From: Timo Wischer <twischer@xxxxxxxxxxxxxx>
Distorted sound is heard if the capture device of an ioplug plugin is used,
which is accessed through any ALSA plugin (like copy, linear, ...) via MMAP access.
E.g. aplay -> loop -> copy -> arecord -M -> aplay -> hw:0
As mentioned in the ALSA API (see pcm/pcm.c:942):
The function #snd_pcm_avail_update() have to be called
before any mmap begin+commit operation.
Signed-off-by: Timo Wischer <twischer@xxxxxxxxxxxxxx>
Signed-off-by: Mounesh Sutar <sutar.mounesh@xxxxxxxxx>
diff --git a/src/pcm/pcm_plugin.c b/src/pcm/pcm_plugin.c
index aaea2ab..ec57f6e 100644
--- a/src/pcm/pcm_plugin.c
+++ b/src/pcm/pcm_plugin.c
@@ -490,7 +490,14 @@ static snd_pcm_sframes_t snd_pcm_plugin_avail_update(snd_pcm_t *pcm)
snd_pcm_uframes_t slave_offset;
snd_pcm_uframes_t slave_frames = ULONG_MAX;
snd_pcm_sframes_t result;
-
+ /* As mentioned in the ALSA API (see pcm/pcm.c:942):
+ * The function #snd_pcm_avail_update()
+ * have to be called before any mmap begin+commit operation.
+ * Otherwise the snd_pcm_areas_copy will not called a second time.
+ * But this is needed, if the ring buffer wrap is reached and
+ * there is more data available.
+ */
+ slave_size = snd_pcm_avail_update(slave);
result = snd_pcm_mmap_begin(slave, &slave_areas, &slave_offset, &slave_frames);
if (result < 0) {
err = result;
--
2.7.4
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