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Code Issues Releases Activity

adpcm: Use a hash table to improve checking for duplicate samples

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This lowers the run time from 158 to 21 seconds, for -trellis 8
with a 30 second sample on my machine.

This requires 64 KB additional memory.

Originally committed as revision 25768 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Martin Storsjö 2010-11-19 17:35:52 +00:00
parent 47d2ddca80
commit d764e3ece9
1 changed files with 27 additions and 8 deletions
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33
libavcodec/adpcm.c
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@ -163,6 +163,7 @@ typedef struct ADPCMContext {
TrellisPath *paths;
TrellisNode *node_buf;
TrellisNode **nodep_buf;
uint8_t *trellis_hash;
} ADPCMContext;
#define FREEZE_INTERVAL 128
@ -189,6 +190,7 @@ static av_cold int adpcm_encode_init(AVCodecContext *avctx)
FF_ALLOC_OR_GOTO(avctx, s->paths, max_paths * sizeof(*s->paths), error);
FF_ALLOC_OR_GOTO(avctx, s->node_buf, 2 * frontier * sizeof(*s->node_buf), error);
FF_ALLOC_OR_GOTO(avctx, s->nodep_buf, 2 * frontier * sizeof(*s->nodep_buf), error);
FF_ALLOC_OR_GOTO(avctx, s->trellis_hash, 65536 * sizeof(*s->trellis_hash), error);
}
switch(avctx->codec->id) {
@ -242,6 +244,7 @@ error:
av_freep(&s->paths);
av_freep(&s->node_buf);
av_freep(&s->nodep_buf);
av_freep(&s->trellis_hash);
return -1;
}
@ -252,6 +255,7 @@ static av_cold int adpcm_encode_close(AVCodecContext *avctx)
av_freep(&s->paths);
av_freep(&s->node_buf);
av_freep(&s->nodep_buf);
av_freep(&s->trellis_hash);
return 0;
}
@ -325,7 +329,9 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
TrellisNode **nodep_buf = s->nodep_buf;
TrellisNode **nodes = nodep_buf; // nodes[] is always sorted by .ssd
TrellisNode **nodes_next = nodep_buf + frontier;
int pathn = 0, froze = -1, i, j, k;
int pathn = 0, froze = -1, i, j, k, generation = 0;
uint8_t *hash = s->trellis_hash;
memset(hash, 0xff, 65536 * sizeof(*hash));
memset(nodep_buf, 0, 2 * frontier * sizeof(*nodep_buf));
nodes[0] = node_buf + frontier;
@ -372,18 +378,24 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
uint32_t ssd;\
int pos;\
TrellisNode *u;\
uint8_t *h;\
dec_sample = av_clip_int16(dec_sample);\
d = sample - dec_sample;\
ssd = nodes[j]->ssd + d*d;\
/* Collapse any two states with the same previous sample value. \
* One could also distinguish states by step and by 2nd to last
* sample, but the effects of that are negligible. */\
for(k=0; k<frontier && nodes_next[k]; k++) {\
if(dec_sample == nodes_next[k]->sample1) {\
assert(ssd >= nodes_next[k]->ssd);\
* sample, but the effects of that are negligible.
* Since nodes in the previous generation are iterated
* through a heap, they're roughly ordered from better to
* worse, but not strictly ordered. Therefore, an earlier
* node with the same sample value is better in most cases
* (and thus the current is skipped), but not strictly
* in all cases. Only skipping samples where ssd >=
* ssd of the earlier node with the same sample gives
* slightly worse quality, though, for some reason. */ \
h = &hash[(uint16_t) dec_sample];\
if (*h == generation)\
goto next_##NAME;\
}\
}\
if (heap_pos < frontier) {\
pos = heap_pos++;\
} else {\
@ -393,6 +405,7 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
if (ssd > nodes_next[pos]->ssd)\
goto next_##NAME;\
}\
*h = generation;\
u = nodes_next[pos];\
if(!u) {\
assert(pathn < FREEZE_INTERVAL<<avctx->trellis);\
@ -443,6 +456,12 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
nodes = nodes_next;
nodes_next = u;
generation++;
if (generation == 255) {
memset(hash, 0xff, 65536 * sizeof(*hash));
generation = 0;
}
// prevent overflow
if(nodes[0]->ssd > (1<<28)) {
for(j=1; j<frontier && nodes[j]; j++)