[geeks] Whee! Lightning strikes, AGAIN!

[gsm at mendelson.com]

On Wed, Jul 29, 2009 at 11:32:07AM -0400, Joshua Boyd wrote:
>I'm not sure what this has to do with why YUV potentially requires less
>bandwidth than RGB.

It may not. I was explaining what MPEG encoding was. RGB can be as good
or bad depending upon the compression method.  As you say later, the
choice of compression method is limited by how fast you can decode it, or:
  
>Certainly you can do better with extra smarts like you suggest, and
>MPEG2 allows that, but in the real world if you take that very far you
>get video that only be played back by a limited subset of PC based
>decoders.  

Unless you make a standard decoding platform and include the codec in
the media. 


>Also, I feel like you skip massive important details like motion
>compensation and macroblock compression.

Not on purpose to hide anything, but to limit the amount of text I wrote.
Eventually even the people who hang on my every word in my wonderful 
postings to geeks get bored and hit delete.

Hello, hello, is there anyone still there??? :-)

>That said, a really smart encode is still limited by how stupid many
>decoders are, and as such, a fixed pattern of I frames (key frames) and
>non I frames is often required (called a group of pictures, GOP).

I don't know how true that is. Most of the Chinese DVD players run some
sort of Linux with an mplayer/vlc/xine derived playing engine. AFAIK they
all have a mechanism in place to load a new set of firmware into flash,
although details of the exact mechanism and how to package your own 
version are obscure. 

So far no one seems to have bothered to produce the equivalent of DD-WRT
or Tomato, etc (Linksys WRT54G-L router) Linux distributions for 
custom loading, nor have customization toolkits appeared for them.


>If by professional production you mean disc encoding, then sure.  

Yes.

>I only point this out to say that professional production can be really
>gross, and obviously top quality isn't always required.

Yes. As I watch Conan O'brien hoping to see a funny joke, which is
converted to 4:3 PAL and then subtitiled before being shown here, it's
very obvious. I wanted to see something that had not been shown here yet
so I downloaded a 16:9 off the air "recording" and watched the show.

The quality of the video was still good, and except for Shatner's poetry
reading (who BTW, is Jewish), it was still as Leno used to say "Yom Kipur
when all the Jewish writers are off". :-( 

>> Once the data is encoded, compression is applied. MPEG-1 was designed
>
>Since several of the steps along the way to this point are throwing away
>data, I would argue that data is already being compressed.  

You could, and I probably would agree with you in principal, but I wanted
to diferentiate between encoding and compression. 

>AAC was actually introduced in MPEG2 Part 7.

Ok, wouldn't that make it too late for the MPEG2 used in DVD's or was it
considered just too complicated for the time?

>Both MPEG2 and MPEG4 have been extended to carry numerous audio types
>other than just MP3 or AAC.  Also extensively used are AC3, AC3+, DTS,
>and Dolby E.

As long as a DVD has a "regular" audio track too, then the disk would
be compatible with older players, assuming anyone has them. Mine last 
3-6 months, depending upon the abuse my kids give them and how rarely they
get the dust blown off.

Our living room DVD player is a computer running Mythtv, which used to go
through DVD drives every 6 months until I started putting the heavily used
stuff as MP4 files on the hard drive. Before anyone goes and says anything,
I'm not in the US, it's legal here.

Geoff.

-- 
Geoffrey S. Mendelson, Jerusalem, Israel gsm at mendelson.com  N3OWJ/4X1GM