On Wed, 7 Mar 2007, James Courtier-Dutton wrote: > Takashi Iwai wrote: > > At Wed, 07 Mar 2007 22:33:25 +0000, > > James Courtier-Dutton wrote: > > > Takashi Iwai wrote: > > > > At Tue, 27 Feb 2007 15:52:41 +0100 (CET), > > > > Jaroslav Kysela wrote: > > > > > Hi, > > > > > > > > > > in 2.6 kernels, we can use ktime_get_ts() function to > > > > > get monotonic time which can be used for PCM timestamps. I > > > > > would propose to reuse the SNDRV_PCM_IOCTL_TSTAMP ioctl to > > > > > enable using of monotonic clock. > > > > > The "enable" (int) argument might mean: > > > > > > > > > > 0: standard clock - getnstimeofday() > > > > > 1: standard clock - getnstimeofday() - for "compatibility" > > > > > 2: monotonic clock - ktime_get_ts() > > > > Good to add a new feature... but is there any user of this PCM > > > > timestamp so far? I see some good purposes but rarely seen in > > > > the > > > > reality, unfortunately... > > > > > > > > > > > > Takashi > > > > > > > There are some good applications for it, but I have not got round to > > > writing them yet! > > > > Me too ;) But, I remember some difficulties regarding the > > timestamping at the last time I tried (quite ago). The timestamp is > > somewhat hard to use because it's updated at each pointer or status > > update although I wanted to get the exact time only at the period > > boundary. Maybe these usability issues should be sorted out all > > together. > > > > > > Takashi > > Yes, timestamp at period boundary would be more useful. I had not looked at > the current timestamp in enough details. A timestamp generated in the IRQ > routine would probably be the best. Could the timestamp be attached to a > particular PCM sample in the buffer. I.e. The app would retrieve the > timestamp, and be told that that timestamp applies to the sample X samples > from now, if using the snd_pcm_read() function. If SNDRV_PCM_TSTAMP_MMAP is set (snd_pcm_sw_params_set_tstamp_mode(SND_PCM_TSTAMP_MMAP)) , the timestamp is updated at each change of hw_ptr in driver (thus also in the interrupt handler). Jaroslav ----- Jaroslav Kysela <perex@xxxxxxx> Linux Kernel Sound Maintainer ALSA Project, SUSE Labs ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
