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• colors messed up (distorted) when making a gif from png files using ffmpeg

  13 novembre 2019, par wxyz

  I have a sequence of png images : image_00.png, image_01.png, image_02.png, etc. I want to convert them to a gif, so I tried the command

  ffmpeg -i image_%02d.png video.gif

  Unfortunately, the resulting gif has distorted colors. More specifically, it added a weird sort of yellow haze around some objects in the video.

  I also tried using the command above with all possible pixel format options (which I determined using the command ffmpeg -h encoder=gif) : rgb8, bgr8, rgb4_byte, bgr4_byte, gray, pal8. For example ffmpeg -i image_%02d.png -pix_fmt rgb8 video.gif. Unfortunately, all of the resulting gifs had some sort of color distortion.

  I also observed that this distortion does not occur if I convert the images to mp4 instead of gif. However, if I try converting that mp4 to a gif, I end up with the distortion again.

  How can I produce this gif without color distortion ?

• Weird cross platform support in ffmpeg

  31 mai 2022, par LmTinyToon

  I tried to build ffmpeg 4.4 library and link with it and I received multiple unresolved references. I came across on unusual architecture in ffmpeg for multiple platforms.The library has many places with code like this :

  


  void foo()
{
    // DO SOMETHING
    if (ARCH_MIPS) // maybe #if ARCH_MIPS (...) #endif should be used instead?
         foo_mips(...);
    if (ARCH_PPC)
        foo_ppc(c);
    if (ARCH_ARM)
         foo_arm(...);
    if (ARCH_AARCH64)
        foo_aarch64(...);
}


  


  This code leads to linker errors because there is no any stub methods for other platforms. I observed root MakeFile, it optionally includes platform dependent code for each library (path like $(LIB_SUBDIR)/$(ARCH)/MakeFile) where each foo_<arch></arch> is defined.

  


  So, how does it work ? In my opinion preprocessor directive #if should be used, otherwise we will receive unresolved reference on any platform. Maybe I missed something ? because this code appears frequently for example :

  


  

  1. utils.c : ff_yuv2rgb_init_tables_ppc

  


  2. swscale_unscaled.c : ff_get_unscaled_swscale_ppc, ff_get_unscaled_swscale_arm, ff_get_unscaled_swscale_aarch64

  


  3. cpu.c : ff_get_cpu_max_align_x86, ff_get_cpu_max_align_mips

  


  4. float_dsp.c : ff_float_dsp_init_aarch64, ff_float_dsp_init_ppc, ff_float_dsp_init_x86

  


  5. etc.

  


  


• lavc/mediacodec : rescale pts before decoding for both hw and sw buffers

  3 juillet 2017, par Aman Gupta

  lavc/mediacodec : rescale pts before decoding for both hw and sw buffers
  Replicates the logic used in the wrap_hw_buffer path to wrap_sw_buffer
  
  as well.
  Fixes decoding issues observed on AMLogic devices with
  
  OMX.amlogic.mpeg2.decoder.awesome, where the decoder would spit out a
  
  constant stream of "mPtsRecoveryCount" errors and decoded frames were
  
  returned in the incorrect order.
  Signed-off-by : Matthieu Bouron <matthieu.bouron@gmail.com>
  

  • [DH] libavcodec/mediacodecdec_common.c