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Code Issues Releases Activity

avcodec/dvbsubdec: Compute scoretab without iterating over pixels multiple times in compute_default_clut()

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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@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2018-06-21 23:32:23 +02:00
parent b31189881a
commit 71ba79702d
1 changed files with 25 additions and 19 deletions
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44
libavcodec/dvbsubdec.c
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@ -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;
}