avformat/hlsenc: add option hls_delete_threshold
[ffmpeg.git] / doc / swresample.txt
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.