From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: alsa-devel@alsa-project.org, netdev@vger.kernel.org,
Henrik Austad <henrik@austad.us>,
linux-kernel@vger.kernel.org,
Takashi Sakamoto <o-takashi@sakamocchi.jp>,
Arnd Bergmann <arnd@linaro.org>,
linux-media@vger.kernel.org
Subject: Re: [alsa-devel] [very-RFC 0/8] TSN driver for the kernel
Date: Tue, 21 Jun 2016 10:45:18 -0700 [thread overview]
Message-ID: <07283da9-f6d1-c3b1-7989-a6fce7ca0ee6@linux.intel.com> (raw)
In-Reply-To: <20160620121838.GA5257@localhost.localdomain>
On 6/20/16 5:18 AM, Richard Cochran wrote:
> On Mon, Jun 20, 2016 at 01:08:27PM +0200, Pierre-Louis Bossart wrote:
>> The ALSA API provides support for 'audio' timestamps (playback/capture rate
>> defined by audio subsystem) and 'system' timestamps (typically linked to
>> TSC/ART) with one option to take synchronized timestamps should the hardware
>> support them.
>
> Thanks for the info. I just skimmed Documentation/sound/alsa/timestamping.txt.
>
> That is fairly new, only since v4.1. Are then any apps in the wild
> that I can look at? AFAICT, OpenAVB, gstreamer, etc, don't use the
> new API.
The ALSA API supports a generic .get_time_info callback, its
implementation is for now limited to a regular 'DMA' or 'link' timestamp
for HDaudio - the difference being which counters are used and how close
they are to the link serializer. The synchronized part is still WIP but
should come 'soon'
>
>> The intent was that the 'audio' timestamps are translated to a shared time
>> reference managed in userspace by gPTP, which in turn would define if
>> (adaptive) audio sample rate conversion is needed. There is no support at
>> the moment for a 'play_at' function in ALSA, only means to control a
>> feedback loop.
>
> Documentation/sound/alsa/timestamping.txt says:
>
> If supported in hardware, the absolute link time could also be used
> to define a precise start time (patches WIP)
>
> Two questions:
>
> 1. Where are the patches? (If some are coming, I would appreciate
> being on CC!)
>
> 2. Can you mention specific HW that would support this?
You can experiment with the 'dma' and 'link' timestamps today on any
HDaudio-based device. Like I said the synchronized part has not been
upstreamed yet (delays + dependency on ART-to-TSC conversions that made
it in the kernel recently)
next prev parent reply other threads:[~2016-06-21 17:49 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-11 23:01 [very-RFC 0/8] TSN driver for the kernel Henrik Austad
2016-06-11 23:01 ` [very-RFC 1/8] TSN: add documentation Henrik Austad
2016-06-11 23:01 ` [very-RFC 2/8] TSN: Add the standard formerly known as AVB to the kernel Henrik Austad
2016-06-11 23:01 ` [very-RFC 3/8] Adding TSN-driver to Intel I210 controller Henrik Austad
2016-06-11 23:01 ` [very-RFC 4/8] Add TSN header for the driver Henrik Austad
2016-06-11 23:01 ` [very-RFC 5/8] Add TSN machinery to drive the traffic from a shim over the network Henrik Austad
2016-06-11 23:01 ` [very-RFC 6/8] Add TSN event-tracing Henrik Austad
2016-06-12 16:58 ` Steven Rostedt
2016-06-12 21:25 ` Henrik Austad
2016-06-13 2:22 ` Steven Rostedt
2016-06-13 7:20 ` Henrik Austad
2016-06-11 23:01 ` [very-RFC 7/8] AVB ALSA - Add ALSA shim for TSN Henrik Austad
2016-06-15 11:49 ` Richard Cochran
2016-06-15 12:13 ` Henrik Austad
2016-06-15 12:43 ` Richard Cochran
2016-06-11 23:01 ` [very-RFC 8/8] MAINTAINERS: add TSN/AVB-entries Henrik Austad
2016-06-13 11:47 ` [very-RFC 0/8] TSN driver for the kernel Richard Cochran
2016-06-13 13:00 ` Henrik Austad
2016-06-13 19:32 ` Richard Cochran
2016-06-14 9:30 ` Henrik Austad
2016-06-14 18:26 ` Richard Cochran
2016-06-14 20:38 ` Henrik Austad
2016-06-15 7:04 ` Richard Cochran
2016-06-15 7:50 ` Henrik Austad
2016-06-15 11:41 ` Richard Cochran
2016-06-15 7:11 ` Richard Cochran
2016-06-13 19:37 ` Richard Cochran
2016-06-13 13:12 ` Arnd Bergmann
2016-06-13 15:56 ` John Fastabend
2016-06-14 8:35 ` Henrik Austad
2016-06-13 19:51 ` Richard Cochran
2016-06-14 11:18 ` One Thousand Gnomes
2016-06-14 17:04 ` Richard Cochran
2016-06-15 3:15 ` Takashi Sakamoto
2016-06-15 8:06 ` Richard Cochran
2016-06-18 5:22 ` Takashi Sakamoto
2016-06-18 22:45 ` Henrik Austad
2016-06-19 9:46 ` Richard Cochran
2016-06-20 8:05 ` Henrik Austad
2016-06-20 11:08 ` [alsa-devel] " Pierre-Louis Bossart
2016-06-20 11:49 ` Henrik Austad
2016-06-20 12:18 ` Richard Cochran
2016-06-20 12:31 ` Richard Cochran
2016-06-20 15:21 ` Richard Cochran
2016-06-21 5:54 ` Takashi Iwai
2016-06-21 6:38 ` Richard Cochran
2016-06-21 6:45 ` Takashi Iwai
2016-06-21 17:18 ` Pierre-Louis Bossart
2016-06-21 17:45 ` Pierre-Louis Bossart [this message]
2016-06-21 19:40 ` Richard Cochran
2016-06-22 12:36 ` Pierre-Louis Bossart
2016-06-23 10:38 ` Henrik Austad
2016-06-23 13:28 ` Richard Cochran
2016-06-15 3:27 ` Takashi Sakamoto
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