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• RGB to YUV422 conversion with ffmpeg, incorrect colors

  22 janvier 2016, par user3578571

  I’m trying to convert an 8bit RGB uncompressed to an mpeg2 mxf file (xdcam 422 HD 1080 50i) which is YUV422. With info from the FFMpeg docs and various websites i made the following command :

  ./ffmpeg -y -i test_lines.mov  -pix_fmt yuv422p -vcodec mpeg2video -non_linear_quant 1 -flags +ildct+ilme -top 1 -dc 10 -intra_vlc 1 -qmax 2 -vtag xd5c -rc_max_vbv_use 1 -rc_min_vbv_use 1 -g 12 -b:v 50000k -minrate 50000k -maxrate 50000k -bufsize 8000k -acodec pcm_s24le -ar 48000 -bf 2 -ac 2 lines_HD.mxf

  This gave me a result with the colors much brighter than the original.

  So i tried adding the options -color_range 1 -colorspace 1 -color_primaries 1 -color_trc 1 but this didn’t seem to do anything.

  After adding colormatrix=bt601:bt709 i got a way better image, but slightly darker than the original and it also feels weird specifying this option cause the source is also in the REC709 colorspace, so why specify it differently ?

  Next i regenerated my source image to an YUV codec (prores) and rerun FFMpeg on it with the colors coming out just fine. Therefore i think it has to be an RGB -> YUV problem.
  Does somebody have an idea how to this properly ? I can provide screenshots of the different results on a videoscope as soon as i’m back at the office, if anybody is interested.

  Last, i know there are various topics touching this subject but either they go way over my head FFmpeg wise or bring me to the stage where i already am.

• Unable to link QtFFmpegWrapper sample on Win7 with VS 2012

  20 juillet 2014, par mschwarz

  I am trying to incorporate QtFFmpegWrapper in my program, but both my program and the provided sample won’t link with ffmpeg :

  QVideoEncoder.obj:-1: Error: LNK2019: unresolved external symbol _avcodec_init referenced in function "protected: bool __thiscall QVideoEncoder::initCodec(void)" (?initCodec@QVideoEncoder@@IAE_NXZ)
  
  QVideoDecoder.obj:-1: Error: LNK2001: unresolved external symbol _avcodec_init
  
  QVideoEncoder.obj:-1: Error: LNK2019: unresolved external symbol _avcodec_thread_init referenced in function "public: bool __thiscall QVideoEncoder::createFile(class QString,unsigned int,unsigned int,unsigned int,unsigned int,unsigned int)" (?createFile@QVideoEncoder@@QAE_NVQString@@IIIII@Z)
  
  QVideoEncoder.obj:-1: Error: LNK2019: unresolved external symbol _avcodec_open referenced in function "public: bool __thiscall QVideoEncoder::createFile(class QString,unsigned int,unsigned int,unsigned int,unsigned int,unsigned int)" (?createFile@QVideoEncoder@@QAE_NVQString@@IIIII@Z)

  and 10 or so more like these ...

  Why do these pop up when linking ? The libs are all there and found, it just seems like the linker has issues with them ...

  I use the following setup for my project :

  • Latest QtFFmpegWrapper from https://code.google.com/p/qtffmpegwrapper/
  • qt-opensource-windows-x86-msvc2012_opengl-5.3.0
  • Visual Studio 2012 Professional
  • Qt Creator 3.1.2
  • ffmpeg builds from http://ffmpeg.zeranoe.com/builds/ :
  • ffmpeg-20140717-git-fa6716c-win32-dev
  • ffmpeg-20140717-git-fa6716c-win32-shared

  Everything is 32Bit.

• extracting quantization matrix in jpeg conversion and residual error in mpeg conversion in ffmpeg ?

  31 juillet 2017, par Saeid Zangeneh

  Im not familiar with the ffmpeg source code and I’m not so professional in programming to can change or find out the code.I just want to extract quantization matrix in jpeg conversion also the residual error in mpeg conversion.