[alsa-devel] snd_pcm_htimestamp & more PCM mmap timestamping in driver

Takashi Iwai tiwai at suse.de
Wed Jan 9 16:00:38 CET 2008

At Wed, 9 Jan 2008 14:17:28 +0100 (CET),
Jaroslav Kysela wrote:
> Hi all,
> 	I just added snd_pcm_htimestamp() function to alsa-lib:
> int snd_pcm_htimestamp(snd_pcm_t *pcm, snd_pcm_uframes_t *avail, 
> 		       snd_htimestamp_t *tstamp);

Thanks, looks good.
I suppose the unimplemented stuff shall be implemented soon in near

> 	If you have any complaints, please, do now.
> 	Also, I would like to change SNDRV_PCM_TSTAMP_MMAP semantics to 
> SNDRV_PCM_TSTAMP_ENABLE - when hw_ptr is updated in the driver, a 
> timestamp would be always grabbed to ensure that we have always a valid 
> timestamp & position pair. In current implementation, if an application 
> updates hw_ptr in driver (using for example PCM delay ioctl), timestamp 
> grabbed in the interrupt handler won't be associated with any real ring 
> buffer position which makes things complicated and not too much abstract. 
> Opinions?

Sounds reasonable to me.


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