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cljrenc: Add dither to avoid the banding artifcats caused by the very low

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number of bits used to represent brightness levels.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2011-12-09 01:11:06 +01:00
parent 25b9eef410
commit 43a36ad2ee
1 changed files with 8 additions and 6 deletions
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14
libavcodec/cljr.c
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@ -132,6 +132,7 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf,
PutBitContext pb; PutBitContext pb;
AVFrame *p = data; AVFrame *p = data;
int x, y; int x, y;
uint32_t dither= avctx->frame_number;
p->pict_type = AV_PICTURE_TYPE_I; p->pict_type = AV_PICTURE_TYPE_I;
p->key_frame = 1; p->key_frame = 1;
@ -143,13 +144,14 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf,
uint8_t *cb = &p->data[1][y * p->linesize[1]]; uint8_t *cb = &p->data[1][y * p->linesize[1]];
uint8_t *cr = &p->data[2][y * p->linesize[2]]; uint8_t *cr = &p->data[2][y * p->linesize[2]];
for (x = 0; x < avctx->width; x += 4) { for (x = 0; x < avctx->width; x += 4) {
put_bits(&pb, 5, luma[3] >> 3); put_bits(&pb, 5, (luma[3] + (dither>>29) ) >> 3);
put_bits(&pb, 5, luma[2] >> 3); put_bits(&pb, 5, (luma[2] + ((dither>>26)&7)) >> 3);
put_bits(&pb, 5, luma[1] >> 3); put_bits(&pb, 5, (luma[1] + ((dither>>23)&7)) >> 3);
put_bits(&pb, 5, luma[0] >> 3); put_bits(&pb, 5, (luma[0] + ((dither>>20)&7)) >> 3);
luma += 4; luma += 4;
put_bits(&pb, 6, *(cb++) >> 2); put_bits(&pb, 6, (*(cb++) + ((dither>>18)&3)) >> 2);
put_bits(&pb, 6, *(cr++) >> 2); put_bits(&pb, 6, (*(cr++) + ((dither>>16)&3)) >> 2);
dither = dither*1664525+1013904223;
} }
} }