[FFmpeg-cvslog] avcodec/dvbsubdec: Compute scoretab without iterating over pixels multiple times in compute_default_clut()
Michael Niedermayer
git at videolan.org
Wed Jun 27 14:51:51 EEST 2018
ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Jun 21 23:32:23 2018 +0200| [71ba79702d3330c2aff66434e9fbe515c8f44a6b] | committer: Michael Niedermayer
avcodec/dvbsubdec: Compute scoretab without iterating over pixels multiple times in compute_default_clut()
Improves speed 102->2 sec
Testcase: 8655/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DVBSUB_fuzzer-6277869285146624
Fixes: Timeout
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=71ba79702d3330c2aff66434e9fbe515c8f44a6b
---
libavcodec/dvbsubdec.c | 44 +++++++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 19 deletions(-)
diff --git a/libavcodec/dvbsubdec.c b/libavcodec/dvbsubdec.c
index a657b1d3d0..b59e836657 100644
--- a/libavcodec/dvbsubdec.c
+++ b/libavcodec/dvbsubdec.c
@@ -127,6 +127,7 @@ typedef struct DVBSubContext {
int compute_edt; /**< if 1 end display time calculated using pts
if 0 (Default) calculated using time out */
int compute_clut;
+ int clut_count2[257][256];
int substream;
int64_t prev_start;
DVBSubRegion *region_list;
@@ -650,13 +651,17 @@ static int dvbsub_read_8bit_string(AVCodecContext *avctx,
return pixels_read;
}
-static void compute_default_clut(uint8_t *clut, AVSubtitleRect *rect, int w, int h)
+static void compute_default_clut(DVBSubContext *ctx, uint8_t *clut, AVSubtitleRect *rect, int w, int h)
{
uint8_t list[256] = {0};
uint8_t list_inv[256];
int counttab[256] = {0};
+ int (*counttab2)[256] = ctx->clut_count2;
int count, i, x, y;
ptrdiff_t stride = rect->linesize[0];
+
+ memset(ctx->clut_count2, 0 , sizeof(ctx->clut_count2));
+
#define V(x,y) rect->data[0][(x) + (y)*stride]
for (y = 0; y<h; y++) {
for (x = 0; x<w; x++) {
@@ -666,31 +671,32 @@ static void compute_default_clut(uint8_t *clut, AVSubtitleRect *rect, int w, int
int vt = y ? V(x,y-1) + 1 : 0;
int vb = y+1<h ? V(x,y+1) + 1 : 0;
counttab[v-1] += !!((v!=vl) + (v!=vr) + (v!=vt) + (v!=vb));
+ counttab2[vl][v-1] ++;
+ counttab2[vr][v-1] ++;
+ counttab2[vt][v-1] ++;
+ counttab2[vb][v-1] ++;
}
}
#define L(x,y) list[d[(x) + (y)*stride]]
for (i = 0; i<256; i++) {
- int scoretab[256] = {0};
+ counttab2[i+1][i] = 0;
+ }
+ for (i = 0; i<256; i++) {
int bestscore = 0;
int bestv = 0;
- for (y = 0; y<h; y++) {
- for (x = 0; x<w; x++) {
- uint8_t *d = &rect->data[0][x + y*stride];
- int v = *d;
- int l_m = list[v];
- int l_l = x ? L(-1, 0) : 1;
- int l_r = x+1<w ? L( 1, 0) : 1;
- int l_t = y ? L( 0,-1) : 1;
- int l_b = y+1<h ? L( 0, 1) : 1;
- if (l_m)
- continue;
- scoretab[v] += l_l + l_r + l_t + l_b;
- }
- }
+
for (x = 0; x < 256; x++) {
- if (scoretab[x]) {
- int score = 1024LL*scoretab[x] / counttab[x];
+ int scorev = 0;
+ if (list[x])
+ continue;
+ scorev += counttab2[0][x];
+ for (y = 0; y < 256; y++) {
+ scorev += list[y] * counttab2[y+1][x];
+ }
+
+ if (scorev) {
+ int score = 1024LL*scorev / counttab[x];
if (score > bestscore) {
bestscore = score;
bestv = x;
@@ -819,7 +825,7 @@ static int save_subtitle_set(AVCodecContext *avctx, AVSubtitle *sub, int *got_ou
if ((clut == &default_clut && ctx->compute_clut == -1) || ctx->compute_clut == 1) {
if (!region->has_computed_clut) {
- compute_default_clut(region->computed_clut, rect, rect->w, rect->h);
+ compute_default_clut(ctx, region->computed_clut, rect, rect->w, rect->h);
region->has_computed_clut = 1;
}
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