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• How do I concat two video mp4 files, each of which has an audio of different sample rates with ffmpeg

  14 août 2020, par Geo

  I have two videos : video1.mp4 and video2.mp4 in the configured txt file, both videos have mp3 audios :
video1.mp4 has : Audio : mp3, 32000 Hz, mono, fltp, 48 kb/s
video2.mp4 has : Audio : mp3, 24000 Hz, mono, fltp, 32 kb/s
I need to keep the different sample rates since I need to change the pitch to make it sound different from the real voice of the person, now I tried to merge the two videos by concatenating them :

  


  ffmpeg -safe 0 -f concat -segment_time_metadata 1 -i videoconf.txt -vf select=concatdec_select -af aselect=concatdec_select,aresample=async=1 -y videoout.mp4

  


  but I got a lot of errors like these :

  


  [aac @ 0x730e491e00] channel element 2.12 is not allocated

  


  index.js:81 Error while decoding stream #0:1 : Invalid data found when processing input

  


  index.js:81 [aac @ 0x730e491e00] TYPE_FIL : Input buffer exhausted before END element found

  


  index.js:81 Error while decoding stream #0:1 : Invalid data found when processing input

  


  ......

  


  So how can I concatenate multiple videos with different audio sample rates inside each video ?
By the way, when the sample rates are the same for all the audios inside each video, the concat works like a charm.

  


  Thanks

  


• Ffmpeg speed up image extractio from higher quality video [closed]

  29 octobre 2020, par Expressingx

  I'm using ffmpeg and mage to create thumbnails for our web client. This is current fastest implementation I've found. However if the video quality is higher (e.g. full hd) it still takes a lot of time for 15 min video duration.

  


  Mage is used to create sprite image from the generate images and the .vtt file is manually created from the code. Those 2 are fast, so I have no concerns with them.

  


  Ffmpeg command

  


  ffmpeg.exe -loglevel panic -i video.mp4 -q:v 8 -vf "select=not(mod(n\,30)),scale=120:80" -vsync 0 -frame_pts 1 .\test\frame-%d.jpg


  


  I'm generating the jpegs with their frame time as name so I can parse and correctly display them in the client.

  


  Is there a way to make it faster ?

  


• Re-streaming RTSP with higher FPS

  4 février 2021, par AndBondStyle

  I have RTSP stream with very low and non-constant FPS (varying between 0.2 ... 0.5). It is generated using -skip_frame flag to reduce network and CPU usage as much as possible :

  


  ffmpeg -skip_frame nointra -i  -vsync 2 -f rtsp 


  


  As a consequence, it takes a very long time (1 ... 3 minutes) to connect to that stream and see first meaningful image. I want this stream to work with generic players without any tweaks, so my decision was to re-stream it with higher FPS (10, to be exact) :

  


  ffmpeg -i  -vf "fps=fps=10,setpts=N/(10*TB)" -f rtsp 


  


  Not entirely sure how that command is working, but it somehow did the trick and reduced connection time to about 5 seconds. However, I suspect that it's outputting frames in bursts, which is not ideal. For example, if original low-fps stream contains 2 frames which are 3 seconds apart, my re-stream command (probably) does the following :

  


  

  • When the first input frame comes, output a bunch of frames as fast as possible

  


  • Don't output anything for an entire 3 seconds

  


  • When the second frame comes, output 3 * 10 = 30 frames as fast as possible

  


  • Sleep again until new input frame shows up...

  


  


  Is there a way to make my re-stream command output frames evenly (with a constant FPS) ? Or maybe there's another way to reduce RTSP connection (buffering ?) time ?