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• What does the left_block_options array represent in the fill_decode_neighbors function of FFmpeg？

  28 décembre 2024, par mike xu

  I am studying the source code of FFmpeg, specifically the fill_decode_neighbors function. I am trying to understand how the decoding process works, especially the usage of the left_block_options array.
Here is the relevant code snippet :

  


  static const uint8_t left_block_options[4][32] = {
        { 0, 1, 2, 3, 7, 10, 8, 11, 3 + 0 * 4, 3 + 1 * 4, 3 + 2 * 4, 3 + 3 * 4, 1 + 4 * 4, 1 + 8 * 4, 1 + 5 * 4, 1 + 9 * 4 },
        { 2, 2, 3, 3, 8, 11, 8, 11, 3 + 2 * 4, 3 + 2 * 4, 3 + 3 * 4, 3 + 3 * 4, 1 + 5 * 4, 1 + 9 * 4, 1 + 5 * 4, 1 + 9 * 4 },
        { 0, 0, 1, 1, 7, 10, 7, 10, 3 + 0 * 4, 3 + 0 * 4, 3 + 1 * 4, 3 + 1 * 4, 1 + 4 * 4, 1 + 8 * 4, 1 + 4 * 4, 1 + 8 * 4 },
        { 0, 2, 0, 2, 7, 10, 7, 10, 3 + 0 * 4, 3 + 2 * 4, 3 + 0 * 4, 3 + 2 * 4, 1 + 4 * 4, 1 + 8 * 4, 1 + 4 * 4, 1 + 8 * 4 }
    };


  


  While I understand that this array plays a role in determining neighboring blocks for decoding, I am unclear about :

  


  The specific meaning of the array values.
How this array interacts with the decoding process, especially in relation to intra-prediction or block positioning.
Instead of a detailed explanation, I would greatly appreciate :

  


  Any keywords I can look up to understand this topic better (e.g., terms from the H.264 standard or FFmpeg documentation).
Links to related documentation, articles, or sections in the H.264 specification.
Suggestions on where I might find similar examples or detailed discussions about intra-block neighbor handling in FFmpeg.
Thank you for any resources or pointers you can provide !

  


• Naming convention to create/merge multiple video files

  25 octobre 2015, par Anay Bose

  I am trying to concat a few .mp4 files. I first create intermediate .mpg clips, and then merge them together with ’cat’ command ; then convert it to .mp4 files

  for example,

  ffmpeg -i input1.mp4 -qscale:v 1 intermediate1.mpg
  
  ffmpeg -i input2.mp4 -qscale:v 1 intermediate2.mpg

  // Now merge them together

  cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
  
  ffmpeg -i intermediate_all.mpg -qscale:v 2 output.mp4

  Now, I would like to merge all .mpg files within a directory
  the following command works if I have max 9 .mpg files

  cat folder/*.mpg > intermediate_all.mpg

  But, if I got more then 9 .mpg files, the movie sequence breakes, meaning no. 10 clip shows up after no. 1 clip which I do not want. Is there any naming convention that I can follow with ffmpeg. In imagemagick, I can easily use the following syntax and it works, but in ffmpeg it is not working.

  cat folder/%d.mpg or cat folder/%d.mpg[0-10] 

• avdevice/x11grab : rename the "w" Window to "root" in paint_mouse_pointer

  8 septembre 2014, par Antonio Ospite

  avdevice/x11grab : rename the "w" Window to "root" in paint_mouse_pointer
  This specifies better the meaning of the variable, and is also in
  
  preparation of a subsequent change which will introduce a temporary
  
  Window variable for which "w" is an good name.
  Signed-off-by : Antonio Ospite <ao2@ao2.it>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavdevice/x11grab.c