Re: [Intel-gfx] [RFC][PATCH] ELD routines and proc interface

From: Wu Fengguang <wfg@linux.intel.com>
To: Shane W <shane-intel@csy.ca>
Cc: alsa-devel <alsa-devel@alsa-project.org>,
	"Ma, Ling" <ling.ma@intel.com>,
	intel-gfx@lists.freedesktop.org, Takashi Iwai <tiwai@suse.de>,
	xorg@lists.freedesktop.org, "Fu, Michael" <michael.fu@intel.com>
Subject: Re: [Intel-gfx] [RFC][PATCH] ELD routines and proc interface
Date: Fri, 21 Nov 2008 09:59:10 +0800	[thread overview]
Message-ID: <20081121015910.GB10734@localhost> (raw)
In-Reply-To: <20081121014649.GA12072@csy.ca>

On Thu, Nov 20, 2008 at 05:46:49PM -0800, Shane W wrote:
> On Fri, Nov 21, 2008 at 09:36:55AM +0800, Wu Fengguang wrote:
> > 
> > > supports coding type AC-3: channels = 6, rates = 44100
> > > 48000 88200, max bitrate = 640000
> > > supports coding type DTS: channels = 7, rates = 44100 48000
> > > 88200 176400 192000, max bitrate = 1536000
> > > supports coding type DSD (One Bit Audio): channels = 6,
> > > rates = 48000
> > 
> > It's weird that DTS supports 7 channels while DSD supports 6.
> > DTS is simple the compressed form of DSD.
> 
> Hmm, I thought DTS was just another way of compressing PCM
> whereas DSD is the format used on SACD disks, IE 6 channel.
> http://en.wikipedia.org/wiki/Direct_Stream_Digital

Well my source is a bit different ;-)

http://en.wikipedia.org/wiki/Super_Audio_CD

DST

To reduce the space and bandwidth requirements of DSD (2.8 Mbit/s per
channel), a lossless data compression method called Direct Stream
Transfer (DST) is used — DST compression is compulsory for
multi-channel regions and optional for stereo regions. This typically
compresses by a factor of between two and three, allowing a disc to
contain 80 minutes of both 2-channel and 5.1-channel sound.

> > > The speakers 0 line is a bit confusing, not sure if that's
> > 
> > Yes it's unexpected. Do you know its real speaker numbers and
> > allocations? Does it provide some number of line-out ports?
> 
> There are six speakers connected, fl, ct, fr, rl, rr and
> lfe.

Takashi, I'd suggest to support writing to the ELD proc interface to
alter the internal ELD struct. This could let users debug/fix quicks
conveniently. But sure these fixes should eventually be incorporated
into the kernel so that it just works.

> > > what's doing it.  I am using:
> > > aplay 51test.wav
> > > 
> > > which I have put here:
> > > http://www.csy.ca/~shane/51test.wav
> > 
> > I hear only "front left" and "front right" in my T61 :-)
> 
> Yeah, you should get:
> Front left
> Center
> Rear left
> Rear right
> and a little boom from the sub
> 
> If you encode 51test.wav to ac3 and stream through hdmi
> directly, it does this properly.

OK, so 5.1 AC3 audio plays properly on HDMI?

Thanks,
Fengguang
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