[deb_ffmpeg.git] / ffmpeg / doc / swresample.txt

    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

Planar/Packed conversion is done when needed during sample format conversion.
Every step can be skipped without memcpy when it is not needed.
Either Resampling and Rematrixing can be performed first depending on which
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
easily be added.
Externally all sample formats in packed and planar configuration are supported
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.
Commit	Line	Data
2ba45a60 DM	1	The official guide to swresample for confused developers.
	2	=========================================================
	3
	4	Current (simplified) Architecture:
	5	---------------------------------
	6	Input
	7	v
	8	__________________/\|\___________
	9	/ \| \
	10	/ input sample format convert v
	11	/ \| ___________/
	12	\| \|/
	13	\| v
	14	\| ___________/\|\___________ _____________
	15	\| / \| \ \| \|
	16	\| Rematrix \| resample <---->\| Buffers \|
	17	\| \___________ \| ___________/ \|_____________\|
	18	v \\|/
	19	Special Converter v
	20	v ___________/\|\___________ _____________
	21	\| / \| \ \| \|
	22	\| Rematrix \| resample <---->\| Buffers \|
	23	\| \___________ \| ___________/ \|_____________\|
	24	\| \\|/
	25	\| v
	26	\| \|\___________
	27	\ \| \
	28	\ output sample format convert v
	29	\_________________ \| ___________/
	30	\\|/
	31	v
	32	Output
	33
	34	Planar/Packed conversion is done when needed during sample format conversion.
	35	Every step can be skipped without memcpy when it is not needed.
	36	Either Resampling and Rematrixing can be performed first depending on which
	37	way it is faster.
	38	The Buffers are needed for resampling due to resamplng being a process that
	39	requires future and past data, it thus also introduces inevitably a delay when
	40	used.
	41	Internally 32bit float and 16bit int is supported currently, other formats can
	42	easily be added.
	43	Externally all sample formats in packed and planar configuration are supported
	44	It's also trivial to add special converters for common cases.
	45	If only sample format and/or packed/planar conversion is needed, it
	46	is performed from input to output directly in a single pass with no intermediates.