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• Recover corrupted mp4 from an app

  9 janvier 2018, par user924

  We can easily fix corrupted mp4 file (for example if we were recording video, but it wasn’t stopped correctly) on Windows using next method

  REM 1) any good mp4 file with the same resolution and bitrate to generate the header files:
  
  
  
  recover_mp4.exe good.mp4 --analyze
  
  
  
  REM 2) recover streams from the corrupted file, for example:
  
  
  
  recover_mp4.exe bad.mp4 recovered.h264 recovered.aac
  
  
  
  REM 3) join audio and video with ffmpeg:
  
  
  
  ffmpeg.exe -r 30 -i recovered.h264 -i recovered.aac -bsf:a aac_adtstoasc -c:v copy -c:a copy recovered.mp4
  
  
  
  REM delete temp files:
  
  
  
  del *.h264
  
  del *.aac
  
  del *.hdr

  So we need some similar good (not corrupted) mp4 file and next tools :

  • recover_mp4 : http://slydiman.me/eng/mmedia/recover_mp4.htm
  • FFmpeg : https://www.ffmpeg.org/

  Is it possible to implement something similar in Android application ?
  I know there is ffmpeg library available for android (https://github.com/WritingMinds/ffmpeg-android-java), it works ok

  But unfortunately recover_mp4 isn’t available for android

  Mb there is already similar recover tool available for android ?

• Real time audio streaming from ffmpeg to browser (am I missing something ?)

  19 septembre 2022, par Яктенс Тид

  I have tried a couple of solutions already, but nothing works for me.
I want to stream audio from my PC to another computer with almost zero latency. Things are working fine so far in a sense of lagging and everything, sound is clear and not choppy at all, but there is something like a delay between the moment when audio starts playing on my PC and remote PC. For example when I click on Youtube 'play' button audio starts playing only after 3-4 seconds on the remote machine. The same when I click 'Pause', the sound on the remote PC stops after a couple of seconds.

  


  I've tried to use websockets\plain audio tag, but no luck so far.

  


  For example this is my solution by using websockets and pipes :

  


  def create_pipe():
    return win32pipe.CreateNamedPipe(r'\\.\pipe\__audio_ffmpeg', win32pipe.PIPE_ACCESS_INBOUND,
                                     win32pipe.PIPE_TYPE_MESSAGE |
                                     win32pipe.PIPE_READMODE_MESSAGE |
                                     win32pipe.PIPE_WAIT, 1, 1024 * 8, 1024 * 8, 0, None)


async def echo(websocket):
    pipe = create_pipe()
    win32pipe.ConnectNamedPipe(pipe, None)
    while True:
        data = win32file.ReadFile(pipe, 1024 * 2)
        await websocket.send(data[1])


async def main():
    async with websockets.serve(echo, "0.0.0.0", 7777):
        await asyncio.Future()  # run forever


if __name__ == '__main__':
    asyncio.run(main())


  


  The way I start ffmpeg

  


  .\ffmpeg.exe -f dshow -i audio="Stereo Mix (Realtek High Definition Audio)" -acodec libmp3lame  -ab 320k -f mp3 -probesize 32 -muxdelay 0.01 -y \\.\pipe\__audio_ffmpeg


  


  On the JS side the code is a little bit long, but essentially I am just reading a web socket and appending to buffer

  


  this.buffer = this.mediaSource.addSourceBuffer('audio/mpeg')


  


  Also as you see I tried to use -probesize 32 -muxdelay 0.01 flags, but no luck as well

  


  I tried to use plain tag as well, but still - this couple-of-seconds delay exists

  


  What can I do ? Am I missing something ? Maybe I have to disable buffering somewhere ?

  


• What does ffprobe -show_packets output means

  27 mai 2014, par Sajjad Ashraf

  When i run this command ffprobe -print_format json -show_packets -i sound.mp3 i get an array filled with small objects like these

          {
  
              "codec_type": "audio",
  
              "stream_index": 0,
  
              "pts": 3157032960,
  
              "pts_time": "223.712653",
  
              "dts": 3157032960,
  
              "dts_time": "223.712653",
  
              "duration": 368640,
  
              "duration_time": "0.026122",
  
              "size": "418",
  
              "pos": "3579819",
  
              "flags": "K"
  
          },

  What do these values mean, i am trying to get the frequencies of sound at every second. I have searched the ffmpeg and ffprobe documentation but no luck.