[Mp4-tech] Re: Mp4-tech Digest, Vol 26, Issue 14

[pankaj bajpai]

Dear Michael,
Actually, all standards just tell about the bitstream syntax and decoder functioning. Some time they also give some information/suggestion for the encoder.
So, if you want to know about some specific topic regarding encoding, then you should search for journals and the best place is IEEE.
A list of tools that Simple Profile supports is as follows (if someone can add more, it will be good)
	Simple	
I/P frames
AC/DC
4MV, Unres MC
Error Resillience 
Short Header 
i am not very sure that Method 1/2 Quantization is permissible. But i think generally people use both.
Yes, Short Header mode is very similar to H.263 baseline. Infact, tools wise both are same. The only difference I find is few starting headers. In Mpeg-4, the Short video header mode and NonShort header bifurcate at VideoObjectLayer(). From this point, if it is short header mode, then video_plane_with_short_header() comes and a 22 bit start marker (short_video_start_marker) comes. This is same as Picture Start code in H.263.
However, In H.263 the bitstream start with PSC(22bit) as said above, while in MPEG-4 before coming to bifercation point some of the headers/information are also get included like Sequence start code etc.
So, this is the point where I find difference. When I implemented the Short header mode, i found decoders search for PSC. So, I concluded that in short header mode no need to dump these extra headers and my encoder works (I tested with Momusys Mpefg4 decoder and TMN H.263 decoder).
So, if someone can clarify on this point it will be very useful.
bye
Pankaj
From: Michael xjb <michael.xjb gmail.com>
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech]Help on MPEG-4 Visual issures
Date: Thu, 15 Sep 2023 23:51:10 +0800
>
> 
> Hi,Experts
> 
> Recently I begin to study the MPEG-4 Visual and need to design an
> Simple Profile codec based on MPEG-4 visual.
> 
> I try to read through the standard document(ISO/IEC JTC 1/SC 29/WG 11
> N 3056),but found it is too difficult for me to
> understand.The document seems to pay much attention on the bitstream
> syntax that encoder and decoder must conform,and does not care on how
> to implement it.
> 
> Also I could not find detailed and specific tools that are supported
> by Simple Profile.In "h.264 and MPEG-4 video compression" book(Iain
> Richardson),it is said that simple profile support (I-VOP,P-VOP,short
> header,compression efficiency tools,transmission efficiency tools) but
> with no further explain.
> 
> So,are there some other tools that also supported by Simple Profile?I
> visit the mpeg.nist.gov web but could not find related documents that
> have detailed description and specification on thoes items.Are there
> any useful documents?
> 
> There are another problem that also confusing me.In the "h.264 and
> MPEG-4 video compression" book,it is said that the short header mode
> enables the direct compatibility between MPEG-4 Simple Profile and
> H.263 baseline.What is the relationship between the two ones?Does it
> means all the tools and feature provided by H.263 baseline also
> supported by MPEG-4 Simple Profile?
> 
> 
> I am freshman on MPEG-4 visual,any help will be great for me.Please
> give me some advise,thanks in further

>
> 
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