[Speex-dev] "Redundant audio data" header in speex payload

[Emmanuel Wauters]

Yes, it is possible that the audio is stationary.
But I want to point out here that it's not me who is doing the 
interpretation, but the parser in wireshark.

Here is a snippet of its message output:
Real-Time Transport Protocol
   10.. .... = Version: RFC 1889 Version (2)
   ..0. .... = Padding: False
   ...0 .... = Extension: False
   .... 0000 = Contributing source identifiers count: 0
   0... .... = Marker: False
   Payload type: Unknown (99)
   Sequence number: 54956
   Timestamp: 3107650972
   Synchronization Source identifier: 1061405506
RFC2198: Redundant Audio Data
   Header 1: PT=Unknown (41)
       0... .... = Follow: Not set
       .010 1001 = Payload type: 41
   Payload: D9C99D8F2EC774B445B9BD5318A33790B7079BE5E042A59F... 

Emmanuel

Jean-Marc Valin wrote:

>Keep in mind that Speex doesn't know about RTP, networks, files or
>anything like that. So the byte you're seeing is either added by the
>client, or else it happens that Speex produces a byte that you're
>misinterpreting as to mean something else. A normal Speex CBR Speex
>stream always has the first 5 bits set to the same value (indicating the
>mode), so maybe the audio is stationary enough for the next three bits
>to be constant as well?
>
>	Jean-Marc
>
>Emmanuel Wauters a écrit :
>  
>
>>In attachement a trace of two speex streams, one going from my machine
>>(172.17.10.16) to a transcode process (172.17.21.31) and another one
>>going vice versa (ssrc 1238454564). The aim for the transcode process is
>>to decode the speex packets, encode the data back again and send it back
>>to the origin.
>>
>>I noticed that the payload data of a stream (in either direction) always
>>had the same first byte,
>>and in the wireshark packet grabber, this byte is parsed as a "Redundant
>>Audio Data" (rfc 2198) header with values 41 (first stream) and 46
>>(reverse stream).
>>What I want to know is if this header must be the same in both
>>directions, so that this header might be handled wrongly now in the
>>transcode process. If it is wrong, then I want to know if I can change
>>the value of it through the speex api.
>>
>>
>>Thanks,
>>Emmanuel
>>
>>Jean-Marc Valin wrote:
>>
>>    
>>
>>>Can you explain a bit more what you mean and what you want to know?
>>>
>>>    Jean-Marc
>>>
>>>Emmanuel Wauters a écrit :
>>> 
>>>
>>>      
>>>
>>>>Hi,
>>>>
>>>>Has anybody some information on on the "Redundant audio data" header in
>>>>the speex rtp payload?
>>>>Is this header always present? Is its value always the same?
>>>>Can it be modified through some speex_*_ctl function?
>>>>
>>>>Thanks,
>>>>Emmanuel
>>>>
>>>>  
>>>>        
>>>>
>>> 
>>>
>>>      
>>>
>>    
>>
>
>  
>


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