advanced video compression - part 2.mht

mpeg test inter b. Dequantizer Algorithm hardware realization method and comparison c. Dequantize

have been=20
            completely changed. But for our purposes, it's good enough =
to say=20
            that MPEG2 is a souped-up version of MPEG1 with support for=20
            Interlaced video and High-res pictures.</P>
            <P><B>Benefits:</B> MPEG2 gives better picture quality than =
MPEG1 at=20
            full CCIR 601 resolution (720x480) and at comparable =
bitrate.=20
            Basically, MPEG2 scales, while MPEG1 doesn't.</P>
            <P><B>Disadvantages:</B> MPEG2 takes more CPU horsepower to=20
            decompress, and basically has no advantage over MPEG1 at =
lower=20
            resolutions. If you're distributing for the web, you're not =
going to=20
            want to be compressing stuff in MPEG2 instead of MPEG1 =
because the=20
            benefits of MPEG2 aren't realized until you get into full TV =

            resolution, which means big filesizes. Additionally, most =
operating=20
            systems don't support MPEG2 playback right out of the box, =
while=20
            they do for MPEG1.</P>
            <P><B>Recommendation:</B> If you're creating your own =
high-quality=20
            archival backups of your videos, I would encode them at =
DVD-quality=20
            MPEG2, but I would never use MPEG2 for online distribution. =
If you=20
            are submitting your video to a convention, MPEG2 is =
typically=20
            recommended.<BR><BR></P></TD></TR>
        <TR>
          <TD vAlign=3Dtop><B>3)</B></TD>
          <TD><B>DivX</B>=20
            <P><B>Origins:</B> (adapted from <A=20
            href=3D"http://en.wikipedia.org/">Wikipedia</A> article on =
<A=20
            href=3D"http://en.wikipedia.org/wiki/DivX">DivX</A>) =
<BR>DivX ;-) 3.11=20
            Alpha and earlier versions generally refer to a hacked =
version of=20
            the Microsoft MPEG-4 Version 2 video codec, extracted around =
1998 by=20
            French hacker Jerome Rota (also known as Gej). The Microsoft =
codec,=20
            which originally required that the compressed output be put =
in an=20
            ASF file (the precursor to Windows Media), was altered to =
allow=20
            other containers such as AVI. From 1998 through 2002, =
independent=20
            enthusiasts within the DVD-ripping community created =
software tools=20
            which dramatically enhanced the quality of video files that =
the DivX=20
            ;-) 3.11 Alpha codec could produce. One notable tool is =
Nandub, a=20
            modification of the open-source VirtualDub, which features =
two-pass=20
            encoding (termed "Smart Bitrate Control" or SBC) as well as =
access=20
            to internal codec features. In early 2000, Rota created a =
company=20
            (originally called DivXNetworks, Inc., renamed to DivX, Inc. =
in=20
            2005) to improve DivX and steward its development. The =
company=20
            released a new version of the codec as DivX 4.0 in July =
2001. DivX 4=20
            was no longer a hack of a Microsoft codec, but was designed=20
            completely from scratch. It is worth noting, however, that =
DivX 4.0=20
            actually began as the result of the work of many open-source =

            developers back when it was known as the "OpenDivX" project. =
However=20
            when the page was pulled and the source was closed to become =
the=20
            commercial DivX 4.0, many of the unpaid and unacknowledged=20
            developers saved the last CVS snapshot of the OpenDivX code =
and from=20
            there worked to create XviD, rivaling DivXNetworks' =
commercial=20
            efforts. Regardless, DivX, Inc. has been granted patents on =
parts of=20
            the DivX codec, which is fully MPEG-4-Advanced Simple =
Profile=20
            compliant. The next major version, DivX 5.0, was released in =
March=20
            2002. A further improved version, DivX 6, was released on 15 =
June=20
            2005.</P>
            <P><B>Benefits:</B> Although previous versions of DivX =
always=20
            struggled to achieve the same quality as XviD, DivX 6 is =
quite on=20
            par with it. The codec is quite simple to set up and use. =
DivX does=20
            have very good playback options for PC, Linux, and the Mac, =
which=20
            covers the three biggest desktop platforms.</P>
            <P><B>Disadvantages:</B> It's a commercial codec, so in =
order to get=20
            all the options you have to pay money for it. There is a =
free=20
            version that limits the options you can use, but then the =
quality=20
            will suffer significantly. Considering that XviD is free and =
has=20
            comparable quality to the full version of DivX, it really =
doesn't=20
            make sense to pay for this codec.<BR></P>
            <P><B>Recommendation:</B> Just pass this one up in favor of =
XviD.=20
            You really aren't missing anything.</P><BR></TD></TR>
        <TR>
          <TD vAlign=3Dtop><B>4)</B></TD>
          <TD><B>XviD</B>=20
            <P><B>Origins:</B> When OpenDivX closed its source and went =
on to=20
            produce DivX4, a group of open source developers decided to =
take the=20
            code that was left from OpenDivX and start their own codec. =
Thus=20
            XviD (or DivX backwards) was born. By now very little of the =

