :

  Input #0, mpegts, from '26.ts':
  
  Duration: 00:00:10.02, start: 1.876978, bitrate: 105 kb/s
  
  Program 1
  
  Metadata:
  
    service_name    : Service01
  
    service_provider: FFmpeg
  
  Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 640x640, 4 fps, 4 tbr, 90k tbn, 8 tbc
  
  Stream #0:1[0x101]: Audio: mp3 ([3][0][0][0] / 0x0003), 48000 Hz, mono, s16p, 64 kb/s   

  Where start value in line Duration: 00:00:10.02, start: 1.876978, bitrate: 105 kb/s is more or less equal for all segments.
  When I check segments from available proven-to-work playlists (like http://vevoplaylist-live.hls.adaptive.level3.net/vevo/ch1/appleman.m3u8) they all have diffrenet start values for each segment, for example :

  Input #0, mpegts, from 'segm150518140104572-424570.ts':
  
  Duration: 00:00:06.17, start: 65884.808689, bitrate: 479 kb/s
  
  Program 257
  
  Stream #0:0[0x20]: Video: h264 (Constrained Baseline) ([27][0][0][0] / 0x001B), yuv420p, 320x180 [SAR 1:1 DAR 16:9], 30 fps, 29.97 tbr, 90k tbn, 60 tbc
  
  Stream #0:1[0x21]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 115 kb/s
  
  Stream #0:2[0x22]: Data: timed_id3 (ID3  / 0x20334449)

  and the next after it

  Input #0, mpegts, from 'segm150518140104572-424571.ts':
  
  Duration: 00:00:06.22, start: 65890.814689, bitrate: 468 kb/s
  
  Program 257
  
  Stream #0:0[0x20]: Video: h264 (Constrained Baseline) ([27][0][0][0] / 0x001B), yuv420p, 320x180 [SAR 1:1 DAR 16:9], 30 fps, 29.97 tbr, 90k tbn, 60 tbc
  
  Stream #0:1[0x21]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 124 kb/s
  
  Stream #0:2[0x22]: Data: timed_id3 (ID3  / 0x20334449)

  differ in the way that start time of segm150518140104572-424571.ts is equal to start time + duration of segm150518140104572-424570.ts.

  How could this start value be adjusted with ffmpeg ? Or maybe my whole aproach is wrong ? Unfortunately I couldn’t find on the internet working example of live (not on demand) video service implemented with ffmepg.

• subprocess Task fail after 8min when run inside Flask or BaseHTTPServer

  6 août 2015, par jthemovie

  I’m doing live HLS encoding with ffmpeg, and i usually run it via a python program as follow (i made some shortcuts...) :

  import subprocess
  
  
  
  def main():
  
      subprocess.Popen("ffmpeg -i .... (live hls encoding)", shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  if __name__ == '__main__':
  
     main()

  And everything works like a charm, but when i use Flask or BaseHTTPServer, the very same weird behaviour occurs.

  After around 8min (more or less few seconds), the program stop responding and the encoding stop.

  import subprocess
  
  from flask import Flask, url_for, request, json, Response
  
  
  
  @app.route('/api/v2/livetv', methods = ['POST'])
  
  def api_live():
  
      subprocess.Popen("ffmpeg -i .... (live hls encoding)", shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
      return "-"
  
  
  
  if __name__ == '__main__':
  
     app.run(host='127.0.0.1', port=5001,debug=True)

  I tried using BaseHTTPServer, the very same behaviour occurs, it usually stop encoding after the segment number 46, or 47, which correspond at those 8 min.

  I have no idea why this behavior occurs. For example, the first script, once terminated, the ffmpeg will continue in background, while if i terminate the script with the web server, the ffmpeg program will exit as well.

  So if anyone could help me out with that, i would be more than glad.

  Thanks a lot for your help.

  Regards

  ps : if interested , my ffmpeg line look like this :

  /usr/bin/ffmpeg -user-agent "A User Agent" -headers "X-Forwarded-For:x.x.x.x"$’\r\n’ -re -i "http://..../index_2000_av-p.m3u8" -c:v libx264 -profile:v baseline -preset medium -x264opts level=41 -b:v 500k -s 600x340 -g 90 -bf 2 -c:a copy -f hls -hls_list_size 20 -hls_time 10 -hls_flags delete_segments -hls_segment_filename /var/www/livestream/"segment%03d.ts" /var/www/livestream/playlist.m3u8

• ffmpeg generate m3u8 and segments manually

  26 juin 2015, par Darshan Bhandari

  We are developing an application where the m3u8 file should be generated on the fly for a given mp4 video. Can someone please let us know how can we generate the mp4 file on the fly with the exact duration as the segmenter. In our case ffmpeg segmenter is created variable length segments and are of decimal size. For eg :
  #EXTM3U
  #EXT-X-VERSION:3
  #EXT-X-TARGETDURATION:7
  #EXT-X-PLAYLIST-TYPE:VOD

  #EXTINF:5.005,
  
  test.mp4.ts?start=0.000&end=5.005
  
  #EXTINF:6.715,
  
  test.mp4.ts?start=5.005&end=11.720
  
  #EXTINF:6.548,

  Can someone help us to create such m3u8 file without creating any segments. We will manually create the segments on request.

  Also when we create the segments manually there is a small stuttering (flicker) when the video goes to the next segment. When I read it online, it says it might be due to continuity counter. Can someone please help us fix that too

  Thanks.