[xiph-rtp] header ident decision

[Phil Kerr]

Ralph Giles wrote:

>On Sun, May 01, 2005 at 09:52:56AM -0700, Ralph Giles wrote:
>
>  
>
>>One this I think we can define is in-band transmission. Just send the
>>header packets in the RTP stream like they were any other type. The 
>>16 bit setup ident field of the header packets must match the setup 
>>ident of the data packets that rely on them. In the default case the 
>>three standard headers are sent at the beginning of the stream, just
>>as they are in Ogg. The server MAY also retransmit the headers 
>>periodically; clients MUST handle such header packets when they occur.
>>    
>>
>
>Some further clarification from discussion with Aaron on IRC:
>
>Clients MUST handle any header packet at any point in the RTP stream; 
>there is no restriction on ordering or grouping. When using in-band 
>transmission, the server SHOULD send the initial 3 header packets, in 
>order, at the beginning of the stream, including the comment header even 
>if it contains only the required vendor string from the encoder.
>  
>
This is detailed in the current specification.

>The server MUST ensure that the setup ident field in the payload header 
>attached to any ident or setup header packets is a consistent and unique 
>mapping within an RTP session, so that clients can safely discard such 
>packets if they already have a decode setup for that ident field.
>  
>
Because the Ident field is freeform (not derived from the stream itself 
using crc32) you will lose caching.

>The server MAY choose to send multiple comment packets with the same 
>ident field value. Such packets, when received, indicate to the client 
>that the new set of metadata applies to the audio data that follows. 
>
This is detailed in the current specification.

-P

>
> -r
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