RE: [AVT] RTP streaming and adaptation to AVC of an SVC temporalscalable bitstream - Packet loss

[<Ye-Kui.Wang at nokia.com>]

OK, forget about my naïve question, because I found the following sentence in RFC 3550, "If multiple data packets are re-encoded into one, or vice versa, a translator MUST assign new sequence numbers to the outgoing packets." 

BR, YK 

>-----Original Message-----
>From: Wang Ye-Kui (Nokia-NRC/Tampere) 
>Sent: Sunday, August 19, 2007 12:59 AM
>To: 'ext Colin Perkins'
>Cc: daniele at bsoft.info; avt at ietf.org
>Subject: RE: [AVT] RTP streaming and adaptation to AVC of an 
>SVC temporalscalable bitstream - Packet loss
>
>
>Hi Colin, 
>
>Thanks for your clarification. But according to the following 
>sentence copied from Daniele's email, 
>
>"... then the SVCtoAVC adapter doesn't know whether this loss 
>has to be signaled to the receiver, i.e. whether it must 
>insert a sequence number gap in the outcoming RTP stream...", 
>
>the SVCtoAVC adapter uses a different RTP sequence number 
>value space for the outcoming RTP steam than the incoming RTP 
>stream. Is this what a translator can do? It is not clear how 
>the SVCtoAVC adapter handles the CC, SSRC and CSRC fields and 
>RTCP traffic, though. 
>
>BR, YK
>
>>-----Original Message-----
>>From: ext Colin Perkins [mailto:csp at csperkins.org]
>>Sent: Saturday, August 18, 2007 9:07 PM
>>To: Wang Ye-Kui (Nokia-NRC/Tampere)
>>Cc: daniele at bsoft.info; avt at ietf.org
>>Subject: Re: [AVT] RTP streaming and adaptation to AVC of an SVC 
>>temporalscalable bitstream - Packet loss
>>
>>On 18 Aug 2007, at 18:36, <Ye-Kui.Wang at nokia.com> wrote:
>>> In your example the SVCtoAVC adapter is an RTP mixer, which
>>terminates
>>> the RTP session between the sender and itself and restarts
>>another RTP
>>> session between itself and the receiver.
>>> Therefore the RTP sequence number needs to be updated for the base 
>>> layer packets anyway.
>>
>>If the SVCtoAVC adapter is a transcoder from an SVC stream to an AVC 
>>stream, it will be an RTP translator, not an RTP mixer.
>>Neither an RTP translator or a RTP mixer terminate the RTP 
>session. RFC 
>>3550 and draft-ietf-avt-topologies-06.txt discuss this in more detail.
>>
>>--
>>Colin Perkins
>>http://csperkins.org/
>>
>>
>>

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