Subject: [AVT] RFC 2190 : Clarification

From: Muni Chandra <[email-masked]>
Date: Sat, 28 Jun 2003 05:06:44 -0700 (PDT)

Hello 
 
I am working on the implementation part of RFC 2190
for H.263 video packtization.
 
I have a clarification.
 
1) As per RFC 2190, In MODE A,   beginning of Packet should contain GOB with its Header. So, this means only first GOB (or part of it) in  each packet should contain GOB header, rest GOBs will not have GOB header in the same MODE-A packet.
 
2) But H.263 standard says ( this with respective to my discussion with H.263 developers) whether all GOB's should have headers and all should not have GOB headers in a paerticular frame.
 
3) So to acheive above point 1 with respective above point 2, we need to  calculate header for all GOB's and transmit GOB header only for first GOB of each MODE - A packet.
 
Please clarify above point 3 is correct or we can calculate GOB headers for only first GOB of each MODE -A packet. So that we can save time of GOB header computation at  rest of GOBs.
 
Thanking you in Advance
 
Muni Chanra Reddy

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---

From: "Gary Sullivan" <[email-masked]>
Date: Mon, 30 Jun 2003 12:03:35 -0700

A few comments in response:
 
- RFC 2190 should only be used for H.263 that pre-date 1998 in syntax
design (i.e., no use of PLUSPTYPE header format).
 
- RFC 2429 is a better design than 2190, and 2429 can be used for both
old and newer versions of H.263 syntax.
 
Regarding the questions:
 
1) I don't think RFC 2190 any prohibition against having additional GOB
headers within Mode A packets.  The RFC says it "allows fragmentation at
GOB boundaries", but I don't see anywhere where it says it *requires*
such fragmentation or prohibits GOB headers within packets.
 
2) As far as the H.263 standard (and within RFC 2190, I believe) is
concerned, it is up to the discretion of the encoder when to send GOB
headers and when not to.  Even within a single coded picture, some GOBs
can have headers while others do not.  In some particular system
environments (e.g. in some H.32x environments), there are ways to
indicate that GOB headers should be sent or do not need to be sent for
all GOBs - but this is outside the scope of H.263 itself.  There is
nothing in the H.263 video spec itself that requires any particular
behavior for whether GOB headers are present or not.
 
3) Given the above statements about item 1, I don't think item 3 is
especially relevant anymore.
 
Best Regards,
 
Gary Sullivan
 
 -----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Muni
Chandra
Sent: Saturday, June 28, 2003 5:07 AM
To: [email-masked]
Subject: [AVT] RFC 2190 : Clarification

Hello 

I have a clarification.
 
1) As per RFC 2190, In MODE A,   beginning of Packet should contain GOB
with its Header. So, this means only first GOB (or part of it) in  each
packet should contain GOB header, rest GOBs will not have GOB header in
the same MODE-A packet.
 
2) But H.263 standard says ( this with respective to my discussion with
H.263 developers) whether all GOB's should have headers and all should
not have GOB headers in a paerticular frame.
 
3) So to acheive above point 1 with respective above point 2, we need to
calculate header for all GOB's and transmit GOB header only for first
GOB of each MODE - A packet.
 
Please clarify above point 3 is correct or we can calculate GOB headers
for only first GOB of each MODE -A packet. So that we can save time of
GOB header computation at  rest of GOBs.
 
Thanking you in Advance
 
Muni Chanra Reddy

  _____  

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