On 11.05.2018 10:09, Tanu Kaskinen wrote: > On Fri, 2018-05-04 at 21:10 +0200, Georg Chini wrote: >> The current code does not call snd_pcm_status_set_audio_htstamp_config() >> to configure the way timestamps are updated in ALSA. In kernel 4.14 and >> above a bug in ALSA has been fixed which changes timmestamp behavior. >> This leads to inconsistencies in the delay reporting because the time >> stamp no longer reflects the time when the delay was updated if the >> ALSA report_delay flag is not set. Therefore latencies are not calculated >> correctly. >> >> This patch uses snd_pcm_status_set_audio_htstamp_config() to set the >> ALSA report_delay flag to 1 before the call to snd_pcm_status(). With >> this, time stamps are updated as expected. >> --- >> >> Changes in v2: >> - updated commit message >> >> src/modules/alsa/alsa-util.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c >> index 61fb4903..b91a0e98 100644 >> --- a/src/modules/alsa/alsa-util.c >> +++ b/src/modules/alsa/alsa-util.c >> @@ -1187,6 +1187,7 @@ int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_status_t *status, snd_pcm_sframes >> size_t abs_k; >> int err; >> snd_pcm_sframes_t avail = 0; >> + snd_pcm_audio_tstamp_config_t tstamp_config; >> >> pa_assert(pcm); >> pa_assert(delay); >> @@ -1200,6 +1201,12 @@ int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_status_t *status, snd_pcm_sframes >> * avail, delay and timestamp values in a single kernel call to improve >> * timer-based scheduling */ >> >> + /* The time stamp configuration needs to be set so that the >> + * ALSA code will use the internal delay reported by the driver */ >> + tstamp_config.type_requested = 1; /* ALSA default time stamp type */ >> + tstamp_config.report_delay = 1; >> + snd_pcm_status_set_audio_htstamp_config(status, &tstamp_config); >> + >> if ((err = snd_pcm_status(pcm, status)) < 0) >> return err; >> > Looks good to me. > This patch breaks the build on older ALSA versions. Should we change the dependency to 1.1.0 which introduces snd_pcm_status_set_audio_htstamp_config() or make the usage of the function dependent on ALSA version?
