RE: [AVT] RFC3558 header-free packet format question

["Lars-Erik Jonsson (LU/EAB)" <lars-erik.jonsson at ericsson.com>]

With frame sizes of 16, 40, 80 and 171 bits it would not be
possible to distinguish one 80 bit frame from two 40 bit frames. 

In a general case, e.g. were one wants to send multiple frames
in one packet, I believe the header-free format should not be
the one used.

Rgds,
/L-E


> -----Original Message-----
> From: Qiaobing Xie [mailto:Qiaobing.Xie at motorola.com]
> Sent: den 17 september 2004 12:39
> To: Lars-Erik Jonsson (LU/EAB)
> Cc: AVT List; adamli at icsl.ucla.edu
> Subject: Re: [AVT] RFC3558 header-free packet format question
> 
> 
> Hi, Lars-Erik/Magnus,
> 
> Thank you both for the explanation. Yes, it makes sense now. 
> Does the intended 
> ROHC-LLA/CDMA2000 operation (as described by both of you) 
> must require the 
> one-frame-per-packet limitation on the header-free format? 
> This is not obvious to me at least.
> 
> regards,
> -Qiaobing
> 
> Lars-Erik Jonsson (LU/EAB) wrote:
> 
> > Qiaobing,
> > 
> > The header-free format was included to make no-overhead-over-the-air
> > possible, then obviously assuming IP/UDP/RTP header compression on
> > the wireless link. By using RFC 3242, the header overhead can be
> > totally eliminated under certain conditions, thus one frame per RTP
> > packet can make much sense.
> > 
> > Cheers,
> > /L-E
> > 
> > 
> > 
> >>-----Original Message-----
> >>From: avt-bounces at ietf.org [mailto:avt-bounces at ietf.org]On Behalf Of
> >>Qiaobing Xie
> >>Sent: den 17 september 2004 05:51
> >>To: AVT List
> >>Cc: adamli at icsl.ucla.edu
> >>Subject: [AVT] RFC3558 header-free packet format question
> >>
> >>
> >>Hi, Adam,
> >>
> >>The text in section 4.2 of RFC3558 **seems** to indicate that 
> >>only ONE speech frame is 
> >>allowed per RTP packet when header-free format is used. This 
> >>seems to be overly limiting and 
> >>may severely hinder the usage of this payload format (e.g., I 
> >>don't think any over-the-air 
> >>link can afford to use one frame per RTP packet arrangement, 
> >>and if over-the-air link can 
> >>not use header-free format, what would be its purpose?). One 
> >>would think that as long as the 
> >>same codec rate (hence the layout and size) is in use, more 
> >>than one frame should be able to 
> >>be unambiguously carried in a header-free RTP packet.
> >>
> >>Maybe I missed something.
> >>
> >>regards,
> >>-Qiaobing
> >>
> >>
> >>_______________________________________________
> >>Audio/Video Transport Working Group
> >>avt at ietf.org
> >>https://www1.ietf.org/mailman/listinfo/avt
> >>
> > 
> > 
> 

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