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• Concatenate two mp4 files using FFmpeg with Android

  4 juillet 2013, par vijay

  I need to merge video files in Android using FFmpeg.I used the code from halfninja and passed the following parameters to run method in Videokit.c.

  ffmpeg -i "concat:input1.mpg|input2.mpg" -c copy output.mpg

  It causes error when these parameters are passed from Android through JNI. Then i replaced -c copy with -vcodec copy -acodec copy.It worked fine.

  Now i tried to concat two .mp4 files / two .3gp files by using the above method and my output format is mp4.The output file is generated but it is empty(0kb).

  When i googled it out, i was asked to convert all mp4 or 3gp files into mpg and then concat it and again convert back to mp4 in the following post :

  Concatenate mp4 files in Android using halfninja ffmpeg (Refer Steven Penny's answer).

  But i have problems(only first input file is converted and the app exits) when converting and storing the intermediate file(i am calling run method thrice).Also this method stores all the input files in the device sdcard and this should not be done.

  -c copy works fine when passing parameters for ffmpeg executable(generated when ndk-build is made) through terminal but it throws an error "unrecognized option c" when called through JNI from android device.Can anyone let me know why this happens ?

  When we look at Steven's answer, we have to call the run method multiple times to covert all the input files and one more time to concat all these.Is it possible to it in a single call ?

  Is it possible to concat video files with different formats without storing the input files in device(mp4+mp4, mp4+3gp,3gp+3gp are my possible combinations of input) ?

  Any help is appreciated.

• could use some help on ffprobe

  27 décembre 2016, par Telkoboy

  I’m currently running the following command and it’s giving me mostly what I need, but I would like to also have it include the file name.

  for %%A IN (%VAR0%\*.wav) DO "C:\program files (x86)\ffmpeg\bin\ffprobe" -i "%%A" -show_entries format=duration -v quiet -of csv="p=0" >>output.txt

  The above produces this :

  110.994375

  This is great, but what I would really want is something like this as I need to import this data into a db for further processing. I need to know which file the 110.9943765 came from.

  recording1.wav, 110.994375

  Thanks,

  Steven

• ffmpeg filter_complex multiple overlays - why are they not syncing properly

  28 décembre 2023, par howdood

  I'm setting up live streaming using three overlaid inputs in ffmpeg. O:v is a webcam directly connected to the streaming box (a headless linux box) while 2:v and 3:v are ultra-low latency UDP streams from two remote R-Pis.

  


  The filter_complex argument I'm using (that works, with all three video inputs perfectly in sync) is
[0:v] fifo [v1] ;[2:v] fifo [v2] ; [3:v] fifo [v3] ;[v1]setpts=PTS-STARTPTS[sync1] ;[v2]setpts=PTS-STARTPTS[sync2] ; [v3]setpts=PTS-STARTPTS+5/TB [sync3] ;[sync1][sync2] overlay=x=W-w:y=H-h [out1] ;[out1][sync3] overlay=x=0:y=H-h [vfinal]

  


  Two questions about this :

  


  


  1. Why am I having to add +5/TB to [sync3] via setpts (in bold above) ? If I omit that, [3:v] is synced in to the stream noticeably ahead of the other two inputs. My best guess is that this may be to compensate for the processing time of the first overlay [sync1][sync2] which is introducing extra latency into that part of the stream. Is that right ?

     


  


  2. Importantly - the value of the extra pts compensation has to be dialed in by hand and will be specific to the underlying hardware used. Is there a way of getting ffmpeg to calculate this automatically so I don't have to worry about keeping in dialed in, in production ?

     


  


  


  Thanks for reading ! I'm at the limit of the ffmpeg docs here...