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• How to avoid a growing delay with ffmpeg between sound and raw video data ?

  13 novembre 2011, par roland

  Hello everybody and thank you for reading !

  Here is my problem : I have a program piping raw video frames to the standard output. This program is using OpenCV to capture and process the video and outputs directly the processed frames. The loop is synced to the framerate I chose. I'm using ffmpeg to read from the standard input and everything works fine for the video.
  But now that I added the sound I have a big problem : a growing delay is occuring and I really need to get rid of it. So here is my idea, but I really need your help :

  I have to find a way to include a timestamp information to the raw video. To be understandable by ffmpeg, it needs to be a known raw video compatible container. And then I will need to use the container API and pipe it to the standard output in my program. I really do not know what to use in the jungle of video formats and codecs, and I don't event know how to enable timestamp synchronizing in ffmpeg...

  If anyone has an idea, i am really interested here. For information, here is the command line i use to pipe the raw video :

  ./myprogram | ffmpeg -y -f alsa -i pulse -ac 2  -f rawvideo -vcodec rawvideo -r 24 -s 640x480 -pix_fmt bgr24 -i - -vcodec libx264 -pix_fmt yuv420p -r 24 -f flv -ar 44100 out.flv;

  Thand you very much,

  Roland

• ffmpeg video encoding for mobile devices

  27 janvier 2012, par TimGL

  I'm trying to encode the video file from f4v to mp4 for mobile devices and using 2 different ffmpeg versions with the same configuration files. Encoding goes ok for both files. The one that I convert using ffmpeg version N-32754-g936d4d4-Sherpya failing to play on my blackberry.
  This is the command line that I'm using :

  ffmpeg.exe -i some.avs -vcodec libx264 -b 500k -r 24 -acodec libfaac -ab 128k -ar 48000 -ac 2 -threads 0 -coder 0 -bf 0 -refs 1 -level 30 -maxrate 10000000 -bufsize 10000000 -y test.mp4

  The vido playes ok when I convert it using FFmpeg version SVN-r13712
  Could you give me some light on where the issue couls be ?

• FFMPEG - Watermark video with same quality and filesize

  29 mars 2012, par ddlshack

  I have some videos, and I'd like to watermark them with a transparent PNG. Here's what I've tried :

  ffmpeg -i 9.flv -vf "movie=logo.png [watermark];[in][watermark] overlay=10:10 [out]" 9_w.flv

  However, bitrate or quality is not preserved. Preferably I'd like ffmpeg to re-encode the file with exactly the same settings as the original file (same codecs, bitrate). If thats not easily possible, I'd like to encode with a specific codec, but preserving 'quality', however that is measured.