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• ffmpeg in "streaming mode" suddenly stops writing output file and resumes after several minutes

  29 juin 2018, par EliA

  I’m using ffmpeg to convert chunks of media in webm format to a wav file in a "continuous stream" mode.

  Using a python wrapper, I’m feeding ffmpeg a webm chunk (let’s say 1 chunk each second) and ffmpeg continuously writes the output wav (then, in a separate thread I’m reading this wav file and pass the new data forward).

  This works well most of the time, but some times, I get this weird behavior :

  • after some chunks are processed and output to the wav file, ffmpeg stops writing to the output file (the file stops growing but ffmpeg keeps getting the webm chunks)
  • this can go on like this for several minutes, and then ffmpeg resumes writing to the wav file
  • eventually, the complete wav file is written successfully, but this causes huge delays in the streaming process.

  Looking at CPU and memory usage, this doesn’t seem to be the issue.

  Any ideas as to what could cause ffmpeg to stop streaming for several minutes and then resume ?
  This can happen after 30 seconds, after 3 minutes or after an hour of streaming media chunks and the time it takes ffmpeg to resume also varies.

  In my python code, I’m basically opening a subprocess.Popen() process and write to the process’ stdin to feed ffmpeg the media chunks.

  So my code looks something like :

  ffmpeg_proc = subprocess.Popen('ffmpeg -y -f webm -i - -ac 1 -ar 16000  -f wav /tmp/out.wav', shell=True, stdin=subprocess.PIPE)
  
  
  
  for chunk in chunks:
  
      ffmpeg_proc.stdin.write(chunk)

  I’m using python 3.6 and ffmpeg version 2.8.14-0ubuntu0.16.04.1

  Thanks in advance !

• Unable to find a suitable output format for "-i ... "

  29 juin 2018, par Pan Ng

  I am using writemind’s ffmpeg module (running ffmpeg v3.0.2)
  http://writingminds.github.io/ffmpeg-android-java/

  But I am getting the follow error when executing the command

  [NULL @ 0xe93aa000] Unable to find a suitable output format for ’ -i
  "/storage/emulated/0/Android/data/com.charaku.popsical.tv/cache/video_recording.mp4"
  -i "/storage/emulated/0/Download/132859_aac-group-2.mp4" -c:v copy -filter_complex ’[1:a] adelay=2500|2500 [delayed] ; [0:a] [delayed] amix [out]’ -map 0:v -map ’[out]’
  "/storage/emulated/0/Android/data/com.charaku.popsical.tv/cache/mixed_test2.mp4"’
  -i "/storage/emulated/0/Android/data/com.charaku.popsical.tv/cache/video_recording.mp4"
  -i "/storage/emulated/0/Download/132859_aac-group-2.mp4" -c:v copy -filter_complex ’[1:a] adelay=2500|2500 [delayed] ; [0:a] [delayed] amix [out]’ -map 0:v -map ’[out]’
  "/storage/emulated/0/Android/data/com.charaku.popsical.tv/cache/mixed_test2.mp4" :
  Invalid argument

  The command is supposed to mix the audio of a video file with the audio of another audio file to produce a new video file.

• avcodec/aac_ac3_parser : account for data already in the parsing buffer

  5 avril 2018, par Hendrik Leppkes

  avcodec/aac_ac3_parser : account for data already in the parsing buffer
  If a frame starts very close to a packet boundary, the start code may
  
  already have been added to the parsing buffer, indicated by a small
  
  negative value of "i", while the header is still being tracked in the
  
  "state" variable.
  Reduce the remaining size accordingly, otherwise trying to find the next
  
  frame could skip over the frame header and lump two frames together as
  
  one.
  

  • [DH] libavcodec/aac_ac3_parser.c