[FFmpeg-devel] [PATCH 4/9] avfilter/overlay_subs: Add overlay_subs filter

[Nicolas George]

Nicolas George (12021-08-19):
> This is not that hard to do. As I pointed, I already started working on
> it. It would have gone faster if there were other people interesting in,
> reviewing the code trustfully and offering useful suggestions.

This is the notes I have taken about format negotiation.

avfilter_graph_config()

  graph_config_formats()

    query_formats()
      filter->query_formats()
      ff_merge_*()

    reduce_formats()
      = if input has only one format, try to keep only it on output

    swap_sample_fmts()
      = if input has only one format, put the most similar first on outputs

    swap_samplerates()
      = if input has only one sample rate, put the closest first on outputs

    swap_channel_layouts()

    pick_formats()

  graph_config_links()
  graph_check_links()
  graph_config_pointers()

The goal now is to describe every step of the negotiation in the
AVFilterNegotiation structure. Right now, the merging step is done. I
will be looking at the reduce and swap code now.

If you want to help, you can start getting familiar with how it works.

-- 
  Nicolas George
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