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

[<[e-mail]>]

Yet another solution is to use AVC itself instead of SVC (you can also use RFC 3984 instead of the SVC RTP payload draft), as you need only temporal scalability. This requires the use of sub-sequence information SEI messages. The sub_seq_layer_num indicates the temporal layer. You set each sub-sequence layer (i.e. temporal layer) as one sub-sequence, then the sub_seq_frame_num indicates the frame number of each reference frame inside a temporal layer. 

In the prefix NAL unit plus PACSI with TL0PicIndex solution, the adapter needs to parse prefix NAL units, and the outcoming stream can only be of temporal_id equal to 0 (i.e. the lowest temporal layer). In the sub-seqence informtion SEI message based solution, the adapter needs to parse sub-sequence information SEI messages, and the outcoming stream can be of any lower temporal layers. 

BR, YK

>-----Original Message-----
>From: ext daniele renzi (bsoft) [mailto:[e-mail]] 
>Sent: Sunday, August 19, 2007 8:55 PM
>To: Wang Ye-Kui (Nokia-NRC/Tampere); [e-mail]; Thomas Schierl
>Cc: [e-mail]
>Subject: Re: [AVT] RTP streaming and adaptation to AVC of an 
>SVC temporal scalable bitstream - Packet loss
>
>Dear Ye-Kui, Colin, Thomas, all,
>
>many thanks for your clarifications.
>
>Anyway, I'd like to define precisely the scenario.
>Indeed, as Ye-Kui specified, the SVCtoAVC adapter assign new 
>sequence numbers to the outgoing stream.
>Here is the problem: if a packet is lost in the incoming 
>stream, it would be good if the adapter reported this anyway 
>to the receiver, even though the packet loss was in a 
>different RTP *segment* (I'm not sure if that can be defined 
>as a *session*...), as in any case there has been a loss 
>between the sender and the receiver that should be handled by 
>the receiver itself.
>But the adapter cannot say whether this loss affected the base 
>layer or an enhancement layer, as the prefix NALU could have 
>been lost and with it the scalability information 
>(temporal_id). Then it could assert that the sequence number 
>gap in the incoming stream is due to a loss in the enhancement 
>layer (then do nothing) even when this isn't true, or viceversa.
>
>We're trying to get a solution (maybe different than forcing 
>the insertion of a sequence number gap in the outgoing stream) 
>to make the receiver able to handle a loss in both the RTP *segments*.
>
>I'll try to evaluate the Thomas' proposal and have a better 
>look to RFC-3550 and draft-ietf-avt-topologies-06.txt.
>
>Thanks again.
>
>Best regards,
>
>Daniele
>
>
>Daniele Renzi
>bSoft -- www.bsoft.info
>[phone]  (tel/fax)
>
>----- Original Message -----
>From: <[e-mail]>
>To: <[e-mail]>
>Cc: <[e-mail]>; <[e-mail]>
>Sent: Sunday, August 19, 2007 7:34 AM
>Subject: RE: [AVT] RTP streaming and adaptation to AVC of an 
>SVC temporalscalable bitstream - Packet loss
>
>
>
>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: [e-mail]; [e-mail]
>>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:[e-mail]]
>>>Sent: Saturday, August 18, 2007 9:07 PM
>>>To: Wang Ye-Kui (Nokia-NRC/Tampere)
>>>Cc: [e-mail]; [e-mail]
>>>Subject: Re: [AVT] RTP streaming and adaptation to AVC of an SVC
>>>temporalscalable bitstream - Packet loss
>>>
>>>On 18 Aug 2007, at 18:36, <[e-mail]> 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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