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alsa: fix capture timings and drift

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Don't reschedule a timeout when we have less samples available than the
target but only reschedule when we have less that the required amount we
need to read. This ensures that we hover around the target level and the
timeouts/rate matching adapts correctly. Previously we would only rate
match if the have at least the target amount of samples, which would
then always result in a possitive rate adjustment and cause drift.

For capture, make sure that there is at least 32 samples of headroom
when we are not using IRQ mode to handle jitter in the timer wakeup.

For capture of batch devices this results in (for a 1024 quantum) a
target buffer fill level of 1024 + 512, and we will read if there are at
least 1024 samples available.

For non-batch devices we aim for a target buffer fill level of 1024 + 32
and read if there are at least 1024 samples available.
This commit is contained in:
Wim Taymans 2023-04-10 15:02:29 +02:00
parent 4b6e0df411
commit d59e1094cd
1 changed files with 18 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

30
spa/plugins/alsa/alsa-pcm.c
View file

@ -1616,10 +1616,17 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
}
state->headroom = state->default_headroom;
/* If tsched is disabled, we know the pointers are updated when we wake
* up, so we don't need the additional headroom */
if (is_batch && !state->disable_tsched)
state->headroom += period_size;
if (!state->disable_tsched) {
/* If tsched is disabled, we know the pointers are updated when we wake
* up, so we don't need the additional headroom */
if (is_batch)
state->headroom += period_size;
/* add 32 extra samples of headroom to handle jitter in capture */
if (state->stream == SND_PCM_STREAM_CAPTURE)
state->headroom = SPA_MAX(state->headroom, 32u);
}
state->max_delay = state->buffer_frames / 2;
if (spa_strstartswith(state->props.device, "a52") ||
@ -1921,9 +1928,7 @@ static int get_status(struct state *state, uint64_t current_time,
*delay = state->buffer_frames - avail;
} else {
*delay = avail;
*target = SPA_MAX(*target, state->read_size);
if (state->matching)
*target += 32;
*target = SPA_MAX(*target, state->read_size + state->headroom);
}
*target = SPA_CLAMP(*target, state->min_delay, state->max_delay);
return 0;
@ -2007,8 +2012,8 @@ static int update_time(struct state *state, uint64_t current_time, snd_pcm_sfram
state->clock->next_nsec = state->next_time;
}
spa_log_trace_fp(state->log, "%p: follower:%d %"PRIu64" %f %ld %f %f %u",
state, follower, current_time, corr, delay, err, state->threshold * corr,
spa_log_trace_fp(state->log, "%p: follower:%d %"PRIu64" %f %ld %ld %f %f %u",
state, follower, current_time, corr, delay, target, err, state->threshold * corr,
state->threshold);
return 0;
@ -2483,14 +2488,15 @@ static int handle_capture(struct state *state, uint64_t current_time,
int res;
struct spa_io_buffers *io;
if (SPA_UNLIKELY(delay < target)) {
spa_log_trace(state->log, "%p: early wakeup %ld %ld", state, delay, target);
if (SPA_UNLIKELY(delay < state->read_size)) {
spa_log_trace(state->log, "%p: early wakeup %ld %ld %d", state, delay, target,
state->read_size);
state->next_time = current_time + (target - delay) * SPA_NSEC_PER_SEC /
state->rate;
return -EAGAIN;
}
if (SPA_UNLIKELY(res = update_time(state, current_time, delay, target, false)) < 0)
if (SPA_UNLIKELY((res = update_time(state, current_time, delay, target, false)) < 0))
return res;
if ((res = spa_alsa_read(state)) < 0)