Commit d3d39890 authored by Rémi Denis-Courmont's avatar Rémi Denis-Courmont

aout_TimeReport: feedback timing from audio output to audio decoder

Currently, this is used to trigger resampling in the audio "input"
(i.e. filters) as before.
parent 94b75f19
......@@ -244,6 +244,8 @@ VLC_API void aout_VolumeSoftInit( audio_output_t * );
VLC_API void aout_VolumeHardInit( audio_output_t *, aout_volume_cb );
VLC_API void aout_VolumeHardSet( audio_output_t *, float, bool );
VLC_API void aout_TimeReport(audio_output_t *, mtime_t);
VLC_API int aout_ChannelsRestart( vlc_object_t *, const char *, vlc_value_t, vlc_value_t, void * );
/* */
......
......@@ -311,3 +311,46 @@ bool aout_DecIsEmpty (audio_output_t *aout)
aout_unlock (aout);
return end_date == VLC_TS_INVALID || end_date <= mdate();
}
/**
* Notifies the audio input of the drift from the requested audio
* playback timestamp (@ref block_t.i_pts) to the anticipated playback time
* as reported by the audio output hardware.
* Depending on the drift amplitude, the input core may ignore the drift
* trigger upsampling or downsampling, or even discard samples.
* Future VLC versions may instead adjust the input decoding speed.
*
* The audio output plugin is responsible for estimating the ideal current
* playback time defined as follows:
* ideal time = buffer timestamp - (output latency + pending buffer duration)
*
* Practically, this is the PTS (block_t.i_pts) of the current buffer minus
* the latency reported by the output programming interface.
* Computing the estimated drift directly would probably be more intuitive.
* However the use of an absolute time value does not introduce extra
* measurement errors due to the CPU scheduling jitter and clock resolution.
* Furthermore, the ideal while it is an abstract value, is easy for most
* audio output plugins to compute.
* The following definition is equivalent but depends on the clock time:
* ideal time = real time + drift
* @note If aout_LatencyReport() is never called, the core will assume that
* there is no drift.
*
* @param ideal estimated ideal time as defined above.
*/
void aout_TimeReport (audio_output_t *aout, mtime_t ideal)
{
mtime_t delta = mdate() - ideal /* = -drift */;
aout_assert_locked (aout);
if (delta < -AOUT_MAX_PTS_ADVANCE || +AOUT_MAX_PTS_DELAY < delta)
{
aout_owner_t *owner = aout_owner (aout);
msg_Warn (aout, "not synchronized (%"PRId64" us), resampling",
delta);
if (date_Get (&owner->sync.date) != VLC_TS_INVALID)
date_Move (&owner->sync.date, delta);
}
}
......@@ -29,6 +29,7 @@ aout_VolumeUp
aout_ToggleMute
aout_IsMuted
aout_SetMute
aout_TimeReport
aout_VolumeNoneInit
aout_VolumeSoftInit
aout_VolumeHardInit
......
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