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audio: hook refine position to alsa stream

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* Fixes audio syncronization during video playback.
* Account start_threshold as device specific latency for ALSA HDMI and
  tinyalsa [1] (3.5mm jack, DAC & USB) output.
* Remove unneeded pcm call to query buffer size.

[1]: https://android.googlesource.com/platform/external/tinyalsa_new/+/refs/tags/android-16.0.0_r1/include/tinyalsa/pcm.h#214
This commit is contained in:
Konsta
2025-10-29 18:19:18 +02:00
parent 688b88189e
commit dcad73115c
2 changed files with 10 additions and 6 deletions
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11
audio/alsa_utils/alsa_device_proxy.c
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@@ -385,7 +385,8 @@ int proxy_get_presentation_position(const alsa_device_proxy * proxy,
struct timespec alsaTs;
if (proxy->pcm != NULL
&& pcm_get_htimestamp(proxy->pcm, &avail, &alsaTs) == 0) {
const size_t kernel_buffer_size = pcm_get_buffer_size(proxy->pcm);
const size_t kernel_buffer_size = proxy->alsa_config.period_count
* proxy->alsa_config.period_size;
if (avail > kernel_buffer_size) {
// pcm_get_htimestamp() computes the available frames by comparing the ALSA driver
// hw_ptr and the appl_ptr levels. In underrun, the hw_ptr may keep running and report
@@ -402,6 +403,8 @@ int proxy_get_presentation_position(const alsa_device_proxy * proxy,
// It is possible to compensate for additional driver and device delay
// by changing signed_frames. Example:
// signed_frames -= 20 /* ms */ * proxy->alsa_config.rate / 1000;
signed_frames -= proxy->alsa_config.period_count
* proxy->alsa_config.period_size; // start_threshold
if (signed_frames >= 0) {
*frames = signed_frames;
ret = 0;
@@ -419,7 +422,8 @@ int hdmi_proxy_get_presentation_position(const alsa_device_proxy * proxy,
struct timespec alsaTs;
if (proxy->pcm_alsa != NULL
&& snd_pcm_htimestamp(proxy->pcm_alsa, &avail, &alsaTs) == 0) {
const snd_pcm_uframes_t kernel_buffer_size = proxy->alsa_config.period_count * proxy->alsa_config.period_size * 2;
const snd_pcm_uframes_t kernel_buffer_size = proxy->alsa_config.period_count
* proxy->alsa_config.period_size * 2;
if (avail > kernel_buffer_size) {
// pcm_get_htimestamp() computes the available frames by comparing the ALSA driver
// hw_ptr and the appl_ptr levels. In underrun, the hw_ptr may keep running and report
@@ -436,7 +440,8 @@ int hdmi_proxy_get_presentation_position(const alsa_device_proxy * proxy,
// It is possible to compensate for additional driver and device delay
// by changing signed_frames. Example:
// signed_frames -= 20 /* ms */ * proxy->alsa_config.rate / 1000;
signed_frames -= EXTRA_START_THRESHOLD;
signed_frames -= proxy->alsa_config.period_count
* proxy->alsa_config.period_size + EXTRA_START_THRESHOLD; // start_threshold
if (signed_frames >= 0) {
*frames = signed_frames;
ret = 0;