Subject: [avtext] New versions for the audio level drafts

From: Emil Ivov <[email-masked]>
Date: Mon, 14 Mar 2011 22:30:35 +0100

Hey folks,

We have just posted new versions of the audio level drafts and wanted to
discuss some of the changes before the meeting.

The most significant change consists in the addition of sample code that
shows how audio levels can be measured and rendered. The code was added
to the mixer-to-client draft but they both reference it since it can
also be used in client-to-mixer implementations.

We felt it was important to have actual code in there because:

* We did not find satisfactory examples in the ITU recommendations that
we are referencing.
* We would like to encourage implementation and this pretty much lifts
any audio processing background requirement from implementors.
* Although the implementation section is only informative, we still hope
it would help clear doubts during implementation and help improve
interoperability.

The code is available in two classes: an AudioLevelCalculator and an
AudioLevelRenderer. The calculator takes raw audio samples and produces
values that can then be sent with the level extensions defined in the
two drafts.

The renderer helps implementors display levels in a way that feels more
natural to users. This makes it suitable primarily to implementors of
the mixer-to-client draft. It basically cuts off values below "whisper"
and above "hearing damage" and it also ensures that level changes would
be rendered smoothly. There are of course millions of ways this part can
be improved which is why it appears separately. We felt however that it
was important to have at least a few crumbs in.

Feedback is of course most welcome and we'd love to hear from you on the
following:

* Does it make sense for you to have the code in there?
* Do you agree that the calculator and the renderer should be split the
way they are?
* Does it make sense to have the renderer code in the drafts at all?
* Do you feel the code should be improved in any way?

Cheers,
Emil

-- 
Emil Ivov                              67000 Strasbourg,
Project Lead                           France
Jitsi
[email-masked]                        PHONE: +33.1.77.62.43.30
http://jitsi.org                       FAX:   +33.1.77.62.47.31