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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 !

  


• avcodec/v4l2_buffers : Fix infinite loop

  27 octobre 2019, par Andriy Gelman

  avcodec/v4l2_buffers : Fix infinite loop
  This part of the code counts the number of planes returned by the v4l2
  
  device for each queried capture/output buffer.
  
  When testing the GPU h264 encoder on Nvidia's Jetson Nano, this caused an
  
  infinite loop because avbuf->buf.length included some empty buffers (i.e.
  
  where avbuf->buf.m.planes[i].length = 0), meaning that the counter was
  
  never incremented and break was never reached.
  
  This is fixed in the commit by using a well defined iteration range.
  Signed-off-by : Aman Gupta <aman@tmm1.net>
  

  • [DH] libavcodec/v4l2_buffers.c

• Link ffmpeg to Pydub in Serverless layer

  15 mars 2021, par akai

  I'm using the Serverless framework to deploy an app on AWS. I have created a layer, defined as follows in serverless.yml :

  


  layers:
  ffmpeg:
    path: layer


  


  I also excluded it from the main file bundle :

  


  package:
  exclude:
    - layer/**


  


  and defined a lambda function :

  


   cut_audio:
    layers:
      - {Ref: FfmpegLambdaLayer}


  


  In this function I use the Pydub library, which needs to access the ffmpeg layer. At the moment I have the following error FileNotFoundError: [Errno 2] No such file or directory: 'ffprobe', meaning I have to link ffmpeg as AudioSegment.converter(path)

  


  How do I get the path of my layer ?

  


  Edit : could I solve this by bundling both Pydub and ffmpeg in the layer ?

  


  Edit 2 : the eziotedeschi/AWS-Lambda-Layer-Pydub github repository doesn't seem to help. I get the following error No module named 'pydub'. I am using Python3.8 as runtime, that might be the issue.