Changes in v3:
Dropped useless reverse endian code
Changes in v2:
* DSD support
* Cleanup
"MPD doesn't support the other pulseaudio sample formats, so
we just force MPD to send us everything as 16 bit"
At some point the comment was probably true, but recent
versions of pulseaudio have no trouble with any reasonable
selection of sample formats.
There are some exceptions:
* at present DSD is not (yet) supported in pulseaudio, so
in the meantime DSD is supported by downsampling to
a decent PCM spec
* pulseaudio supports U8, but not S8, vis-versa for mpd
* pulseaudio supports both packed and unpacked variants of
S24 for both endian, but mpd apparently doesn't support
non-packed 24bit samples, which is a little odd since the
ALSA output plugin assumes it does and so seems to always
fall back to packed for 24bit formats!?! (bug?)
I originally started this patch from the multi-format support
code in the ALSA plugin, and as such it still contains the
logic for fall-back formats, but whereas the ALSA plugin
attempts to open a stream, this isn't necessary in this case
since there's a pulse API for testing the validity of a
sample_spec.
---
src/output/plugins/PulseOutputPlugin.cxx | 91 +++++++++++++++++++++++++++++---
1 file changed, 85 insertions(+), 6 deletions(-)
diff --git a/src/output/plugins/PulseOutputPlugin.cxx
b/src/output/plugins/PulseOutputPlugin.cxx
index 0d79af7..30ab396 100644
--- a/src/output/plugins/PulseOutputPlugin.cxx
+++ b/src/output/plugins/PulseOutputPlugin.cxx
@@ -544,6 +544,54 @@ pulse_output_setup_stream(PulseOutput *po, const
pa_sample_spec *ss,
return true;
}
+static pa_sample_format_t
+get_bitformat(SampleFormat sample_format)
+{
+ /* Pulse supports U8 and S24LE/BE formats but mpd
+ currently does not. Pulse does not support S8. */
+ switch (sample_format) {
+ case SampleFormat::UNDEFINED:
+ case SampleFormat::DSD:
+ case SampleFormat::S8:
+ return PA_SAMPLE_INVALID;
+
+ case SampleFormat::S16:
+ return PA_SAMPLE_S16NE;
+
+ case SampleFormat::S24_P32:
+ return PA_SAMPLE_S24_32NE;
+
+ case SampleFormat::S32:
+ return PA_SAMPLE_S32NE;
+
+ case SampleFormat::FLOAT:
+ return PA_SAMPLE_FLOAT32NE;
+ }
+
+ assert(false);
+ gcc_unreachable();
+}
+
+static pa_sample_spec
+pulse_get_valid_spec(uint32_t sample_rate, SampleFormat sample_format,
+ uint8_t channels)
+{
+ pa_sample_spec test_spec;
+ int ret;
+
+ test_spec.format = get_bitformat(sample_format);
+ test_spec.rate = sample_rate;
+ test_spec.channels = channels;
+ if (test_spec.format == PA_SAMPLE_INVALID)
+ return test_spec;
+
+ ret = pa_sample_spec_valid(&test_spec);
+ if (ret == 0)
+ test_spec.format = PA_SAMPLE_INVALID;
+
+ return test_spec;
+}
+
static bool
pulse_output_open(AudioOutput *ao, AudioFormat &audio_format,
Error &error)
@@ -579,13 +627,44 @@ pulse_output_open(AudioOutput *ao, AudioFormat
&audio_format,
return false;
}
- /* MPD doesn't support the other pulseaudio sample formats, so
- we just force MPD to send us everything as 16 bit */
- audio_format.format = SampleFormat::S16;
+ /* pulseaudio can validate a sample_spec before opening the stream */
+
+ ss = pulse_get_valid_spec(audio_format.sample_rate,
+ audio_format.format, audio_format.channels);
- ss.format = PA_SAMPLE_S16NE;
- ss.rate = audio_format.sample_rate;
- ss.channels = audio_format.channels;
+ /* if unsupported, try other formats */
+
+ if (ss.format == PA_SAMPLE_INVALID) {
+ /* Pulse doesn't yet support DSD so attempt to resample
+ to high quality PCM - maybe higher would be better,
+ but that would then typically need to be resampled
+ twice! :-/ */
+ if (audio_format.format == SampleFormat::DSD)
+ {
+ audio_format.format = SampleFormat::FLOAT;
+ audio_format.sample_rate = 48000;
+ }
+
+ static const SampleFormat probe_formats[] = {
+ SampleFormat::S32,
+ SampleFormat::S24_P32,
+ SampleFormat::S16,
+ SampleFormat::UNDEFINED,
+ };
+
+ for (unsigned i = 0;
+ ss.format == PA_SAMPLE_INVALID && probe_formats[i] !=
SampleFormat::UNDEFINED;
+ ++i) {
+ const SampleFormat mpd_format = probe_formats[i];
+ if (mpd_format == audio_format.format)
+ continue;
+
+ ss = pulse_get_valid_spec(audio_format.sample_rate,
+ mpd_format, audio_format.channels);
+ if (ss.format != PA_SAMPLE_INVALID)
+ audio_format.format = mpd_format;
+ }
+ }
/* create a stream .. */
--
2.1.0
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