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• ffmpeg android : change the speed of video and audio

  2 octobre 2015, par John

  I am working on Android platform with ffmpeg, I’ve built the ffmpeg and run as ’run-time’ command for my android app.

  I’ve tested some function like video trim, it’s working :

  ffmpeg -i /sdcard/vpai/in.mp4 -ss 5 -t  5 -c:v copy -c:a copy /sdcard/vpai/out.mp4

  merge video and audio, also working :

  ffmpeg -i /sdcard/vpai/in.mp4 -i /sdcard/vpai/in.mp3 -c:v copy -c:a copy /sdcard/vpai/out1.mp4

  But when I try to speed up the video, it’s not working, the command is :

  ffmpeg -i /sdcard/vpai/in.mp4 -filter_complex '[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]' -map '[v]' -map '[a]' /sdcard/vpai/output.mp4

  I execute the exact same command on desktop, its working fine, but not working on the Android...

  The error message :
  Invalid stream specifier :"[v]".
  Last message repeated 3 times
  Stream map "[v]" matches no streams.

  Any one can help ?

• avfilter/vsrc_mandelbrot : Fix speed regression

  24 novembre 2015, par Michael Niedermayer

  avfilter/vsrc_mandelbrot : Fix speed regression
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavfilter/vsrc_mandelbrot.c

• How to speed up my video creating/encoding pipeline

  23 septembre 2015, par user606521

  I am creating a video from 120 JPEG images and concatening it with intro video.

  • video (and images) dimmensions : 960x540
  • video/audio output format that I need : mp4 H.264, AAC

  I am creating video from JPEG images using following command :

  ffmpeg -f lavfi -i anullsrc -r 60 -i pipe:0 -y -acodec aac -strict experimental \
  
  -shortest -movflags frag_keyframe+empty_moov -f mp4 video.mp4

  It creates 2 seconds (120 frames with 60FPS) mp4 video with "silence" (silent audio). video.mp4 size is 94KB. This process takes 1 second. (Note that I am passing images through pipe:0).

  Next I concatenate it with existing intro.mp4 video (H.264, AAC, 931KB, lasts 6 seconds) using following command :

  ffmpeg -i intro.mp4 -i video.mp4 -y \
  
  -filter_complex "[0:0] [0:1] [1:0] [1:1] concat=n=2:v=1:a=1 [v] [a]" \
  
  -map "[v]" -map "[a]" -acodec aac -strict experimental \
  
  -movflags frag_keyframe+empty_moov -f mp4 final.mp4

  It creates final mp4 H.254, AAC video which lasts 2 + 6 = 8 seconds and it’s size 990KB. This process takes 3.5 seconds.

  So the whole process takes 5.5 seconds on my Mac. I have to speed it up, especially concatening videos. I am not familiar with video encoding and video formats, but I thought that maybe creating first video in mp4 and then concatening it with another mp4 video is not efficient. Are there any other formats in which I could create video (and intro) that will be faster to create/concatenate so I could encode only final video as mp4 ?

  For example I could create video.<format></format>, concatenate it with intro.<format></format> and finally encode it as final.mp4.

  Use case : I have to create videos in almost real time. 5.5 secs is ok on my Mac, but I have to execute my app on a weaker machine on which this process currently takes 3 + 15 = 18 seconds.

  Also maybe there are some cool flags I could pass to ffmpeg to make it faster ?