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Greatly reduce volume-change zipper artifacts with SW volume.

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Uses a cosine factor to smoothly shift the PCM level from the old level
to the new one over the length of a frame.

Implements indirect calls to PCM scaling function instead of testing
conditions on every callback, cleanly assigning a different call to
do the volume transition. The volume change call then assigns the final
scaling function.

Change-Id: If1004b92a91c5ca766dd0e4014ec274636e8ed26
Reviewed-on: http://gerrit.rockbox.org/763
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested: Michael Sevakis <jethead71@rockbox.org>
This commit is contained in:
Michael Sevakis 2013-08-23 14:18:08 -04:00
parent 62b10e383c
commit 61d0583384
3 changed files with 108 additions and 28 deletions
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firmware/export/pcm-internal.h
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@ -57,6 +57,7 @@ void pcm_sw_volume_copy_buffer(void *dst, const void *src, size_t size);
#endif
#endif /* PCM_SW_VOLUME_UNBUFFERED */
void pcm_sync_pcm_factors(void);
#endif /* HAVE_SW_VOLUME_CONTROL */
#define PCM_SAMPLE_SIZE (2 * sizeof (int16_t))