From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: Henrik Austad <henrik@austad.us>,
Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: alsa-devel@alsa-project.org, netdev@vger.kernel.org,
Richard Cochran <richardcochran@gmail.com>,
linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@linaro.org>,
linux-media@vger.kernel.org
Subject: Re: [alsa-devel] [very-RFC 0/8] TSN driver for the kernel
Date: Mon, 20 Jun 2016 13:08:27 +0200 [thread overview]
Message-ID: <9a5abd48-4da3-945d-53c9-b6d37010ab0d@linux.intel.com> (raw)
In-Reply-To: <20160618224549.GF32724@icarus.home.austad.us>
> Presentation time is either set by
> a) Local sound card performing capture (in which case it will be 'capture
> time')
> b) Local media application sending a stream accross the network
> (time when the sample should be played out remotely)
> c) Remote media application streaming data *to* host, in which case it will
> be local presentation time on local soundcard
>
>> This value is dominant to the number of events included in an IEC 61883-1
>> packet. If this TSN subsystem decides it, most of these items don't need
>> to be in ALSA.
>
> Not sure if I understand this correctly.
>
> TSN should have a reference to the timing-domain of each *local*
> sound-device (for local capture or playback) as well as the shared
> time-reference provided by gPTP.
>
> Unless an End-station acts as GrandMaster for the gPTP-domain, time set
> forth by gPTP is inmutable and cannot be adjusted. It follows that the
> sample-frequency of the local audio-devices must be adjusted, or the
> audio-streams to/from said devices must be resampled.
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.
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.
next prev parent reply other threads:[~2016-06-20 11:14 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 ` Pierre-Louis Bossart [this message]
2016-06-20 11:49 ` [alsa-devel] " 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
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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