Re: [codec] possible issues to track

[Michael Knappe <[e-mail]>]

Thanks Peter! Some notes inline...



On 3/25/10 2:12 PM, "Peter Saint-Andre" <[e-mail]> wrote:

> During the WG session, I kept notes about some issues that we might want
> to track (on list or in the tracker -- I'll leave it up to the
> continuing chairs to decide how). They are:
> 
> - delay is not *constant* on the Internet
> - add reference to ITU G.107 regarding echo
[MEK] we need to consider delay impairment factors due to both echo and
absolute latency
> - better explain echo and algorithmic delay < 10ms
[MEK] need to understand at what point a reduction in algorithmic delay
along with achievable network latencies can significantly improve perception
of echo (e.g. Reducing noticeability of acoustic echo, and/or pulling
round-trip delays in to the point that an echo moves from being perceptively
discrete to an integrated sidetone signal)
> - avoid phrasing subjective comparision in relation to ITU codecs
> - clarify whether each requirement is nice or necessary
> - clarify the measurability of each requirement
> - clarify requirement about bit-exactness
[MEK] we will need to specify whether our final reference code is fully bit
exact, or whether some or all elements can be bit compatible. We should also
specify whether any portions of said algorithms could be 'upgradeable' (e.g.
Having a stock PLC algorithm that could be replaced with a better PLC in the
future)

> - mention DTMF in requirements
[MEK] some simple talk-off tests should be done to determine if in-band DTMF
(and potentially other call progress tones) are carried in-band without
sufficient degradation as to cause a DTMF detector misread.

> - mention synchronization of audio with other media
[MEK] further investigation is needed to determine if there are any possible
implications or dependencies for a codec's use in video applications

> 
> If I missed anything, post to the list.

- multi-channel carriage: not sure if we mentioned this during the WG
session, but we need to decide if we will support any kind of joint channel
coding (current consensus so far is to keep all channels separable). We also
should also reference multi-channel packing within RTP (RFC 3551 sec 4.1).


> 
> Peter