From: Daniel Mack <zonque@gmail.com>
To: Zhang wei <zhangwei@vimicro.com>
Cc: ALSA development <alsa-devel@alsa-project.org>,
broonie@opensource.wolfsonmicro.com, lgirdwood@gmail.com
Subject: Re: 答复: 答复: how to combine mutil-channel in playback or capture?
Date: Fri, 22 Mar 2013 11:19:06 +0100 [thread overview]
Message-ID: <514C301A.6050408@gmail.com> (raw)
In-Reply-To: <6B947C8AC4195040A8C6876A496C644A08195768@BJ-MAIL-04.vimicro.com>
Hi,
please don't top-post.
On 22.03.2013 11:11, Zhang wei wrote:
> But what is the mechanism to synchronize the data from different
> channel,and maybe different channel pairs use different DMA buffer.
You can try and see if syncing the individual, non-combinded PCM streams
helps:
http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html#pcm_sync
> So, I guess ,about the combine ,according to the alsa.conf,the alsa-lib
> opened the 4 devices(in my case) and got every channel paris’s data in
> turns in a monent. And then combine them together in order as one frame?
It will feed the input to all pcm streams. I don't really know if it
uses the sync mechanism on that, but I'd guess so.
> Because all the CODEC have the same clock timing,so the different DMA
> buffer stored the different channel data for the same moment. Alsa-lib
> obtains the same size data from each buffer in turns in once.repeat it
> again and again.
>
> Right?
Yes, and so the streams won't drift.
Why don't you just go ahead and try it? You should play back some wav
file with a test pattern which you can recognize on a DSO or IIS
analyzer on the bus. Then see if they are in sync.
Daniel
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prev parent reply other threads:[~2013-03-22 10:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-22 8:08 how to combine mutil-channel in playback or capture? Zhang wei
2013-03-22 8:20 ` Daniel Mack
[not found] ` <6B947C8AC4195040A8C6876A496C644A081956F9@BJ-MAIL-04.vimicro.com>
2013-03-22 9:27 ` 答复: " Daniel Mack
[not found] ` <6B947C8AC4195040A8C6876A496C644A08195768@BJ-MAIL-04.vimicro.com>
2013-03-22 10:19 ` Daniel Mack [this message]
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