RE: [rohc] Video and header compression

[khiem.le@nokia.com]

Hi,

The IR/FH, FO and SO header classification is very general, and does not
depend on whether the media is audio or video. It would be a mistake to
attempt to identify/define new kinds of headers specifically because of
video. If we take that path, God knows what other kinds of headers we will
have to introduce in the future, as new media are identified.

SO is simply defined as a header where the decompression can be done just by
knowing the RTP sequence number. Cases which require more than the sequence
number information to decompress are either FO or IR/FH. It's that simple.

Khiem

-----Original Message-----
From: EXT zhigang.liu@nokia.com [mailto:zhigang.liu@nokia.com]
Sent: Wednesday, August 09, 2000 10:14 AM
To: krister.svanbro@lu.erisoft.se; anton.martensson@era.ericsson.se;
rohc@cdt.luth.se
Subject: RE: [rohc] Video and header compression


> the primary video application target for ROHC should be one where 
> there are more than one RTP packet per video frame.

I think there is no doubt about it. 

> ... The timestamp and the Marker will change often, which the SO cannot
> handle... Perhaps we can get this from the FO format...

As I said in my previous email, using FO is the way to go. It's conceptually

consistent (with audio) and straightforward in implementation. 

Just consider the FO format for audio: it needs to have SN field, M-bit 
field, TS and/or IP-ID field. So, what are the additional things needed 
for video? None. The major differences between audio and video are NOT 
in the header format. They are TS_STRIDE (e.g. 3000 for video instead
of 240 or 160 in the case of audio) and the frequency of FO headers
(90%, or even 100%?). Please see my comments on them in my previous
email.

Zhigang
 
> Cheers, 
> 
> / Krister
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