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From 38cdfa4483de4c2e91bfccb9c22ec72d9c3720f4 Mon Sep 17 00:00:00 2001
From: Walter Lozano <walter.lozano@collabora.com>
Date: Sat, 22 Aug 2020 11:51:30 -0300
Subject: [PATCH 9/9] alsa: adjust delay depending on hardware
Currently PipeWire is able to reproduce audio in systems where
DMA granularity is not burst but it could face an xrun.
In order to mitigate this issue, adjust the delay PipeWire
calculates to make sure that a period is available in the buffer
when snd_pcm_hw_params_is_batch == 1.
Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
---
spa/plugins/alsa/alsa-pcm.c | 12 +++++++++++-
spa/plugins/alsa/alsa-pcm.h | 1 +
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/spa/plugins/alsa/alsa-pcm.c b/spa/plugins/alsa/alsa-pcm.c
index 92ef2151..1f15085f 100644
--- a/spa/plugins/alsa/alsa-pcm.c
+++ b/spa/plugins/alsa/alsa-pcm.c
@@ -462,8 +462,9 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
state->frame_size = info->channels * (snd_pcm_format_physical_width(format) / 8);
dir = 0;
+ state->pcm_is_batch = snd_pcm_hw_params_is_batch(params);
period_size = 1024;
- if (snd_pcm_hw_params_is_batch(params)) {
+ if (state->pcm_is_batch) {
period_size = 512;
spa_log_warn(state->log, NAME" hardware does double buffering, changing period_size to %ld", period_size);
}
@@ -639,6 +640,15 @@ static int get_status(struct state *state, snd_pcm_uframes_t *delay, snd_pcm_ufr
if (state->stream == SND_PCM_STREAM_PLAYBACK) {
*delay = state->buffer_frames - avail;
+ if (state->pcm_is_batch) {
+ /* In this case, as we don't have a good granularity in the
+ * avail report try to compensate this by tweaking the delay
+ * and make sure that a period is available in the buffer */
+ if (*delay > state->period_frames)
+ *delay = *delay - state->period_frames;
+ else
+ *delay = 0;
+ }
}
else {
*delay = avail;
diff --git a/spa/plugins/alsa/alsa-pcm.h b/spa/plugins/alsa/alsa-pcm.h
index b7a2dd29..3b5c0d7b 100644
--- a/spa/plugins/alsa/alsa-pcm.h
+++ b/spa/plugins/alsa/alsa-pcm.h
@@ -100,6 +100,7 @@ struct state {
bool have_format;
struct spa_audio_info current_format;
+ bool pcm_is_batch;
snd_pcm_uframes_t buffer_frames;
snd_pcm_uframes_t period_frames;
--
2.20.1
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