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Optimization to latest aac decoder changes. Significantly reduce loop count in m4a_check_sample_offset() during standard playback. Before this change the loop count increased with each decoded chunk and for each frame.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29750 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andree Buschmann 2011-04-19 05:55:54 +00:00
parent 8d1d2f8982
commit 2358fabb70
3 changed files with 14 additions and 7 deletions
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11
apps/codecs/libm4a/m4a.c
View file

@ -124,10 +124,14 @@ void stream_create(stream_t *stream,struct codec_api* ci)
/* Check if there is a dedicated byte position contained for the given frame.
* Return this byte position in case of success or return -1. This allows to
* skip empty samples. */
int m4a_check_sample_offset(demux_res_t *demux_res, uint32_t frame)
* skip empty samples.
* During standard playback the search result (index i) will always increase.
* Therefor we save this index and let the caller set this value again as start
* index when calling m4a_check_sample_offset() for the next frame. This
* reduces the overall loop count significantly. */
int m4a_check_sample_offset(demux_res_t *demux_res, uint32_t frame, uint32_t *start)
{
uint32_t i = 0;
uint32_t i = *start;
for (i=0; i<demux_res->num_lookup_table; ++i)
{
if (demux_res->lookup_table[i].sample > frame ||
@ -136,6 +140,7 @@ int m4a_check_sample_offset(demux_res_t *demux_res, uint32_t frame)
if (demux_res->lookup_table[i].sample == frame)
break;
}
*start = i;
return demux_res->lookup_table[i].offset;
}

2
apps/codecs/libm4a/m4a.h
View file

@ -137,6 +137,6 @@ unsigned int m4a_seek (demux_res_t* demux_res, stream_t* stream,
int* current_sample);
unsigned int m4a_seek_raw (demux_res_t* demux_res, stream_t* stream,
uint32_t file_loc, uint32_t* sound_samples_done, int* current_sample);
int m4a_check_sample_offset(demux_res_t *demux_res, uint32_t frame);
int m4a_check_sample_offset(demux_res_t *demux_res, uint32_t frame, uint32_t *start);
#endif /* STREAM_H */