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• Synchronize raspicam video and arecord for ffmpeg rtmp streaming

  6 mars 2017, par Роман Мальцев

  I’m trying to synchronize video and audio from my raspicam and arecord and make rtmp stream with ffmpeg and 3g modem, but don’t know how to do that. I have tried with this code :

  raspivid -t 0 -w 1024 -h 768 -fps 25 -vf -hf -b 1000000 -v -o temp.v & arecord -f cd -D plughw:0 | ffmpeg -i temp.v -itsoffset 13.5 -i - -c:v copy -c:a libmp3lame -b:a 64k -vsync 0 -f flv rtmp://ipofmynginxserver/myapp/mystream

  and

  raspivid -t 0 -w 1024 -h 768 -fps 25 -g 60 -vf -hf -b 1000000 -v -o temp.v & arecord -f cd -D plughw:0 | ffmpeg -r 25.37 -i temp.v -itsoffset 13.5 -i - -c:v copy -c:a libmp3lame -b:a 64k -vsync 0 -async 1 -f flv rtmp://ipofmynginxserver/myapp/mystream

  At first everything is fine (because of the offset) But after connection lost for 2-4 seconds audio and video starting to play asynchronus (audio first)
  I have tried to change options vsync and async but it didn’t make sense. If I’m trying to get alsa microphone with ffmpeg I’m getting alsa buffer xrun and it doesn’t work, the only way for me is to use raspivid and arecord, how can I solve my problem ? Thanks and sorry for my English.

• ffmpeg how to convert pgs subtitles to srt

  20 mai 2015, par 8ofspades

  I’m having an issue with extracting subtitles from ffmpeg 2.6.2. I have an mkv file with 6 subtitle streams, and I would like to generate srt files for all of them. My ffprobe output for the streams is below.

      Stream #0:0(eng): Video: h264 (High), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 29.97 fps, 29.97 tbr, 1k tbn, 59.94 tbc (default)
  
  Stream #0:1(ita): Audio: ac3, 48000 Hz, stereo, fltp, 448 kb/s (default)
  
  Stream #0:2(ita): Audio: dts (DTS), 48000 Hz, 5.0(side), fltp, 1536 kb/s
  
  Metadata:
  
    title           : Italian
  
  Stream #0:3(rus): Subtitle: subrip (default)
  
  Metadata:
  
    title           : Russian
  
  Stream #0:4(ita): Subtitle: hdmv_pgs_subtitle
  
  Metadata:
  
    title           : Italian
  
  Stream #0:5(eng): Subtitle: hdmv_pgs_subtitle
  
  Metadata:
  
    title           : English
  
  Stream #0:6(fre): Subtitle: hdmv_pgs_subtitle
  
  Metadata:
  
    title           : French
  
  Stream #0:7(ger): Subtitle: hdmv_pgs_subtitle
  
  Metadata:
  
    title           : German
  
  Stream #0:8(spa): Subtitle: hdmv_pgs_subtitle
  
  Metadata:
  
    title           : Spanish

  The russian (subrip) subtitles work fine with

  ffmpeg -i input.mkv -c:s:0 copy sub_ru.srt

  however when I try and select and of the other (pgs) subtitle streams, it ignores the stream I selected and outputs the russian (stream 0:3) subtitles.

  I’m not sure if this an issue with my ffmpeg command or the fact that the other streams are pgs.

  Thanks

• Python : mp3 to wave.open(f,'r') through ffmpeg pipe

  7 avril 2015, par user2754098

  I’m trying to decode mp3 to wav using ffmpeg :

  import alsaaudio
  
  import wave
  
  from subprocess import Popen, PIPE
  
  
  
  with open('filename.mp3', 'rb') as infile:
  
      p=Popen(['ffmpeg', '-i', '-', '-f', 'wav', '-'], stdin=infile, stdout=PIPE)
  
      ...

  Next i want redirect data from p.stdout.read() to wave.open(file, r) to use readframes(n) and other methods. But i cannot because ’file’ in wave.open(file,’r’) can be only name of file or an open file pointer.

      ...
  
      file = wave.open(p.stdout.read(),'r')
  
      card='default'
  
      device=alsaaudio.PCM(card=card)
  
      device.setchannels(file.getnchannels())
  
      device.setrate(file.getframerate())
  
      device.setformat(alsaaudio.PCM_FORMAT_S16_LE)
  
      device.setsetperiodsize(320)
  
      data = file.readframes(320)
  
      while data:
  
          device.write(data)
  
          data = file.readframes(320)

  I got :

  TypeError: file() argument 1 must be encoded string without NULL bytes, not str

  So is it possible to handle data from p.stdout.read() by wave.open() ?
  Making temporary .wav file isn’t solution.

  Sorry for my english.
  Thanks.