Re: [Ccrtp-devel] Payload padding

[Federico Montesino Pouzols]

Hi, 

you are right, padding is not mandatory for data packets. It is a bug
in ccrtp. I would propose a new method, say setPadding, with an
integer parameter 'p' to set padding to a multiple of 'p'. 0 (no
padding) would be a good default value.

Thanks for spotting this.

On Sat, Jan 08, 2005 at 04:50:46PM +0100, Michel de Boer wrote:
> Hi,
> 
> I am using ccrtp 1.1.2 to send and receive a GSM encoded voice stream. 
> The size
> of a single GSM encoded payload is 33 bytes. I noticed that ccrtp adds 3 
> bytes padding
> to make the payload a multiple of 4 and sets the P-bit in the RTP headers.
> 
> I have seen this topic before in this mailing list and then it was said 
> that the RFC requires
> the padding. That is not true.
> 
> RFC 3550 only requires padding to a multiple of 4 for header 
> information. Payloads do not
> have to be padded. The padding of a payload may only be needed for 
> certain encryption
> schemes. Here is what RFC 3550 says:
> 
>   padding (P): 1 bit
>      If the padding bit is set, the packet contains one or more
>      additional padding octets at the end which are not part of the
>      payload.  The last octet of the padding contains a count of how
>      many padding octets should be ignored, including itself.  Padding
>      may be needed by some encryption algorithms with fixed block sizes
>      or for carrying several RTP packets in a lower-layer protocol data
>      unit.
> 
> For my own purpose I have disabled padding in my own copy of ccrtp in 
> the RTPPacket
> constructor.
> 
> I think it would be good if payload padding would be optional in a next 
> version. By
> default I would prefer the padding to be disabled.
> 
> Regards,
> Michel
> 
> 
> 
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