Subject: [AVT] TFRC with audio + video

From: Alejandro Cabrera Obed <[email-masked]>
Date: Tue, 16 Aug 2005 15:25:14 -0300

Hi people, 

I know Ladan Gharai is currently working in the tansmission of audio +
video in HDTV, but  need to ask for your opinion about this topic.

Suppose I send HDTV uncompressed (audio + video), using two RTP
sessions, and I apply the "RTP profile for TFRC" for both streams
independently. So, I have the following:
 
- one RTP payload format for uncompressed video
- one RTP payload format for audio
- one RTP profile for TFRC applied to the video session
- one RTP profile for TFRC applied to the audio session

(Logically I need to synchronize the two flows in order to get
lyp-synchronization).

In the reception side I want to use a jitter buffer of 10 seconds for
the video in order to hide the througput variations and to measure the
buffer underflow to dowsampling the video rate in this case.....but
here is my question: what about the jitter buffer for the audio ???
Can it be the same as the video one or it has to be another buffer ???
Does it affect the video buffer underflow measuring ???

Thanks a lot for your great help as always !!!

Alejandro

-- 
Alejandro Cabrera Obed
[email-masked]

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 22 Aug 2005 16:36:40 +0200

Hi,

Yes, you will need to buffer also the audio (assuming that audio and 
video are sent in sync). With two different stream contexts in TFRC you 
will need to buffer both media sufficient to be able to play out them in 
sync. Thus it may end up that the amount of media in the buffers for 
audio and video could vary widely, especially if the transmitting side 
do buffer some duration to handle minor variations in rate. This would 
of course result in that audio and video are not sent in sync, however 
that is definitely possible and something that do occur in certain 
streaming systems.

Cheers

Magnus

-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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