[Speex-dev] Re: One bug in the SVN and rtp wrapper issue

[Jean-Marc Valin]

> 1) First, I think there is a bug in  libspeex/lsp.c  line 512.
> 
> /* hard limit ak's to +/- 32767 */
>       if (a < -32767) a =32767;   // This line should be changed to if
> (a < -32767) a = -32767;
>       if (a > 32767) a = 32767;
>       ak[j-1] = (short)a;

Oops. Thanks for pointing that out. It's fixed in svn.

> 2) About the RTP wrapper for VoIP
> 
> I'd like to use the payload format defined in the SVN document rtp.txt
> as below.
> 
> What I'm worry about is the interoperability with other implementations.
> 
> What's your opinion on that?

Can you summarize what the issue is?

	Jean-Marc

> Best Regards,
> 
> Lianghu
> 
> 
> //************************from the SVN /doc/rtp.txt begin
> *************************************//
> The Speex RTP payload is defined as a header, followed by any number of
> requests to the remote encoder and all encoded speech frames.
> 
> +--------+----------+----------------+
> | Header | Requests | Speech data... |
> +--------+----------+----------------+
> 
> The header contains only the number of frames sent
> encoded in 6 bits
> 
>  0 1 2 3 4 5
> +-+-+-+-+-+-+
> | NB frames |
> +-+-+-+-+-+-+
> 
> There can be any number of requests of the form
> 
>  0 1 2 3 4 5 6 7 0 1
> +-+-+-+-+-+-+-+-+-+-+
> |R| ReqID | ReqVal  |
> +-+-+-+-+-+-+-+-+-+-+
> 
> where R is 1 when a request is following and 0 when there is no more
> request. Each request (if R=1) is composed of a 4-bit request ID (ReqID) and
> a 5-bit value (ReqVal)
> 
> Possible values for ReqID are:
>  0: REQ_PERSIST   ReqVal=1 for persistent requests/mode selection,
>                   0 otherwise
>  1: PERSIST_ACK   Acknowledge a REQ_PERSIST from the other end,
>                   ReqVal equals the value received
>  2: MODE          Choose the encoder mode directly
>  3: QUALITY       Choose the encoder quality
>  4: VBR           Set VBR on (ReqVal=1) or off (ReqVal=2)
>  5: VBR_QUALITY   Set the encoder quality for VBR mode
>  6: LOW_MODE      Set the encoder mode for low-band (wideband only)
>  7: HIGH_MODE     Set the encoder mode for high-band (wideband only)
> 
> All requests should be considered at the receiver as a suggestion and
> compliance is not mandatory. The PERSIST_ACK should be sent upon receiving a
> REQ_PERSIST request to indicate that the request has been received.
> 
> The speech data part contains speech frames one after the other. The size of
> the encoded frames can be found since the mode is directly encoded into each
> frame.
> 
> For example, a frame where we request VBR to be on with quality 8 and we
> transmit two frames encoded at 8.35 kbps (167 bits/frame) will be:
> 
>  0               1               2               3
>  0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |   NB=2    |1|ReqID=2| ReqVal=0|1|ReqID=3|ReqVal=8 |0| frame 1 |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 1                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 1                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 1                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 1                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 1                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |end|                     frame 2                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 2                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 2                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 2                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |                         frame 2                               |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |    end frame 2    |P|P|P|P|P|P|
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
> //************************from the SVN /doc/rtp.txt end
> *************************************//