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• avconv/ffmpeg to sync audio in a single file

  6 avril 2014, par Jeff Thompson

  I have an avi file with duration 1 hour. The audio rate is out of sync and ends about 2 minutes before the end of the video. I used the avconv -async option :

  avconv -i unsynced.avi -i unsynced.avi -acodec adpcm_ms -vcodec copy -map 0:0 -map 1:1 -async 1000 synced.avi

  But the output audio is still out of sync. Am I using the avconv command correctly to sync the audio with the video in the one input file ?

  Thanks,
   Jeff

• How to generate stereo sine wave using FFMPEG ?

  1er janvier 2020, par John Doe

  I’m trying to generate a stereo sine wave using FFMPEG (batch file), but have a different frequency for left and right. So far I have this :

  ffmpeg -f lavfi -i "sine=frequency=1000:duration=60" -ac 2 "binaural.wav"

  But it creates the same frequency for both left and right.
  Is this possible ?

• Streaming ALSA to rtsp stream using ffmpeg

  12 février 2019, par Demosthenes

  I would like to stream audio captured using an ALSA microphone with ffmpeg. I can capture the video to a file, what I want is ffmpeg to start an rtsp server which can be accessed by (multiple) clients in my local network. But I can’t even make it work with one client so far.

  What I tried so far :

  ffmpeg -f alsa -ac 1 -ar 44100 -i hw:1,0  -t 10 test.wav

  This is working perfectly. File is saved and can be played back. So input is alright.

  ffmpeg -f alsa -ac 1 -ar 44100 -i hw:1,0  -f rtsp rtsp_transport tcp rtsp://localhost:8090/live.sdp

  Trying this dry will result in an error it cannot connect to the server. Which is odd, I want to tell ffmpeg to start a server. So I’m starting one using

  ffserver ffserver.conf

  with a config file containing

  Port 8090
  
  BindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandwidth 1000
  
  CustomLog -
  
  NoDaemon
  
  <feed>
  
  </feed>

  This starts a server, or so it would seem. Now, trying the ffmpeg command from above again, I get

  [tcp @ 0x11d2490] Connection to tcp://localhost:8090?timeout=0 failed (Connection refused), trying next address
  
  Could not write header for output file #0 (incorrect codec parameters ?): Invalid data found when processing inputStream mapping:
  
    Stream #0:0 -> #0:0 (pcm_s16le (native) -> aac (native))
  
      Last message repeated 1 times

  So I thought, maybe I should state an output codec, so :

  ffmpeg -f alsa -ac 1 -ar 44100 -i hw:1,0 -codec:a libmp3lame -q:a 2  -f rtsp rtsp_transport tcp rtsp://localhost:8090/live.sdp

  which gives pretty much the same error, just with a different codec :

  [tcp @ 0x24d8630] Connection to tcp://localhost:8090?timeout=0 failed (Connection refused), trying next address
  
  Could not write header for output file #0 (incorrect codec parameters ?): Invalid data found when processing inputStream mapping:
  
    Stream #0:0 -> #0:0 (pcm_s16le (native) -> mp3 (libmp3lame))
  
      Last message repeated 1 times

  Any hints to what I am missing ?