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Code Issues Releases Activity

adpcm: Store the trellis nodes in a heap instead of a sorted array

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This avoids having to memmove the large parts of the array when inserting into
it.

For -trellis 8, this lowers the run time from 245 seconds to 190 seconds,
for a 30 second 44 kHz mono sample, on my machine.

Originally committed as revision 25731 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Martin Storsjö 2010-11-12 12:27:27 +00:00
parent 5d6e4c160a
commit f82e8f3482
1 changed files with 29 additions and 8 deletions
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37
libavcodec/adpcm.c
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@ -352,6 +352,7 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
TrellisNode *t = node_buf + frontier*(i&1);
TrellisNode **u;
int sample = samples[i*stride];
int heap_pos = 0;
memset(nodes_next, 0, frontier*sizeof(TrellisNode*));
for(j=0; j<frontier && nodes[j]; j++) {
// higher j have higher ssd already, so they're unlikely to use a suboptimal next sample too
@ -369,11 +370,11 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
#define STORE_NODE(NAME, STEP_INDEX)\
int d;\
uint32_t ssd;\
int pos;\
TrellisNode *u;\
dec_sample = av_clip_int16(dec_sample);\
d = sample - dec_sample;\
ssd = nodes[j]->ssd + d*d;\
if(nodes_next[frontier-1] && ssd >= nodes_next[frontier-1]->ssd)\
continue;\
/* 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. */\
@ -383,12 +384,28 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
goto next_##NAME;\
}\
}\
for(k=0; k<frontier; k++) {\
if(!nodes_next[k] || ssd < nodes_next[k]->ssd) {\
TrellisNode *u = nodes_next[frontier-1];\
if (heap_pos < frontier) {\
pos = heap_pos++;\
} else {\
/* Find the largest node in the heap, which is one \
* of the leaf nodes. */\
int maxpos = 0;\
uint32_t max_ssd = 0;\
for (k = frontier >> 1; k < frontier; k++) {\
if (nodes_next[k]->ssd > max_ssd) {\
maxpos = k;\
max_ssd = nodes_next[k]->ssd;\
}\
}\
pos = maxpos;\
if (ssd > max_ssd)\
goto next_##NAME;\
}\
u = nodes_next[pos];\
if(!u) {\
assert(pathn < FREEZE_INTERVAL<<avctx->trellis);\
u = t++;\
nodes_next[pos] = u;\
u->path = pathn++;\
}\
u->ssd = ssd;\
@ -397,10 +414,14 @@ static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
u->sample1 = dec_sample;\
paths[u->path].nibble = nibble;\
paths[u->path].prev = nodes[j]->path;\
memmove(&nodes_next[k+1], &nodes_next[k], (frontier-k-1)*sizeof(TrellisNode*));\
nodes_next[k] = u;\
/* Sift the newly inserted node down in the heap to \
* restore the heap property. */\
while (pos > 0) {\
int parent = (pos - 1) >> 1;\
if (nodes_next[parent]->ssd <= ssd)\
break;\
}\
FFSWAP(TrellisNode*, nodes_next[parent], nodes_next[pos]);\
pos = parent;\
}\
next_##NAME:;
STORE_NODE(ms, FFMAX(16, (AdaptationTable[nibble] * step) >> 8));