ffmpeg/doc/swresample.txt

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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.
Either Resampling and Rematrixing can be performed first depending on which
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way it is faster.
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.
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
is performed from input to output directly in a single pass with no intermediates.