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rtp: include stream delay to a read position

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When a stream has some delay, a time t1 + delay has to be read in time
t1 to play it when expected.
Decrease target_buffer by delay to start playback sooner, so sound
is played at correct time when delay is applied.

Signed-off-by: Martin Geier <martin.geier@streamunlimited.com>
This commit is contained in:
Martin Geier 2025-05-21 12:14:58 +02:00 • committed by Wim Taymans
parent 1ed8f771bd
commit f8b0d0a43c
1 changed files with 24 additions and 2 deletions
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26
src/modules/module-rtp/audio.c
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@ -7,7 +7,9 @@ static void rtp_audio_process_playback(void *data)
struct impl *impl = data;
struct pw_buffer *buf;
struct spa_data *d;
struct pw_time pwt;
uint32_t wanted, timestamp, target_buffer, stride, maxsize;
uint32_t device_delay;
int32_t avail, flags = 0;
if ((buf = pw_stream_dequeue_buffer(impl->stream)) == NULL) {
@ -21,16 +23,36 @@ static void rtp_audio_process_playback(void *data)
maxsize = d[0].maxsize / stride;
wanted = buf->requested ? SPA_MIN(buf->requested, maxsize) : maxsize;
pw_stream_get_time_n(impl->stream, &pwt, sizeof(pwt));
/* Negative delay is used rarely, mostly for the combine stream.
* There, the delay is used as an offset value between streams.
* Here, negative delay values make no sense. It is safe to clamp
* delay values to 0 (see docs), so do that here. */
device_delay = SPA_MAX(pwt.delay, 0LL);
if (impl->io_position && impl->direct_timestamp) {
/* in direct mode, read directly from the timestamp index,
* because sender and receiver are in sync, this would keep
* target_buffer of samples available. */
/* Shift clock position by stream delay to compensate
* for processing and output delay. */
spa_ringbuffer_read_update(&impl->ring,
impl->io_position->clock.position);
impl->io_position->clock.position + device_delay);
}
avail = spa_ringbuffer_get_read_index(&impl->ring, &timestamp);
target_buffer = impl->target_buffer;
/* Reduce target buffer by the delay amount to start playback sooner.
* This compensates for the delay to the device. */
if (SPA_UNLIKELY(impl->target_buffer < device_delay)) {
pw_log_error("Delay to device (%" PRIu32 ") is higher than "
"the target buffer size (%" PRIu32 ")", device_delay,
impl->target_buffer);
target_buffer = 0;
} else {
target_buffer = impl->target_buffer - device_delay;
}
if (avail < (int32_t)wanted) {
enum spa_log_level level;