[FFmpeg-cvslog] lavfi/overlay: enable yuva420p as overlay background
Mark Himsley
git at videolan.org
Tue Nov 27 10:48:10 CET 2012
ffmpeg | branch: master | Mark Himsley <mark at mdsh.com> | Sun Nov 25 15:24:29 2012 +0000| [13c62525362595cc914161aaa192953dd9077233] | committer: Stefano Sabatini
lavfi/overlay: enable yuva420p as overlay background
Same calculation as for RGBA etc to create unpremultiplied output.
Useful for creating an intermediate "Mix/Effects bank", in vision mixer
(switcher) terminology.
Example command:
ffmpeg -i input.mov -vf
"[in]scale=iw:ih:interl=1,format=yuv420p[bg];movie=BBC_blocks_watermark.png,scale=iw:ih:interl=1,format=yuva420p[dog];movie=Kickabout_strap.mov,scale=iw:ih:interl=1,format=yuva420p[strap];[strap][dog]overlay=0:0[me1];[bg][me1]overlay=0:0,scale=0:0:interl=1[out]"
-b:v 3M -an output.mov
Fix trac ticket #549.
Signed-off-by: Stefano Sabatini <stefasab at gmail.com>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=13c62525362595cc914161aaa192953dd9077233
---
libavfilter/version.h | 2 +-
libavfilter/vf_overlay.c | 70 +++++++++++++++++++++++++++++++++++++++-------
2 files changed, 61 insertions(+), 11 deletions(-)
diff --git a/libavfilter/version.h b/libavfilter/version.h
index 04d6fa1..04ab662 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -30,7 +30,7 @@
#define LIBAVFILTER_VERSION_MAJOR 3
#define LIBAVFILTER_VERSION_MINOR 23
-#define LIBAVFILTER_VERSION_MICRO 102
+#define LIBAVFILTER_VERSION_MICRO 103
#define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
LIBAVFILTER_VERSION_MINOR, \
diff --git a/libavfilter/vf_overlay.c b/libavfilter/vf_overlay.c
index f060684..d61d18e 100644
--- a/libavfilter/vf_overlay.c
+++ b/libavfilter/vf_overlay.c
@@ -157,7 +157,7 @@ static int query_formats(AVFilterContext *ctx)
OverlayContext *over = ctx->priv;
/* overlay formats contains alpha, for avoiding conversion with alpha information loss */
- const enum AVPixelFormat main_pix_fmts_yuv[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
+ const enum AVPixelFormat main_pix_fmts_yuv[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVA420P, AV_PIX_FMT_NONE };
const enum AVPixelFormat overlay_pix_fmts_yuv[] = { AV_PIX_FMT_YUVA420P, AV_PIX_FMT_NONE };
const enum AVPixelFormat main_pix_fmts_rgb[] = {
AV_PIX_FMT_ARGB, AV_PIX_FMT_RGBA,
@@ -293,6 +293,12 @@ static AVFilterBufferRef *get_video_buffer(AVFilterLink *link, int perms, int w,
// apply a fast variant: (X+127)/255 = ((X+127)*257+257)>>16 = ((X+128)*257)>>16
#define FAST_DIV255(x) ((((x) + 128) * 257) >> 16)
+// calculate the unpremultiplied alpha, applying the general equation:
+// alpha = alpha_overlay / ( (alpha_main + alpha_overlay) - (alpha_main * alpha_overlay) )
+// (((x) << 16) - ((x) << 9) + (x)) is a faster version of: 255 * 255 * x
+// ((((x) + (y)) << 8) - ((x) + (y)) - (y) * (x)) is a faster version of: 255 * (x + y)
+#define UNPREMULTIPLY_ALPHA(x, y) ((((x) << 16) - ((x) << 9) + (x)) / ((((x) + (y)) << 8) - ((x) + (y)) - (y) * (x)))
+
static void blend_slice(AVFilterContext *ctx,
AVFilterBufferRef *dst, AVFilterBufferRef *src,
int x, int y, int w, int h,
@@ -336,15 +342,8 @@ static void blend_slice(AVFilterContext *ctx,
// if the main channel has an alpha channel, alpha has to be calculated
// to create an un-premultiplied (straight) alpha value
if (main_has_alpha && alpha != 0 && alpha != 255) {
- // apply the general equation:
- // alpha = alpha_overlay / ( (alpha_main + alpha_overlay) - (alpha_main * alpha_overlay) )
- alpha =
- // the next line is a faster version of: 255 * 255 * alpha
- ( (alpha << 16) - (alpha << 9) + alpha )
- /
- // the next line is a faster version of: 255 * (alpha + d[da])
- ( ((alpha + d[da]) << 8 ) - (alpha + d[da])
- - d[da] * alpha );
+ uint8_t alpha_d = d[da];
+ alpha = UNPREMULTIPLY_ALPHA(alpha, alpha_d);
}
switch (alpha) {
@@ -381,6 +380,39 @@ static void blend_slice(AVFilterContext *ctx,
sp += src->linesize[0];
}
} else {
+ const int main_has_alpha = over->main_has_alpha;
+ if (main_has_alpha) {
+ uint8_t *da = dst->data[3] + x * over->main_pix_step[3] +
+ start_y * dst->linesize[3];
+ uint8_t *sa = src->data[3];
+ uint8_t alpha; ///< the amount of overlay to blend on to main
+ if (slice_y > y)
+ sa += (slice_y - y) * src->linesize[3];
+ for (i = 0; i < height; i++) {
+ uint8_t *d = da, *s = sa;
+ for (j = 0; j < width; j++) {
+ alpha = *s;
+ if (alpha != 0 && alpha != 255) {
+ uint8_t alpha_d = *d;
+ alpha = UNPREMULTIPLY_ALPHA(alpha, alpha_d);
+ }
+ switch (alpha) {
+ case 0:
+ break;
+ case 255:
+ *d = *s;
+ break;
+ default:
+ // apply alpha compositing: main_alpha += (1-main_alpha) * overlay_alpha
+ *d += FAST_DIV255((255 - *d) * *s);
+ }
+ d += 1;
+ s += 1;
+ }
+ da += dst->linesize[3];
+ sa += src->linesize[3];
+ }
+ }
for (i = 0; i < 3; i++) {
int hsub = i ? over->hsub : 0;
int vsub = i ? over->vsub : 0;
@@ -410,6 +442,24 @@ static void blend_slice(AVFilterContext *ctx,
alpha = (alpha_v + alpha_h) >> 1;
} else
alpha = a[0];
+ // if the main channel has an alpha channel, alpha has to be calculated
+ // to create an un-premultiplied (straight) alpha value
+ if (main_has_alpha && alpha != 0 && alpha != 255) {
+ // average alpha for color components, improve quality
+ uint8_t alpha_d;
+ if (hsub && vsub && j+1 < hp && k+1 < wp) {
+ alpha_d = (d[0] + d[src->linesize[3]] +
+ d[1] + d[src->linesize[3]+1]) >> 2;
+ } else if (hsub || vsub) {
+ alpha_h = hsub && k+1 < wp ?
+ (d[0] + d[1]) >> 1 : d[0];
+ alpha_v = vsub && j+1 < hp ?
+ (d[0] + d[src->linesize[3]]) >> 1 : d[0];
+ alpha_d = (alpha_v + alpha_h) >> 1;
+ } else
+ alpha_d = d[0];
+ alpha = UNPREMULTIPLY_ALPHA(alpha, alpha_d);
+ }
*d = FAST_DIV255(*d * (255 - alpha) + *s * alpha);
s++;
d++;
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