Re: Minutes of audio WG teleconference, 2012-04-25

Hi James, all

On 26 Apr 2012, at 11:26, Wei, James wrote:

> For issue-9(multiple channel), should we explicitly point out how many kinds of layout is mandatory? 
> 
> such as mono/stereo/5.1 and corresponding up/down mixing are MUST HAVE . And the support for quad/7.1 etc can be next level ones?  

Should we explicitly specify the layouts? I don't know how stable they are – I guess the 5 you mentioned aren't going away, but is the industry likely to come up with another in the years where this spec will be stable?

I was thinking our needs for multi-channels can be described with the following requirements:

* The ability to match the number of channels supported by the hardware (with no upper limit?)
* The ability to up mix any source to match the number of channels of the system
* The ability to use as source an audio stream with more channels than the system supports
* The ability to down mix a source or stream to any number of channels, down to mono

These 4 requirements would probably cover all scenarios. I think the way they are phrased does raise two questions:

1) What happens if a stream is being down mixed to a number of channels strictly inferior to the number of channels in the system. Should it be considered to still have the same number of channels, but have all but n be mute?

2) What happens when a source with many channels (say a 5.1 AC3 file) is piped into a system with only 2 channel support. Should our API keep it as 5.1? or down-mix it? And if so, how? automatically?


Olivier