swresample.txt 2.12 KB
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    The official guide to swresample for confused developers.
   =========================================================

Current (simplified) Architecture:
---------------------------------
                        Input
                          v
       __________________/|\___________
      /                   |            \
     /    input sample format convert   v
    /                     | ___________/
    |                     |/
    |                     v
    |         ___________/|\___________              _____________
    |        /            |            \            |             |
    |   Rematrix          |          resample <---->|   Buffers   |
    |        \___________ | ___________/            |_____________|
    v                    \|/
Special Converter         v
    v         ___________/|\___________              _____________
    |        /            |            \            |             |
    |   Rematrix          |          resample <---->|   Buffers   |
    |        \___________ | ___________/            |_____________|
    |                    \|/
    |                     v
    |                     |\___________
    \                     |            \
     \   output sample format convert   v
      \_________________  | ___________/
                         \|/
                          v
                        Output

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Planar/Packed conversion is done when needed during sample format conversion.
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Every step can be skipped without memcpy when it is not needed.
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Either Resampling and Rematrixing can be performed first depending on which
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way it is faster.
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The Buffers are needed for resampling due to resamplng being a process that
requires future and past data, it thus also introduces inevitably a delay when
used.
Internally 32bit float and 16bit int is supported currently, other formats can
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easily be added.
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Externally all sample formats in packed and planar configuration are supported
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It's also trivial to add special converters for common cases.
If only sample format and/or packed/planar conversion is needed, it
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is performed from input to output directly in a single pass with no intermediates.