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alsa: improve force_rate handling

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Replace force_rate with force_quantum. We use force_rate when we need
to play an IEC958 or a DSD format but it does not make sense to just
force the rate without also forcing the duration.

This is also what happens when doing IRQ based scheduling, we then force
both the duration and rate of the graph so we can reuse this logic.

Also when forcing a quantum, take into account the suggested duration
and rate of the graph and scale that with the currently configured rate
for the period size. This gives a quantum that will match the requested
rate better. This is important for the DSD, where rate are very high and
we want the period size to be something reasonable relative to the
selected graph rate.

For batch devices (and when using a timer) we also configure a period
size that is half the duration of the quantum, to make sure we get some
headroom. We however need to force the full duration as the quantum, so
keep track of this scaling and apply when calculating the duration.
This commit is contained in:
Wim Taymans 2025-09-25 12:29:05 +02:00
parent 65e49b38d1
commit f8389cbdb7
2 changed files with 25 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

40
spa/plugins/alsa/alsa-pcm.c
View file

@ -2069,7 +2069,7 @@ static void recalc_headroom(struct state *state)
int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_t flags)
{
unsigned int rrate, rchannels, val, rscale = 1;
unsigned int rrate, rchannels, val, rscale = 1, period_scale = 1;
snd_pcm_uframes_t period_size;
int err, dir;
snd_pcm_hw_params_t *params;
@ -2085,7 +2085,7 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
state->have_format, state->started);
state->use_mmap = !state->disable_mmap;
state->force_rate = false;
state->force_quantum = state->disable_tsched;
switch (fmt->media_subtype) {
case SPA_MEDIA_SUBTYPE_raw:
@ -2148,7 +2148,7 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
IEC958_AES0_CON_EMPHASIS_NONE | IEC958_AES0_NONAUDIO,
IEC958_AES1_CON_ORIGINAL | IEC958_AES1_CON_PCM_CODER,
0, aes3);
state->force_rate = true;
state->force_quantum = true;
break;
}
case SPA_MEDIA_SUBTYPE_dsd:
@ -2186,6 +2186,7 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
default:
return -ENOTSUP;
}
state->force_quantum = true;
break;
}
default:
@ -2316,10 +2317,13 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
default_period = SPA_SCALE32_UP(DEFAULT_PERIOD, state->rate, DEFAULT_RATE);
default_period = flp2(2 * default_period - 1);
/* no period size specified. If we are batch or not using timers,
* use the graph duration as the period */
if (period_size == 0 && (state->is_batch || state->disable_tsched))
period_size = state->position ? state->position->clock.target_duration : default_period;
/* no period size specified. If we are batch or forcing our quantum,
* use the graph requested quantum scaled by our rate */
if (period_size == 0 && (state->is_batch || state->force_quantum) && state->position) {
period_size = SPA_SCALE32_UP(state->position->clock.target_duration,
state->rate, state->position->clock.target_rate.denom);
period_size = flp2(period_size);
}
if (period_size == 0)
period_size = default_period;
@ -2330,6 +2334,7 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
* period size to our default so that we don't create too much
* headroom. */
period_size = SPA_MIN(period_size, default_period) / 2;
period_scale = 2;
} else {
/* disable ALSA wakeups */
if (snd_pcm_hw_params_can_disable_period_wakeup(params))
@ -2362,7 +2367,8 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
err = snd_pcm_hw_params_set_periods_min(hndl, params, &periods_min, &dir);
if (!err) {
CHECK(snd_pcm_hw_params_get_period_size_max(params, &period_size_max, &dir), "get_period_size_max");
CHECK(snd_pcm_hw_params_get_period_size_max(params, &period_size_max, &dir),
"get_period_size_max");
if (period_size > period_size_max)
period_size = SPA_MIN(period_size, flp2(period_size_max));
} else {
@ -2378,6 +2384,7 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_
}
state->period_frames = period_size;
state->duration = period_size * period_scale;
if (periods != UINT_MAX) {
CHECK(snd_pcm_hw_params_set_periods_near(hndl, params, &periods, &dir), "set_periods");
@ -2991,23 +2998,22 @@ static inline int check_position_config(struct state *state, bool starting)
uint64_t target_duration;
struct spa_fraction target_rate;
struct spa_io_position *pos;
bool can_force;
if (SPA_UNLIKELY((pos = state->position) == NULL))
return 0;
if (state->disable_tsched && (starting || state->started) && !state->following) {
target_duration = state->period_frames;
/* we can force rate/duration when we are the driver and started/starting */
can_force = (starting || state->started) && !state->following;
if (state->force_quantum && can_force) {
target_rate = SPA_FRACTION(1, state->rate);
pos->clock.target_duration = target_duration;
target_duration = state->duration;
pos->clock.target_rate = target_rate;
pos->clock.target_duration = target_duration;
} else {
target_rate = pos->clock.target_rate;
target_duration = pos->clock.target_duration;
if (state->force_rate && !state->following) {
target_rate = SPA_FRACTION(1, state->rate);
pos->clock.target_rate = target_rate;
} else {
target_rate = pos->clock.target_rate;
}
}
if (target_duration == 0 || target_rate.denom == 0)
return -EIO;

3
spa/plugins/alsa/alsa-pcm.h
View file

@ -169,6 +169,7 @@ struct state {
uint32_t delay;
uint32_t read_size;
uint32_t max_read;
uint32_t duration;
uint64_t port_info_all;
struct spa_port_info port_info;
@ -232,7 +233,7 @@ struct state {
unsigned int dsd_lsb:1;
unsigned int linked:1;
unsigned int is_batch:1;
unsigned int force_rate:1;
unsigned int force_quantum:1;
uint64_t iec958_codecs;