[Mp4-tech] MPEG-4 compression

[Gary Sullivan]

Oops.  The first sentence should end with "only how to decode it".
-G.
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Gary Sullivan
+> Sent: Tuesday, October 28, 2023 11:19 AM
+> To: sunx; Serge GEDEON
+> Cc: bfelts envivio.com; mp4-tech lists.mpegif.org
+> Subject: RE: [Mp4-tech] MPEG-4 compression
+> 
+> 
+> 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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