[Mp4-tech] MPEG-4 compression

[Gary Sullivan]

One thing to keep in mind is that standards do not specify how to encode
video -- only how to encode it.  There is a great deal of freedom
provided in the standards that allows encoding designs of vastly
differing quality.  You should never look at the quality decoded from
some particular implementation of an encoder using a particular standard
and assume that this quality is the only quality (or the best quality)
that is possible to obtain when using that standard.  You should
definitely not expect the quality produced by all products to be the
same.  Not only is there freedom allowed in the design of pre-processors
and encoders but there is also freedom allowed in post-processing and
display aspects after decoding.
Another aspect implicit in Sunx's response is that there are a number of
different syntaxes that fall under the term "MPEG-4 video".  There are
somewhere around 20 profiles in MPEG-4 part 2 and three profiles in
MPEG-4 part 10.  For ordinary camera-view video, the most efficient
syntax design currently in MPEG-4 is in the Main profile of MPEG-4 part
10 (a.k.a. AVC a.k.a. ITU-T H.264).  Serge did not specify which profile
was implemented in that Envivio product.
And of course the RealNetworks codec that Serge referred to is not even
constrained by conformance to any standard.  The quality it produces is
constrained only by the product's implementation resources, the
expertise of its designers, and the deadlines of its design project.
Best Regards,
-Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of sunx
+> Sent: Tuesday, October 28, 2023 8:35 AM
+> To: Serge GEDEON
+> Cc: bfelts envivio.com; mp4-tech lists.mpegif.org
+> Subject: Re: [Mp4-tech] MPEG-4 compression
+> 
+> 
+> 
+> 
+> On Tue, 28 Oct 2003, Serge GEDEON wrote:
+> 
+> > Dear All,
+> >
+> > I am currently comparing different compression solutions 
+> for streaming pedagogical multimedia contents over the Internet.
+> >
+> > But with the software I am using (Envivio coding station 
+> 2.1) to encode MPEG-4 content,
+> > I can't reach the same quality with the same bitrate as 
+> with Real 9. Real 9 compression is better, the thing that I 
+> find a bit odd.
+> >
+> > Could anyone help me in this? did anyone do such a 
+> comparison? may it be the soft that I am using? could anyone 
+> advise me with another soft?
+> > or may it be the parameters that I am using, I ve tryed 
+> aproximatly all the combinations possible!!!
+> >
+> 
+> I believe one major reason that MPEG-4 is better than MPEG-2 
+> is that it
+> has better motion compensated coding, which is especially 
+> true in H.264.
+> My suggestion is that maybe you need to tune those paramters 
+> of control
+> PVOP and BVOP coding carefully. Real format is modified from 
+> MPEG-2 (?),
+> so MPEG-4 should at least achieve the comparative performance in most
+> cases.
+> 
+> >
+> > Thanks in advance,
+> > Serge GEDEON
+> > Ph.D. Student
+> > Paul Sabatier University - Toulouse, France
+> 
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