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• ftp: reconnect on read

  27 mai 2013, par Lukasz Marek

  ftp: reconnect on read
  FTP server may disconnect after some period of time when no transfer is done.
  FTP protocol should reconnect and seek to last position.
  

  • [DH] libavformat/ftp.c

• ffmpeg : two videos side-by-side with audio1 lang=ger & audio2 lang=eng

  19 janvier 2023, par miridigital

  I have two videos from two GoPro cameras. Both videos are rendered via ffmpeg side-by-side into a single video (left and right) and the audio is currently combined/mixed into two channels (stereo). I can hear both camera audio channels at the same time.

  


  Two channels stereo :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" -ac 2 side-by-side.mp4


  


  audio from both videos mixed into a single file with 2 channels - mediainfo

  


  Now I want to switch between the two audio channels (cam1 or cam2) while I'm playing the side-by-side video.

  


  My first try : With four channels (without -ac 2 parameter) :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" side-by-side.mp4


  


  audio from both videos mixed into a single file with 4 channels - mediainfo

  


  But the most video players can't easily select the channels 1+2 or 3+4 while playing.

  


  So I tried two languages :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" -metadata:s:a:0 language=ger -metadata:s:a:1 language=eng side-by-side.mp4


  


  audio from both videos mixed into a single file with 4 channels with languages - mediainfo

  


  But that's wrong. I can only see german with 4 channels. How can I put channels 1+2 into german and channels 3+4 into english ? Afterwards I should be able to use the multi language feature from most video players to switch the audio between cameras.

  


  Thank you,
  
Miriam

  


• ffmpeg unique frames only

  5 novembre 2013, par William

  I have a video sequence (MPEG1) of 30 fps that is decoded in two ways :

  • opencv_ffmpeg returns 30 images per second, but only 5 of them are unique, while all others are clones of the unique ones.

  • proprietary players (MediaPlayer) returns only the 5 unique frames and "holds" them for (1/5) sec each.

  Is there a way to grab only the unique frames that the coder knows and not the total amount the ffmpeg decoder produces to fulfill the fps rate ?

  I'm developing a tracker and my tracker is forced to run 6 times slower and do many mistakes due to these "cloned frames".

  Does anyone know any technical term to the problem ? Unfortunately, ffmpeg is a black box for an opencv user and the documentation is sparse.