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• Encoding H.264 CBR videos with FFmpeg

  27 août 2015, par Cornstalks

  I’m trying to encode a video with ffmpeg into H.264 (via the libx264 library) with a constant bit rate. I know, I know, VBR is often preferred, but for this specific job I’m required to use CBR (just as long as it’s so many kilobytes per second ; it doesn’t have to be an exact kilobytes per frame, afaik). My sample video I’m using to test is from here : http://a1408.g.akamai.net/5/1408/1388/2005110403/1a1a1ad948be278cff2d96046ad90768d848b41947aa1986/sample_iTunes.mov.zip (it comes from http://support.apple.com/kb/HT1425)

  I can get a constant bit rate when encoding the video with MPEG-4 Video (using the commands ffmpeg -i sample_iTunes.mov -b 819968 -minrate 819968 -maxrate 819968 out.mov), and the bit rate is as expected. Reading the video’s specs via the QuickTime Inspector, it’s got a data rate of 844.94 kbit/s. Cool.

  However, when I change the codec to libx264, it seems to completely ignore my bitrate requests ! The command I’m trying is "ffmpeg -i sample_iTunes.mov -vcodec libx264 -vpre medium -b 819968 -vb 819968 -minrate 819968 -maxrate 819968 -bufsize 400000 test.mov". But when I check the video’s specs via the QuickTime Inspector, it’s got a data rate of 254.74 kbit/s. WTF ? That’s not even close !

  I’ve tried changing so many parameters and adding tons of different things, and I’ve spent 2 days googling this, but I can’t seem to get it to work. If I encode the video with the MainConcept H.264 encoder, I can get a constant bitrate, but I need this to work with ffmpeg.

  If someone can help me figure out how to do CBR H.264 encoding with FFmpeg, I will love you forever !

• Revision a4ad3809e2 : Make RDCOST() results 64-bit. This prevents various integer overflows that seve

  2 août 2012, par Ronald S. Bultje

  Changed Paths : Modify /vp8/encoder/encodemb.c Modify /vp8/encoder/rdopt.c Modify /vp8/encoder/rdopt.h Make RDCOST() results 64-bit. This prevents various integer overflows that several of us have been seeing in the past few days. Change-Id : (...)

• while build a demo about ffmpeg , it occurs : undefined reference to `av_register_all'

  8 juin 2016, par Cody

  This problem has bothered me for days.

  After I compile and install ffmpeg , I try to build a demo using it, but it always fails.

  The demo is :

  #include "libavcodec/avcodec.h"
  
  #include "libavformat/avformat.h"
  
  
  
  int main(int argc,char *argv[]) {
  
      av_register_all();
  
      return 1;
  
  }

  With gcc main.c -o main.o, an error occurs : undefined reference to 'av_register_all'

  Building with : gcc main.c -o main.o  -lm -ld -lz -lavcodec -lavformat -lavutil, another error occurs : /usr/bin/ld: cannot find -ld

  How can I resolve this ?