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authorMax Kellermann <max@duempel.org>2014-03-02 11:12:09 +0100
committerMax Kellermann <max@duempel.org>2014-03-02 11:12:25 +0100
commita884e37de16fba2dddbe61e34520860f8b88c15d (patch)
treefe31e7ab622fd132cf3f83052a5c3baa6c6d1c40 /src
parent0102a8665ae23f3e7807f711abbe461e58359f61 (diff)
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output/alsa: call snd_pcm_prepare() after snd_pcm_drop()
Don't wait for an optimistic write to fail. This is an improved workaround for the infamous Raspberry Pi bug (see commit af991765). It works much better and comes without the negative side effects. The old workaround is now obsolete.
Diffstat (limited to 'src')
-rw-r--r--src/output/AlsaOutputPlugin.cxx25
1 files changed, 25 insertions, 0 deletions
diff --git a/src/output/AlsaOutputPlugin.cxx b/src/output/AlsaOutputPlugin.cxx
index 4877d3a46..c5db2320d 100644
--- a/src/output/AlsaOutputPlugin.cxx
+++ b/src/output/AlsaOutputPlugin.cxx
@@ -114,6 +114,18 @@ struct AlsaOutput {
unsigned pi_workaround;
/**
+ * Do we need to call snd_pcm_prepare() before the next write?
+ * It means that we put the device to SND_PCM_STATE_SETUP by
+ * calling snd_pcm_drop().
+ *
+ * Without this flag, we could easily recover after a failed
+ * optimistic write (returning -EBADFD), but the Raspberry Pi
+ * audio driver is infamous for generating ugly artefacts from
+ * this.
+ */
+ bool must_prepare;
+
+ /**
* This buffer gets allocated after opening the ALSA device.
* It contains silence samples, enough to fill one period (see
* #period_frames).
@@ -699,6 +711,8 @@ alsa_open(struct audio_output *ao, AudioFormat &audio_format, Error &error)
ad->in_frame_size = audio_format.GetFrameSize();
ad->out_frame_size = ad->pcm_export->GetFrameSize(audio_format);
+ ad->must_prepare = false;
+
return true;
}
@@ -801,6 +815,7 @@ alsa_cancel(struct audio_output *ao)
AlsaOutput *ad = (AlsaOutput *)ao;
ad->period_position = 0;
+ ad->must_prepare = true;
snd_pcm_drop(ad->pcm);
}
@@ -822,6 +837,16 @@ alsa_play(struct audio_output *ao, const void *chunk, size_t size,
assert(size % ad->in_frame_size == 0);
+ if (ad->must_prepare) {
+ ad->must_prepare = false;
+
+ int err = snd_pcm_prepare(ad->pcm);
+ if (err < 0) {
+ error.Set(alsa_output_domain, err, snd_strerror(-err));
+ return 0;
+ }
+ }
+
chunk = ad->pcm_export->Export(chunk, size, size);
assert(size % ad->out_frame_size == 0);