Subject: [codec] #15: Efficiently combine pre-encoded audio

From: "codec issue tracker" <[email-masked]>
Date: Sun, 11 Apr 2010 15:07:56 -0000

#15: Efficiently combine pre-encoded audio
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 Reporter:  hoene@…                 |       Owner:     
     Type:  enhancement             |      Status:  new
 Priority:  minor                   |   Milestone:     
Component:  requirements            |     Version:     
 Severity:  Active WG Document      |    Keywords:     
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 Ability to efficiently combine pre-encoded audio into a single stream. For
 instance, if a server needs to play an announcement it would be nice to be
 able to send pre-encoded, cached audio data to the client in such a way
 that decoder will reset its state and decode this audio properly. Or, in
 case of conference server, to switch to another audio source without the
 need to decode and encode the audio again

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/codec/trac/ticket/15>
codec <http://tools.ietf.org/codec/>

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From: stephen botzko <[email-masked]>
Date: Sun, 11 Apr 2010 14:13:54 -0400

A related question is encoder-decoder synchronization time.  Generally audio
codecs are designed so that even if they start decoding with unknown state,
the encoder and decoder synchronize automatically and very quickly.

(Video codecs generally do not have this property BTW).

Stephen Botzko

On Sun, Apr 11, 2010 at 11:07 AM, codec issue tracker
<[email-masked]>wrote:

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From: Stephan Wenger <[email-masked]>
Date: Sun, 11 Apr 2010 12:03:56 -0700

True, with the notable exception of Vorbis (whose codebook concept is very
similar to H.264¹s parameter set concept, and the codebooks can be sent
out-of-band‹that¹s actually recommended for many applications).  See RFC
5215 how this is done.
Combining vorbis streams in a box that receives codebooks via SDP in
SIP-reinvite or something, and without in band codebooks, is an interesting
task from a synchronization viewpoint, but not impossible.
Stephan

On 4.11.2010 11:13 , "stephen botzko" <[email-masked]> wrote:

> On Sun, Apr 11, 2010 at 11:07 AM, codec issue tracker <[email-masked]>
> wrote:
>>  Reporter:  hoene@Š                 |       Owner: