* RFC: Add support for monotonic clock for 2.6 @ 2007-02-27 14:52 Jaroslav Kysela 2007-03-07 22:18 ` Takashi Iwai 0 siblings, 1 reply; 7+ messages in thread From: Jaroslav Kysela @ 2007-02-27 14:52 UTC (permalink / raw) To: ALSA development 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() Jaroslav ----- Jaroslav Kysela <perex@suse.cz> 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: RFC: Add support for monotonic clock for 2.6 2007-02-27 14:52 RFC: Add support for monotonic clock for 2.6 Jaroslav Kysela @ 2007-03-07 22:18 ` Takashi Iwai 2007-03-07 22:33 ` James Courtier-Dutton 0 siblings, 1 reply; 7+ messages in thread From: Takashi Iwai @ 2007-03-07 22:18 UTC (permalink / raw) To: Jaroslav Kysela; +Cc: ALSA development 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 ------------------------------------------------------------------------- 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: RFC: Add support for monotonic clock for 2.6 2007-03-07 22:18 ` Takashi Iwai @ 2007-03-07 22:33 ` James Courtier-Dutton 2007-03-07 22:48 ` Takashi Iwai 2007-03-08 6:57 ` Jaroslav Kysela 0 siblings, 2 replies; 7+ messages in thread From: James Courtier-Dutton @ 2007-03-07 22:33 UTC (permalink / raw) To: Takashi Iwai; +Cc: ALSA development, Jaroslav Kysela 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! James ------------------------------------------------------------------------- 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: RFC: Add support for monotonic clock for 2.6 2007-03-07 22:33 ` James Courtier-Dutton @ 2007-03-07 22:48 ` Takashi Iwai 2007-03-07 23:03 ` James Courtier-Dutton 2007-03-08 6:57 ` Jaroslav Kysela 1 sibling, 1 reply; 7+ messages in thread From: Takashi Iwai @ 2007-03-07 22:48 UTC (permalink / raw) To: James Courtier-Dutton; +Cc: ALSA development, Jaroslav Kysela 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 ------------------------------------------------------------------------- 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: RFC: Add support for monotonic clock for 2.6 2007-03-07 22:48 ` Takashi Iwai @ 2007-03-07 23:03 ` James Courtier-Dutton 2007-03-08 7:01 ` Jaroslav Kysela 0 siblings, 1 reply; 7+ messages in thread From: James Courtier-Dutton @ 2007-03-07 23:03 UTC (permalink / raw) To: Takashi Iwai; +Cc: ALSA development, Jaroslav Kysela 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. James ------------------------------------------------------------------------- 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: RFC: Add support for monotonic clock for 2.6 2007-03-07 23:03 ` James Courtier-Dutton @ 2007-03-08 7:01 ` Jaroslav Kysela 0 siblings, 0 replies; 7+ messages in thread From: Jaroslav Kysela @ 2007-03-08 7:01 UTC (permalink / raw) To: James Courtier-Dutton; +Cc: Takashi Iwai, ALSA development 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@suse.cz> 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: RFC: Add support for monotonic clock for 2.6 2007-03-07 22:33 ` James Courtier-Dutton 2007-03-07 22:48 ` Takashi Iwai @ 2007-03-08 6:57 ` Jaroslav Kysela 1 sibling, 0 replies; 7+ messages in thread From: Jaroslav Kysela @ 2007-03-08 6:57 UTC (permalink / raw) To: James Courtier-Dutton; +Cc: Takashi Iwai, ALSA development On Wed, 7 Mar 2007, 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! I'd like to use these timestamps to do jitter (sample rate) corrections among multiple soundcards. Unfortunately, because gettimeofday is not monotonic, the timestamps are not accurate enough. Also, direct plugins might use these timestamps to do more accurate stream start. Jaroslav ----- Jaroslav Kysela <perex@suse.cz> 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 ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2007-03-08 7:01 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2007-02-27 14:52 RFC: Add support for monotonic clock for 2.6 Jaroslav Kysela 2007-03-07 22:18 ` Takashi Iwai 2007-03-07 22:33 ` James Courtier-Dutton 2007-03-07 22:48 ` Takashi Iwai 2007-03-07 23:03 ` James Courtier-Dutton 2007-03-08 7:01 ` Jaroslav Kysela 2007-03-08 6:57 ` Jaroslav Kysela
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