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csputils: improve contrast semantics for limited range output 

The previous version of this logic resulted in black crush and incorrect
brightness scaling when combined with limited range (TV) output.

(cherry picked from commit 99439f11ea)
This commit is contained in:
Niklas Haas 2015-04-29 22:04:11 +02:00 committed by Diogo Franco (Kovensky)
parent af930e2a2e
commit 99389eb174
1 changed files with 9 additions and 5 deletions
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14
video/csputils.c
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@ -671,18 +671,22 @@ void mp_get_yuv2rgb_coeffs(struct mp_csp_params *params, struct mp_cmat *m)
abort();
}
rgblev.min = (rgblev.min + params->brightness) * params->contrast;
rgblev.max = (rgblev.max + params->brightness) * params->contrast;
double ymul = (rgblev.max - rgblev.min) / (yuvlev.ymax - yuvlev.ymin);
double cmul = (rgblev.max - rgblev.min) / (yuvlev.cmid - yuvlev.cmin) / 2;
// Contrast scales the output value range (gain)
ymul *= params->contrast;
cmul *= params->contrast;
for (int i = 0; i < 3; i++) {
m->m[i][0] *= ymul;
m->m[i][1] *= cmul;
m->m[i][2] *= cmul;
// Set c so that Y=umin,UV=cmid maps to RGB=min (black to black)
// Set c so that Y=umin,UV=cmid maps to RGB=min (black to black),
// also add brightness offset (black lift)
m->c[i] = rgblev.min - m->m[i][0] * yuvlev.ymin
-(m->m[i][1] + m->m[i][2]) * yuvlev.cmid;
- (m->m[i][1] + m->m[i][2]) * yuvlev.cmid
+ params->brightness;
}
int in_bits = FFMAX(params->int_bits_in, 1);