output/alsa: drain the whole `ring_buffer`, not just one period

This fixes a problem which caused a failure with snd_pcm_writei() because snd_pcm_drain() had already been called in the previous iteration. This commit makes sure that snd_pcm_drain() is only called after the final snd_pcm_writei() call. This fixes discarded samples at the end of playback.

output/alsa: drain the whole `ring_buffer`, not just one period
436ba3c9 · Max Kellermann · 5d12f528 · 436ba3c9 · 436ba3c9
Commit 436ba3c9 authored Nov 14, 2018 by Max Kellermann
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NEWS NEWS +1 -0

AlsaOutputPlugin.cxx src/output/plugins/AlsaOutputPlugin.cxx +4 -5

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--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ ver 0.21.3 (not yet released)
 * output
  - alsa: fix crash bug
  - alsa: fix stuttering at start of playback
+  - alsa: fix discarded samples at end of song
  - alsa: clear error after reopening device
 * log: default to journal if MPD was started as systemd service

--- a/src/output/plugins/AlsaOutputPlugin.cxx
+++ b/src/output/plugins/AlsaOutputPlugin.cxx
@@ -749,11 +749,10 @@ AlsaOutput::DrainInternal()
 						 snd_strerror(-frames_written));
 		}
-		if (!period_buffer.IsEmpty())
+		/* need to call CopyRingToPeriodBuffer() and
-			/* need to call WriteFromPeriodBuffer() again
+		   WriteFromPeriodBuffer() again in the next
-			   in the next iteration, so don't finish the
+		   iteration, so don't finish the drain just yet */
-			   drain just yet */
+		return period_buffer.IsEmpty();
-			return false;
 	}
 	/* .. and finally drain the ALSA hardware buffer */