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resampler: Resample first followed by remapping if have more out channels than in channels

Browse source 
Reintroduces a cleaned-up version of commit 30ce3a14e5 which
was reverted by 1ce71cbd82; for more information see
http://thread.gmane.org/gmane.comp.audio.pulseaudio.general/17479/focus=17487

The patch intends to reduce computational load when resampling AND remapping. The PA
resampler performs the following steps:

sample format conversion -> remapping -> resampling -> sample format conversion

In case the number of output channels is higher than the number of input channels, the
resampler has to be run more often than necessary. E.g. in case of mono to 4-channel remapping,
the resampler runs on 4 channels separately.

To ímprove this, the PA resampler pipeline is made adaptive:

if out-channels <= in-channels:
  sample format conversion -> remapping -> resampling -> sample format conversion
if out-channels > in-channels:
  sample format conversion -> resampling -> remapping -> sample format conversion

Signed-off-by: Peter Meerwald <p.meerwald@bct-electronic.com>
This commit is contained in:
Peter Meerwald 2013-12-02 17:27:01 +01:00 • committed by Tanu Kaskinen
parent b51d28bbbf
commit 537f430c99
1 changed files with 32 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

44
src/pulsecore/resampler.c
View file

@ -398,12 +398,7 @@ pa_resampler* pa_resampler_new(
calc_map_table(r);
pa_log_info("Using resampler '%s'", pa_resample_method_to_string(method));
r->work_format = pa_resampler_choose_work_format(method, a->format, b->format, r->map_required);
pa_log_info("Using %s as working format.", pa_sample_format_to_string(r->work_format));
r->w_sz = pa_sample_size_of_format(r->work_format);
if (r->i_ss.format != r->work_format) {
@ -428,14 +423,31 @@ pa_resampler* pa_resampler_new(
}
}
/* leftover buffer is the buffer before the resampling stage */
r->leftover_buf = &r->remap_buf;
r->leftover_buf_size = &r->remap_buf_size;
r->have_leftover = &r->leftover_in_remap;
if (r->o_ss.channels <= r->i_ss.channels) {
/* pipeline is: format conv. -> remap -> resample -> format conv. */
r->work_channels = r->o_ss.channels;
r->work_channels = r->o_ss.channels;
/* leftover buffer is remap output buffer (before resampling) */
r->leftover_buf = &r->remap_buf;
r->leftover_buf_size = &r->remap_buf_size;
r->have_leftover = &r->leftover_in_remap;
} else {
/* pipeline is: format conv. -> resample -> remap -> format conv. */
r->work_channels = r->i_ss.channels;
/* leftover buffer is to_work output buffer (before resampling) */
r->leftover_buf = &r->to_work_format_buf;
r->leftover_buf_size = &r->to_work_format_buf_size;
r->have_leftover = &r->leftover_in_to_work;
}
r->w_fz = pa_sample_size_of_format(r->work_format) * r->work_channels;
pa_log_debug("Resampler:");
pa_log_debug(" rate %d -> %d (method %s)", a->rate, b->rate, pa_resample_method_to_string(r->method));
pa_log_debug(" format %s -> %s (intermediate %s)", pa_sample_format_to_string(a->format),
pa_sample_format_to_string(b->format), pa_sample_format_to_string(r->work_format));
pa_log_debug(" channels %d -> %d (resampling %d)", a->channels, b->channels, r->work_channels);
/* initialize implementation */
if (init_table[method](r) < 0)
goto fail;
@ -1348,8 +1360,16 @@ void pa_resampler_run(pa_resampler *r, const pa_memchunk *in, pa_memchunk *out)
buf = (pa_memchunk*) in;
buf = convert_to_work_format(r, buf);
buf = remap_channels(r, buf);
buf = resample(r, buf);
/* Try to save resampling effort: if we have more output channels than
* input channels, do resampling first, then remapping. */
if (r->o_ss.channels <= r->i_ss.channels) {
buf = remap_channels(r, buf);
buf = resample(r, buf);
} else {
buf = resample(r, buf);
buf = remap_channels(r, buf);
}
if (buf->length) {
buf = convert_from_work_format(r, buf);