Hi,
On Wed, Apr 20, 2011 at 3:45 PM, Anton Khirnov <an...@khirnov.net> wrote:
> From: Michael Niedermayer <michae...@gmx.at>
>
> Signed-off-by: Michael Niedermayer <michae...@gmx.at>
> Signed-off-by: Anton Khirnov <an...@khirnov.net>
> ---
> libavfilter/vf_drawtext.c | 10 ++++++----
> 1 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
> index fa6b7fd..7b503f5 100644
> --- a/libavfilter/vf_drawtext.c
> +++ b/libavfilter/vf_drawtext.c
> @@ -385,12 +385,14 @@ static int config_input(AVFilterLink *inlink)
>
> #define SET_PIXEL_YUV(picref, yuva_color, val, x, y, hsub, vsub) {
> \
> luma_pos = ((x) ) + ((y) ) * picref->linesize[0]; \
> - chroma_pos1 = ((x) >> (hsub)) + ((y) >> (vsub)) * picref->linesize[1]; \
> - chroma_pos2 = ((x) >> (hsub)) + ((y) >> (vsub)) * picref->linesize[2]; \
> alpha = yuva_color[3] * (val) * 129; \
> picref->data[0][luma_pos] = (alpha * yuva_color[0] + (255*255*129 -
> alpha) * picref->data[0][luma_pos] ) >> 23; \
> - picref->data[1][chroma_pos1] = (alpha * yuva_color[1] + (255*255*129 -
> alpha) * picref->data[1][chroma_pos1]) >> 23; \
> - picref->data[2][chroma_pos2] = (alpha * yuva_color[2] + (255*255*129 -
> alpha) * picref->data[2][chroma_pos2]) >> 23; \
> + if(((x) & ((1<<(hsub))-1))==0 && ((y) & ((1<<(vsub))-1))==0){\
> + chroma_pos1 = ((x) >> (hsub)) + ((y) >> (vsub)) *
> picref->linesize[1]; \
> + chroma_pos2 = ((x) >> (hsub)) + ((y) >> (vsub)) *
> picref->linesize[2]; \
> + picref->data[1][chroma_pos1] = (alpha * yuva_color[1] + (255*255*129
> - alpha) * picref->data[1][chroma_pos1]) >> 23; \
> + picref->data[2][chroma_pos2] = (alpha * yuva_color[2] + (255*255*129
> - alpha) * picref->data[2][chroma_pos2]) >> 23; \
> + }\
This patch may optimize, but the big issue is that it loses 3/4 of
chroma information when drawing the U/V planes in 420P. That may be
optimal performance-wise, but isn't a great idea quality-wise.
Ronald
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