On Sun, 11 Nov 2018 19:21:29 +0100, Mike Brady wrote:
/* hardware definition */ static const struct snd_pcm_hardware snd_bcm2835_playback_hw = { .info = (SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER | SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID |
SNDRV_PCM_INFO_DRAIN_TRIGGER | SNDRV_PCM_INFO_SYNC_APPLPTR),
SNDRV_PCM_INFO_BATCH | SNDRV_PCM_INFO_DRAIN_TRIGGER |SNDRV_PCM_INFO_SYNC_APPLPTR),
As already mentioned, the addition of SNDRV_PCM_INFO_BATCH should be irrelevant with this change. Please create another patch to add this and clarify it in the changelog.
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 4e6110d778bd..574df7d7a1fa 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -229,19 +229,38 @@ static void update_audio_tstamp(struct snd_pcm_substream *substream, (runtime->audio_tstamp_report.actual_type == SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)) {
/** provide audio timestamp derived from pointer position* add delay only if requested*/
// provide audio timestamp derived from pointer positionaudio_frames = runtime->hw_ptr_wrap + runtime->status->hw_ptr;
if (runtime->audio_tstamp_config.report_delay) {
/** If the runtime->delay is greater than zero, it's a* genuine delay, e.g. a delay due to a hardware fifo.** But if the runtime->delay is less than zero, it's an* interpolated estimate of the number of frames output* since the hardware pointer was last updated.** It would be calculated in the pointer callback.* For example, for the bcm_2835 driver, it is calculated in* snd_bcm2835_pcm_pointer().*/if (runtime->delay < 0) {// The delay is an interpolated estimate... if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
audio_frames -= runtime->delay;elseaudio_frames += runtime->delay;
audio_frames += runtime->delay;} else {// The delay is a real delay. Add it if requested.if (runtime->audio_tstamp_config.report_delay) {if (substream->stream ==SNDRV_PCM_STREAM_PLAYBACK)audio_frames -= runtime->delay;elseaudio_frames += runtime->delay;}
Well, honestly speaking, I'm really not fond of changing the PCM core just for this.
Can we make bcm audio driver providing the finer pointer update instead? If we have a module option to disable that behavior, it's an enough excuse in case anyone really cares about the accuracy.
thanks,
Takashi