From 124aa40f64c3e61642e4f067905cad5877e71d11 Mon Sep 17 00:00:00 2001 From: Wim Taymans Date: Tue, 2 Sep 2025 14:13:19 +0200 Subject: [PATCH] alsa: use 2 (or 3 for batch) periods in IRQ mode Some drivers (Firewire) have a latency depending on the ALSA buffer size instead of the period size. In IRQ mode, we can safely use 2 (or 3 for batch devices) periods because we always need to reconfigure the hardware when we want to change the period and so we don't need to keep some headroom like we do for timer based scheduling. See #4785 --- spa/plugins/alsa/alsa-pcm.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/spa/plugins/alsa/alsa-pcm.c b/spa/plugins/alsa/alsa-pcm.c index 5fece06ce..48af0e3f8 100644 --- a/spa/plugins/alsa/alsa-pcm.c +++ b/spa/plugins/alsa/alsa-pcm.c @@ -2335,8 +2335,13 @@ int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_ state->period_frames = period_size; - if (state->default_period_num != 0) { - periods = state->default_period_num; + if (state->default_period_num != 0 || state->disable_tsched) { + if (state->default_period_num != 0) + /* period number given use that */ + periods = state->default_period_num; + else + /* IRQ mode, use 2 periods or 3 for batch */ + periods = state->is_batch ? 3 : 2; CHECK(snd_pcm_hw_params_set_periods_near(hndl, params, &periods, &dir), "set_periods"); state->buffer_frames = period_size * periods; } else {