[gst-devel] channel configuration

[Ronald S. Bultje]

On Wed, 2004-04-28 at 03:19, David Schleef wrote:
> On Tue, Apr 27, 2004 at 08:37:03PM +0200, Ronald S. Bultje wrote:
> > The second is to take the Matroska approach, where every channel has a
> > degree-number associated with it, which is the number of degrees (0-360)
> > from the center front speaker (point-of-origin). This is harder to
> > implement, especially because of the theoretical option that the
> > left-front-speaker in the audiosink is located slightly differently from
> > the intended left-front speaker position in the audio source. The buffer
> > has a similar layout as in the previous proposal, except that the order
> > of samples is as given in the array of channel positions instead of
> > simply left-to-right, front-to-rear-to-lfe.
> 
> I like this better.  The only issue I see is for channels that don't
> have a spatial location, such as a subwoofer channel.  What does
> matroska do about this?  Are there other non-angular issues
> 
> To address your issue, we could use this system, but have a policy
> that FL and FR sources are at -30 and +30.  (Eh, depending on the
> sign convention -- again, what does matroska use?)  Or, you could
> convince a local audio expert to write a converter from one spatial
> layout to another. :)

"All successive (audio) channels are specified by their horizontal angle
position. The position is coded using a signed int8 which represents the
fraction of 180°/x, the 0 reference is the center (front).

For example:

1 channel:	Center				0 (0)
2 channels:	Left + Right			-30° (-22), +30° (+22)
		Center + Surround		0(0), 180° (-128)
3 channels:	Left + Right + Center	???	-35° (-25), +35° (+25), 0 (0)
		Left + Center + Right	???	-35° (-25), 0, +35° (+25)
		Left + Right + Surround		-30° (-22), +30° (+22), 180° (-128)
4 channels:
5 channels:	Left + Right + Center + Left Surround + Right Surround	-35°
(-25), +35° (+25), 0,
-110° (-103), +110° (+103)"

(from: http://matroska.org/technical/specs/channelposition/index.html)

Apparently, there's no such thing as LFE... Can our Matroska people
enlighten us please?

Ronald