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• FFmpeg CRF control using x264 vs libvpx-vp9

  19 octobre 2016, par igon

  I have some experience using ffmpeg with x264 and I wanted to do a comparison with libvpx-vp9. I tested a simple single pass encoding of a raw video, varying the crf settings and presets both with x264 and libvpx-vp9. I am new to libvpx and I followed this and this carefully but I might have still specified wrong combination of parameters since the results I get do not make much sense to me.

  For x264 I did :

  ffmpeg -i test_video.y4m -c:v libx264 -threads 1 -crf <crf> -preset <preset> -y output.mkv 
  
  </preset></crf>

  and obtained the following results :

  codec  , settings                        , time        , PSNR      ,bitrate
  
  libx264,['-crf', '20', '-preset', 'fast'],13.1897280216, 42.938337 ,15728
  
  libx264,['-crf', '20', '-preset', 'medium'],16.80494689, 42.879753 ,15287
  
  libx264,['-crf', '20', '-preset', 'slow'],25.1142120361, 42.919206 ,15400
  
  libx264,['-crf', '30', '-preset', 'fast'],8.79047083855, 37.975141 ,4106
  
  libx264,['-crf', '30', '-preset', 'medium'],9.936599016, 37.713778 ,3749
  
  libx264,['-crf', '30', '-preset', 'slow'],13.0959510803, 37.569511 ,3555

  This makes sense to me, given a crf value you get a value of PSNR and changing the preset can decrease the bitrate but increase the time to encode.

  For libvpx-vp9 I did :

  ffmpeg -i test_video.y4m -c:v libvpx-vp9 -threads 1 -crf <crf> -cpu-used <effort> -y output.mkv 
  
  </effort></crf>

  First of all I thought from tutorials online that the -cpu-used option is equivalent to -preset in x264. Is that correct ? If so what is the difference with -quality ? Furthermore since the range goes from -8 to 8 I assumed that negative values where the fast options while positive values the slowest. Results I get are very confusing though :

  codec     , settings                      , time        , PSNR     ,bitrate
  
  libvpx-vp9,['-crf', '20', '-cpu-used', '-2'],19.6644911766,32.54317,571
  
  libvpx-vp9,['-crf', '20', '-cpu-used', '0'],176.670887947,32.69899,564
  
  libvpx-vp9,['-crf', '20', '-cpu-used', '2'],20.0206270218,32.54317,571
  
  libvpx-vp9,['-crf', '30', '-cpu-used', '-2'],19.7931578159,32.54317,571
  
  libvpx-vp9,['-crf', '30', '-cpu-used', '0'],176.587754965,32.69899,564
  
  libvpx-vp9,['-crf', '30', '-cpu-used', '2'],19.8394429684,32.54317,571

  Bitrate is very low and PSNR seems unaffected by the crf setting (and very low compared to x264). The -cpu-used setting has very minimal impact and also seems that -2 and 2 are the same option.. What am I missing ? I expected libvpx to take more time to encode (which is definitely true) but at the same time higher quality transcodes. What parameters should I use to
  have a fair comparison with x264 ?

  Edit : Thanks to @mulvya and this doc I figured that to work in crf mode with libvpx I have to add -b:v 0. I re-ran my tests and I get :

      codec     , settings                                 , time        , PSNR     ,bitrate
  
  libvpx-vp9,['-crf', '20', '-b:v', '0', '-cpu-used', '-2'],57.6835780144,45.111158,17908
  
  libvpx-vp9,['-crf', '20', '-b:v', '0', '-cpu-used', '0'] ,401.360313892,45.285367,17431
  
  libvpx-vp9,['-crf', '20', '-b:v', '0', '-cpu-used', '2'] ,57.4941239357,45.111158,17908
  
  libvpx-vp9,['-crf', '30', '-b:v', '0', '-cpu-used', '-2'],49.175855875,42.588178,11085
  
  libvpx-vp9,['-crf', '30', '-b:v', '0', '-cpu-used', '0'] ,347.158324957,42.782194,10935
  
  libvpx-vp9,['-crf', '30', '-b:v', '0', '-cpu-used', '2'] ,49.1892938614,42.588178,11085

  PSNR and bitrate went up significantly by adding -b:v 0

• ffmpeg 4.3 build failure on Mac OS 10.12.6

  3 août 2020, par yay nay

  I have, by mistake, aborted the install of svtplay-dl via homebrew, while the gcc dependency was installing.
I did the "brew cleanup", after which the ffmpeg simply dissappeared from the command line.

  


  I have reinstalled the gcc to the latest available version (via homebrew) only to find the same error several times :

  


  enter code here"==> Installing dependencies for homebrew-ffmpeg/ffmpeg/ffmpeg: icu4c and x264


  


