All of lore.kernel.org
 help / color / mirror / Atom feed
From: Tim Cussins <timcussins@eml.cc>
To: Raymond Yau <superquad.vortex2@gmail.com>
Cc: nstoughton@aether.com, tiwai@suse.de,
	alsa-devel@alsa-project.org,
	pierre-louis.bossart@linux.intel.com
Subject: Re: [PATCH v2 3/3] snd_pcm_start_at: Implement snd_pcm_start_at for system and audio tstamp types.
Date: Fri, 19 Dec 2014 11:41:17 +0000	[thread overview]
Message-ID: <54940EDD.8010007@eml.cc> (raw)
In-Reply-To: <CAN8cciYLnTBreS=wf4Ax4o8r-zLJ9fYaTXeyQd-fosaXdn_nVA@mail.gmail.com>

On 17/12/14 23:37, Raymond Yau wrote:
>  >
>  > System tstamp types rely on high-res timers.
>  > Audio tstamp types delegate to the pcm driver.
>  > Current start_at timer is cancelled on attempt to change stream state.
>
> http://git.alsa-project.org/?p=alsa-lib.git;a=blob_plain;f=test/timer.c;hb=HEAD
>
> Are there any difference between sound card's timer with high res
> timer/wall clock time stamp ?
>
> It seem those sound cards timer have resolution and max tick
>
> https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/ymfpci?id=6e2efaacb3579fd9643d0dc59963b58b801c03a1
>
> snd_timer_status_get_resolution
>
> The clock tick counters are 32 bits and wrap around
>
> This may mean that snd_pcm_start_at can only start within certian time
> interval
>

[and this time I'll post to the list :)]

I had presumed it would be pretty simple to use the timer-wrap interrupt 
to maintain a monotonic sense of time. Hardware that can't support this 
might not be able to support start_at.

T

      reply	other threads:[~2014-12-19 11:41 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-17 17:29 [PATCH v2 1/3] snd_pcm_start_at: Add enum for timestamp class, and helper struct for start_at ioctl Tim Cussins
2014-12-17 17:29 ` [PATCH v2 2/3] snd_pcm_start_at: Add snd_pcm_ops so that driver can handle start_at requests Tim Cussins
2014-12-17 17:29 ` [PATCH v2 3/3] snd_pcm_start_at: Implement snd_pcm_start_at for system and audio tstamp types Tim Cussins
2014-12-17 23:37   ` Raymond Yau
2014-12-19 11:41     ` Tim Cussins [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=54940EDD.8010007@eml.cc \
    --to=timcussins@eml.cc \
    --cc=alsa-devel@alsa-project.org \
    --cc=nstoughton@aether.com \
    --cc=pierre-louis.bossart@linux.intel.com \
    --cc=superquad.vortex2@gmail.com \
    --cc=tiwai@suse.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.