            original OpenDivX code remains but there's a few bits here =
and=20
            there.</P>
            <P><B>Benefits:</B> XviD has all sorts of tweakable options, =
which=20
            means an experienced encoder (or one following a =
well-written guide)=20
            can produce some very nice looking encodes. It can also =
produce=20
            MPEG4 compatible streams if you want to distribute as .MP4 =
files.=20
            Thanks to the proliferation of the MPEG4 standard it is =
possible to=20
            play XviD encodes on almost any platform you can think =
of.<BR></P>
            <P><B>Disadvantages:</B> Unlike DivX, it can be difficult to =
setup=20
            at first glance. Not much =
else...<BR><BR><B>Recommendation:</B> This=20
            is currently one of the most used codecs for distributing =
AMVs. It=20
            provides excellent quality and compressibility as well as =
advanced=20
            features, and it has good cross-compatibility amongst =
desktop=20
            operating systems. Highly recommended.<BR><BR></P></TD></TR>
        <TR>
          <TD vAlign=3Dtop><B>5)</B></TD>
          <TD vAlign=3Dtop><B>Windows Media Video 9 </B>
            <P><B>Benefits: </B>A very competent codec indeed, on par =
with and=20
            possibly even slightly surpassing XviD in quality. </P>
            <P><B>Disadvantages: </B>Of course, its proprietary nature =
fails it,=20
            and it is not MPEG4 compatable. Not many options are exposed =
for you=20
            to tweak. This codec is generally found in the Windows Media =

            container, rather than AVI, so it may be looked down upon =
for that.=20
            Also, the majority of people who encode to WMV9 tend to =
produce=20
            small, low-quality files, which tends to give the codec a =
bad name.=20
            While its certainly capable of very high quality, people =
will just=20
            generally assume that a WMV file is low quality.</P>
            <P><B>Recommendations: </B>While Windows Media Video 9 is =
capable of=20
            pretty nice quality, it generally has no significant =
advantage over=20
            XviD to really warrant its use. XviD is just generally =
better=20
            accepted. <BR><BR></P></TD></TR>
        <TR>
          <TD vAlign=3Dtop><B>6)</B></TD>
          <TD><B>x264</B>=20
            <P>What it is: x264 is a freely available open source =
implementation=20
            of the h.264 standard. H.264, or AVC as it is sometimes =
known is a=20
            very advanced compression method that is part of the MPEG-4=20
            standard.</P>
            <P><B>Benefits:</B> This simply offers the best quality at =
the=20
            smallest filesize, bar none. XviD can't even come close to =
what this=20
            codec can achieve!</P>
            <P><B>Disadvantages:</B> In order to take full advantage of =
this=20
            codec, it should be used with the MPEG-4 container. That =
makes one=20
            more thing that users may have to install in order to play =
your=20
            video. Probably the biggest disadvantage of x264 (or any =
h.264 codec=20
            for that matter) is that it can take quite a bit of CPU =
power to=20
            play back. If you use this codec, viewers on slow computers =
may not=20
            be able to watch your video!</P>
            <P><B>Recommendations:</B> If you want the absolute best =
quality to=20
            filesize ratio, then this is your best choice. Just keep in =
mind=20
            that you may be cutting off potential viewers by using this =
right=20
            now. This is continuing to gain popularity and is now =
starting to=20
            come into widespread use. If you don't mind the current=20
            disadvantages, this is highly recommended. <BR>
            <P class=3Dbyline align=3Dright>ErMaC, AbsoluteDestiny and =
Zarxrax -=20
            September 2006<BR></P></TD></TR></TBODY></TABLE>
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