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

Emmanuel Wauters emmanuel.wauters at androme.com
Fri Mar 2 03:23:20 PST 2007


In attachement two messages 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

First packet:
--------------
No.     Time                       Source                
Destination           Protocol Info
      1 2007-03-02 10:11:02.135207 172.17.10.16          
172.17.21.31          RTP      Payload type=Unknown (99), 
SSRC=1061405506, Seq=54956, Time=3107650972

Frame 1 (92 bytes on wire, 92 bytes captured)
    Arrival Time: Mar  2, 2007 10:11:02.135207000
    [Time delta from previous packet: 0.000000000 seconds]
    [Time since reference or first frame: 0.000000000 seconds]
    Frame Number: 1
    Packet Length: 92 bytes
    Capture Length: 92 bytes
    [Frame is marked: False]
    [Protocols in frame: eth:ip:udp:rtp:rtp]
    [Coloring Rule Name: UDP]
    [Coloring Rule String: udp]
Ethernet II, Src: 3Com_d2:51:74 (00:04:76:d2:51:74), Dst: Intel_eb:49:49 
(00:0c:f1:eb:49:49)
    Destination: Intel_eb:49:49 (00:0c:f1:eb:49:49)
        Address: Intel_eb:49:49 (00:0c:f1:eb:49:49)
        .... ...0 .... .... .... .... = Multicast: This is a UNICAST frame
        .... ..0. .... .... .... .... = Locally Administrated Address: 
This is a FACTORY DEFAULT address
    Source: 3Com_d2:51:74 (00:04:76:d2:51:74)
        Address: 3Com_d2:51:74 (00:04:76:d2:51:74)
        .... ...0 .... .... .... .... = Multicast: This is a UNICAST frame
        .... ..0. .... .... .... .... = Locally Administrated Address: 
This is a FACTORY DEFAULT address
    Type: IP (0x0800)
Internet Protocol, Src: 172.17.10.16 (172.17.10.16), Dst: 172.17.21.31 
(172.17.21.31)
    Version: 4
    Header length: 20 bytes
    Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
        0000 00.. = Differentiated Services Codepoint: Default (0x00)
        .... ..0. = ECN-Capable Transport (ECT): 0
        .... ...0 = ECN-CE: 0
    Total Length: 78
    Identification: 0x6672 (26226)
    Flags: 0x00
        0... = Reserved bit: Not set
        .0.. = Don't fragment: Not set
        ..0. = More fragments: Not set
    Fragment offset: 0
    Time to live: 128
    Protocol: UDP (0x11)
    Header checksum: 0x5cdb [correct]
        [Good: True]
        [Bad : False]
    Source: 172.17.10.16 (172.17.10.16)
    Destination: 172.17.21.31 (172.17.21.31)
User Datagram Protocol, Src Port: 23010 (23010), Dst Port: 40632 (40632)
    Source port: 23010 (23010)
    Destination port: 40632 (40632)
    Length: 58
    Checksum: 0x8447 [correct]
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...

No.     Time                       Source                
Destination           Protocol Info
      3 2007-03-02 10:11:02.136042 172.17.21.31          
172.17.10.16          RTP      Payload type=Unknown (99), 
SSRC=1238454564, Seq=979, Time=300591171


Second packet:
----------------
Frame 3 (92 bytes on wire, 92 bytes captured)
    Arrival Time: Mar  2, 2007 10:11:02.136042000
    [Time delta from previous packet: 0.000274000 seconds]
    [Time since reference or first frame: 0.000835000 seconds]
    Frame Number: 3
    Packet Length: 92 bytes
    Capture Length: 92 bytes
    [Frame is marked: False]
    [Protocols in frame: eth:ip:udp:rtp:rtp]
    [Coloring Rule Name: UDP]
    [Coloring Rule String: udp]
Ethernet II, Src: Intel_eb:49:49 (00:0c:f1:eb:49:49), Dst: 3Com_d2:51:74 
(00:04:76:d2:51:74)
    Destination: 3Com_d2:51:74 (00:04:76:d2:51:74)
        Address: 3Com_d2:51:74 (00:04:76:d2:51:74)
        .... ...0 .... .... .... .... = Multicast: This is a UNICAST frame
        .... ..0. .... .... .... .... = Locally Administrated Address: 
This is a FACTORY DEFAULT address
    Source: Intel_eb:49:49 (00:0c:f1:eb:49:49)
        Address: Intel_eb:49:49 (00:0c:f1:eb:49:49)
        .... ...0 .... .... .... .... = Multicast: This is a UNICAST frame
        .... ..0. .... .... .... .... = Locally Administrated Address: 
This is a FACTORY DEFAULT address
    Type: IP (0x0800)
Internet Protocol, Src: 172.17.21.31 (172.17.21.31), Dst: 172.17.10.16 
(172.17.10.16)
    Version: 4
    Header length: 20 bytes
    Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
        0000 00.. = Differentiated Services Codepoint: Default (0x00)
        .... ..0. = ECN-Capable Transport (ECT): 0
        .... ...0 = ECN-CE: 0
    Total Length: 78
    Identification: 0x09a8 (2472)
    Flags: 0x00
        0... = Reserved bit: Not set
        .0.. = Don't fragment: Not set
        ..0. = More fragments: Not set
    Fragment offset: 0
    Time to live: 64
    Protocol: UDP (0x11)
    Header checksum: 0xf9a5 [correct]
        [Good: True]
        [Bad : False]
    Source: 172.17.21.31 (172.17.21.31)
    Destination: 172.17.10.16 (172.17.10.16)
User Datagram Protocol, Src Port: 40632 (40632), Dst Port: 23010 (23010)
    Source port: 40632 (40632)
    Destination port: 23010 (23010)
    Length: 58
    Checksum: 0xe820 [correct]
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: 979
    Timestamp: 300591171
    Synchronization Source identifier: 1238454564
RFC2198: Redundant Audio Data
    Header 1: PT=Unknown (46)
        0... .... = Follow: Not set
        .010 1110 = Payload type: 46
    Payload: 8E701C7FEE8F9B92D60A329AA71BF8CB20C0F07DFF9BDC05...

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
>>
>>    
>>
>
>  
>


-- 

-------------------------------------------------------------
Emmanuel Wauters                      Tel : (+32) 11 30 13 30           
mailto:emmanuel.wauters at androme.com   http://www.androme.be
ANDROME NV
Wetenschapspark 4
B-3590 Diepenbeek, Belgium  



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