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alsa: correct dll error after quantum change

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When the quantum is changed, the error between the current and
expected buffer levels needs to be corrected with the quantum
difference.

For example, say we are running with a 1024 quantum and the quantum
is changed to 8192, when we wake up the filled level might be
1016 vs expected 8192, 1024 - 8192 = -7168. The real error for the
timeout was 1016 - 8192 - (-7168) = -8.
This commit is contained in:
Wim Taymans 2021-03-08 16:12:35 +01:00
parent ffeb2e0f0e
commit 2c1f8af2e6
1 changed files with 11 additions and 9 deletions
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20
spa/plugins/alsa/alsa-pcm.c
View file

@ -856,29 +856,31 @@ static int update_time(struct state *state, uint64_t nsec, snd_pcm_sframes_t del
snd_pcm_sframes_t target, bool follower)
{
double err, corr;
int32_t diff;
if (state->stream == SND_PCM_STREAM_PLAYBACK)
err = delay - target;
else
err = target - delay;
err = SPA_CLAMP(err, -state->max_error, state->max_error);
if (SPA_UNLIKELY(state->dll.bw == 0.0)) {
spa_dll_set_bw(&state->dll, SPA_DLL_BW_MAX, state->threshold, state->rate);
state->next_time = nsec;
state->base_time = nsec;
}
corr = spa_dll_update(&state->dll, err);
diff = (int32_t) (state->last_threshold - state->threshold);
if (SPA_UNLIKELY(state->last_threshold != state->threshold)) {
int32_t diff = (int32_t) (state->last_threshold - state->threshold);
spa_log_trace(state->log, NAME" %p: follower:%d quantum change %d -> %d (%d)",
state, follower, state->last_threshold, state->threshold, diff);
if (diff < 0)
state->next_time += diff / corr * 1e9 / state->rate;
if (SPA_UNLIKELY(diff != 0)) {
err -= diff;
spa_log_trace(state->log, NAME" %p: follower:%d quantum change %d -> %d (%d) %f",
state, follower, state->last_threshold, state->threshold, diff, err);
state->last_threshold = state->threshold;
}
err = SPA_CLAMP(err, -state->max_error, state->max_error);
corr = spa_dll_update(&state->dll, err);
if (diff < 0)
state->next_time += diff / corr * 1e9 / state->rate;
if (SPA_UNLIKELY((state->next_time - state->base_time) > BW_PERIOD)) {
state->base_time = state->next_time;