  ==> Installing homebrew-ffmpeg/ffmpeg/ffmpeg dependency : icu4c&#xA;==> ./configure —prefix=/usr/local/Cellar/icu4c/67.1 —disable-samples —disable-tests —enable-static —w&#xA;==> make&#xA;Last 15 lines from /Users/sejo/Library/Logs/Homebrew/icu4c/02.make :&#xA;./formatted_string_builder.h:227:9 : note : subexpression not valid in a constant expression&#xA;U_ASSERT(category <= 0xf),&#xA;^&#xA;../common/uassert.h:35:26 : note : expanded from macro 'U_ASSERT'&#xA;"#" define U_ASSERT(exp) void()&#xA;^&#xA;./formatted_string_builder.h:240:64 : note : in call to 'Field(0, 1)'&#xA;constexpr FormattedStringBuilder::Field kGeneralNumericField = UFIELD_CATEGORY_UNDEFINED, 1 ;&#xA;^&#xA;3 errors generated.&#xA;*** Failed compilation command follows : ----------------------------------------------------------&#xA;clang++ -DU_ATTRIBUTE_DEPRECATED= -DU_I18N_IMPLEMENTATION -DU_HAVE_STRTOD_L=1 -DU_HAVE_XLOCALE_H=1 -DU_HAVE_STRING_VIEW=1 -I. -I../common -O2 -W -Wall -pedantic -Wpointer-arith -Wwrite-strings -Wno-long-long -std=c++11 -Qunused-arguments -Wno-parentheses-equality -Wglobal-constructors -fvisibility=hidden -fno-common -c -MMD -MT numfmt.d numfmt.o numfmt.ao -o numfmt.ao numfmt.cpp&#xA;--- ( rebuild with "/Library/Developer/CommandLineTools/usr/bin/make VERBOSE=1 all" to show all parameters ) --------&#xA;make[1] : *** [numfmt.ao] Error 1&#xA;make : *** [all-recursive] Error 2

  &#xA;

  Do not report this issue to Homebrew/brew or Homebrew/core !

  &#xA;

  Error : You are using macOS 10.12.&#xA;We (and Apple) do not provide support for this old version.&#xA;You will encounter build failures with some formulae.&#xA;Please create pull requests instead of asking for help on Homebrew's GitHub,&#xA;Discourse, Twitter or IRC. You are responsible for resolving any issues you&#xA;experience while you are running this old version."

  &#xA;

  The previous version of gcc was 4.2.2, installed with -libfdk (which I really needed) and it worked without any problem.

  &#xA;

  Is there any solution to this (it seems) newly aroused issue with ffmpeg with homebrew on Mac OS 10.12 ?

  &#xA;

• Failed to capture a avi file using opencv

  30 avril 2017, par Wei

  I am quite new to c++ compilation. I am trying to work on a simple problem using opencv where I read a video file and display it.

  My code looks like :

  #include <opencv></opencv>cv.h>
  
  #include <opencv></opencv>highgui.h>
  
  #include "opencv2/opencv.hpp"
  
  #include <opencv2></opencv2>core/core.hpp>
  
  #include <opencv2></opencv2>highgui/highgui.hpp>
  
  
  
  
  
  #include 
  
  #include 
  
  
  
  #include <algorithm>
  
  #include 
  
  #include 
  
  #include 
  
  #include <fstream>
  
  #include <iostream>
  
  #include <vector>
  
  #include <list>
  
  #include <string>
  
  
  
  
  
  using namespace cv;
  
  
  
  IplImage* image = 0; 
  
  IplImage* prev_image = 0;
  
  
  
  int show = 1; 
  
  
  
  int main( int argc, char** argv )
  
  {
  
      int frameNum = 0;
  
  
  
      char* video = argv[1];
  
      VideoCapture capture(video);
  
  
  
      if( !capture.isOpened() ) { 
  
          printf( "Could not initialize capturing..\n" );
  
          return -1;
  
      }
  
  
  
      if( show == 1 )
  
          cvNamedWindow( "Video", 0 );
  
  
  
      while( true ) {
  
          IplImage* frame = 0;
  
          int i, j, c;
  
  
  
          // get a new frame
  
          //frame = cvQueryFrame( capture );
  
          Mat mat_img;
  
          capture >> mat_img;
  
          IplImage frame1 = mat_img.operator IplImage();
  
          frame = &amp;frame1;
  
          if( !frame )
  
              break;
  
  
  
          if( !image ) {
  
              image =  cvCreateImage( cvSize(frame->width,frame->height), 8, 3 );
  
              image->origin = frame->origin;
  
          }
  
  
  
          cvCopy( frame, image, 0 );
  
  
  
          if( show == 1 ) {
  
              cvShowImage( "Video", image);
  
              c = cvWaitKey(3);
  
              if((char)c == 27) break;
  
          }
  
  
  
          std::cerr &lt;&lt; "The " &lt;&lt; frameNum &lt;&lt; "-th frame" &lt;&lt; std::endl;
  
          frameNum++;
  
      }
  
  
  
      if( show == 1 )
  
          cvDestroyWindow("Video");
  
  
  
      return 0;
  
  }
  
  </string></list></vector></iostream></fstream></algorithm>

  Then I compile it like :

  g++ test.cpp -o Video -pipe -D __STDC_CONSTANT_MACROS -D STD=std -Wall -I. -I/usr/local/ -O3 -DNDEBUG -ggdb -L/usr/local/ -lopencv_core -lopencv_highgui -lopencv_video -lopencv_imgproc -lavformat -lavdevice -lavutil -lavcodec -lswscale

  Compilation works fine and no errors returned.

  However, when I was running it, I got :

  (Video:5651): GLib-GObject-CRITICAL **: g_object_set: assertion 'G_IS_OBJECT (object)' failed
  
  Could not initialize capturing..

  Some other information :
  1. I test my opencv and ffmpeg by running simple examples, which work well.
  2. I can stream frames from my camera and display it using opencv.

  Anyone has idea of what causes this ?

  Any idea is appreciated.