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• Why are the red words blurred after opencv and ffmpeg screenshots from a video capture card ? [closed]

  28 août 2024, par yaxin xing

  I tried to take a screenshot after getting the video stream through the video capture card, but the words in red font become blurry after taking the screenshot, but setting the video format to XRGB format in OBS makes it clear. How can I solve this problem in python ?

  


  As you can see in the picture, the red letters are much less clear than the other colors
enter image description here

  


  I tried to capture a frame in ffmpeg and set -pix_fmt but it's still blurry, I tried 4:4:4 color modes like nv12, yuv444, rgb24, etc. but it doesn't work.

  


  I also tried passing ffmpeg's video stream to opencv via pipe, but opencv's recombination of its color channels when converting the video stream caused the colors to change, and didn't solve the problem of the red font not being clear either

  


• How to understand H264/MP4 byte stream [on hold]

  19 janvier 2018, par elpha01

  I am actually working on stream data and I have few problems that questioned me.

  In a h264 stream, is there any byte data representing the start point and the end point of the stream or are the first bytes representing the first frame and can be removed for removing the frame ? Is it the same for a .264 file ?

  Are NAL units corresponding the frames of the stream ? Is there exactly one NAL unit per frame ? Are all NAL units have their header 00 00 00 01 ? What is a NAL unit with no 32 bit size

  What are SPS and PPS ? Is there exactly one of them per stream ? Are they necessary or optionnal ?

  Is a mp4 stream can makes sense or is it a H264 stream ?
  How can we recognize a mp4 stream and a H264 stream by looking byte data ?

  What does this error mean ?
  "Format h264 detected only with low score of 1, misdetection possible !"

  I am actually receiving from a third party CCTV software a byte array for each frame. I don’t know if it’s a mp4 or h264 stream, I wonder if the data are even valid. I need to create a RTSP server and I’m using RTSP Sharp which seems to work very well. I should separate the byte data with the NAL unit, the SPS and the PPS.

  Any indication that could help me to understand this codec would be appreciated.

• avformat/rmdec : when reading audio blocks, dont leave holes when reading fails

  9 janvier 2014, par Michael Niedermayer

  avformat/rmdec : when reading audio blocks, dont leave holes when reading fails
  The fate test is changed because the reference file depends on the use of
  
  non cleared data at the very
  
  end. Alternatively we could upload a new reference file, though that would
  
  then have to be changed every time the handling of a truncated frame changes
  
  or theres a change to error concealment, each time adding a new file ...
  Fixes use of uninitialized memory
  
  Fixed : msan_uninit-mem_7f3c02b81363_2787_RLG2_19.rm
  
  Found-by : Mateusz "j00ru" Jurczyk and Gynvael Coldwind
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/rmdec.c
  • [DH] tests/fate/real.mak