Re: [codec] #28: Layered bit-stream

"Christian Hoene" <hoene@uni-tuebingen.de> Wed, 05 May 2010 19:02 UTC

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From: Christian Hoene <hoene@uni-tuebingen.de>
To: 'Vladimir Sviridenko' <vladimirs@spiritdsp.com>, codec-bounces@ietf.org
References: <5A3D7E7076F5DF42990A8C164308F8107884A0@mail-srv.spiritcorp.com> <5A3D7E7076F5DF42990A8C164308F8107FB29E@mail-srv.spiritcorp.com> <5A3D7E7076F5DF42990A8C164308F8107FB29F@mail-srv.spiritcorp.com> <5A3D7E7076F5DF42990A8C164308F8107FB2A7@mail-srv.spiritcorp.com>
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Date: Wed, 05 May 2010 21:01:56 +0200
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Cc: 'Dmitry Yudin' <Yudin@spiritdsp.com>, 'Slava Borilin' <Borilin@spiritdsp.com>, codec@ietf.org
Subject: Re: [codec] #28: Layered bit-stream
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Hi Vladimir,

>2/ we think that VoIP and Videoconferencing systems are users of such
>codecs.

Could you please explain your position a bit?

As far as I understand, layered coding helps if multiple streams having the sample content but different rates must be generated.
For example, if a conferencing system stream the same audio stream to N users but each users has a different bandwidth. Just encode
all layers and drop the higher layers for the low bandwidth users. This approach is easy and efficient and reduce the encoding
complexity.

The arguments against are simple. 
a) First, this use case is a local optimization only. Thus, the must not be standardized.
b) Second, instead of layered coding one can use other ways of tweaking the implementation performance. For example, if you
calculate a 512 FFT do get two 256 FFTs for free. I bet there are thousand other shortcuts which I am not aware of.

Thus, I have the opinion that layered coding is not worth the extra bandwidth of 20 or more percentage. It is just good locally but
not needed for interoperability.

Yours,

 Christian






>Yours,
>Vladimir Sviridenko
>SPIRIT
>
>-----Original Message-----
>From: codec-bounces@ietf.org [mailto:codec-bounces@ietf.org] On Behalf
>Of codec issue tracker
>Sent: Sunday, May 02, 2010 5:10 PM
>To: hoene@uni-tuebingen.de
>Cc: codec@ietf.org
>Subject: [codec] #28: Layered bit-stream
>
>#28: Layered bit-stream
>------------------------------------+-----------------------------------
>----
> Reporter:  hoene@...                 |       Owner:
>     Type:  defect                  |      Status:  new
> Priority:  minor                   |   Milestone:
>Component:  requirements            |     Version:
> Severity:  Active WG Document      |    Keywords:
>------------------------------------+-----------------------------------
>----
> Shall layered coding be supported?
> Who needs it?
> Can we drop this requirement?
>
>--
>Ticket URL: <http://trac.tools.ietf.org/wg/codec/trac/ticket/28>
>codec <http://tools.ietf.org/codec/>
>
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