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swscale: document SWS_FULL_CHR_H_* flags 

Based on my best understanding of what they do, given the source code.
This commit is contained in:
Niklas Haas 2024-07-04 12:44:20 +02:00
parent be7ab63552
commit 3e064f52eb
1 changed files with 26 additions and 2 deletions
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28
libswscale/swscale.h
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@ -82,11 +82,35 @@ const char *swscale_license(void);
#define SWS_PRINT_INFO 0x1000
//the following 3 flags are not completely implemented
//internal chrominance subsampling info
/**
* Perform full chroma upsampling when upscaling to RGB.
*
* For example, when converting 50x50 yuv420p to 100x100 rgba, setting this flag
* will scale the chroma plane from 25x25 to 100x100 (4:4:4), and then convert
* the 100x100 yuv444p image to rgba in the final output step.
*
* Without this flag, the chroma plane is instead scaled to 50x100 (4:2:2),
* with a single chroma sample being re-used for both of the horizontally
* adjacent RGBA output pixels.
*/
#define SWS_FULL_CHR_H_INT 0x2000
//input subsampling info
/**
* Perform full chroma interpolation when downscaling RGB sources.
*
* For example, when converting a 100x100 rgba source to 50x50 yuv444p, setting
* this flag will generate a 100x100 (4:4:4) chroma plane, which is then
* downscaled to the required 50x50.
*
* Without this flag, the chroma plane is instead generated at 50x100 (dropping
* every other pixel), before then being downscaled to the required 50x50
* resolution.
*/
#define SWS_FULL_CHR_H_INP 0x4000
#define SWS_DIRECT_BGR 0x8000
#define SWS_ACCURATE_RND 0x40000
#define SWS_BITEXACT 0x80000
#define SWS_ERROR_DIFFUSION 0x800000