Re: Lossless Compression Help!

["Jason Lee" <jasonjlee@xxxxxxx>]

----- Original Message -----
From: "Kenneth Watt" <kennwatt@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, May 28, 2002 12:45 PM
Subject: RE: [ukha_d] Lossless Compression Help!


> I never mentioned having anything extraordinary in this setup!
>
>> Nope.
>
> Im now attributed sky digital I don't even have!
>
>> So how did you remove the adverts from Sky One which you mentioned
in a
>> previous post?


>From NTL. Sky Digital and Sky One are not the same thing.


>> Those are all things ken has thrown in.
>
> Nope.

Yeah really. I don't have Sky Digital.

Show me one post where I say I've got Sky Digital? I'm on NTL.
I mention an NTL digibox in the tivo thread. Help!

> I understand that the feed into my pc is not straight from the back
of
> the camera the taking pictures.
> Thats obvious. I never stated any different.
>
> Nope. But the inference in achieving a lossless picture is that from
the
> point where it enters your home to the display is that the entire
> process causes no atrefacting or loss due to conversion.

I'm not talking about having a lossless picture, I'm talking about
using
lossless COMPRESSION in the pc.

> All I said is that once I have the signal inside the PC compression
is
> lossless.
>
> Nope, it's not. As I said any manipulation of the file will
introduce
> atrefacting or manipulation of what the software doing the job
considers
> to be superfluous just as a DVD player does or an STB does.

Right. This is outright wrong. PLEASE look at the thread I sent you.
Its like a gif as apposed to a jpeg. Please look it up.

>
> I don't pretend to defy the laws of a/d d/a conversion. I took that
as
> read.
>
> Nope, you can't, and this introduces noise to the picture and can
remove
> much of the detail.

Cool. We agree that signals going to a/d d/a conversion will lose some
quality. Fine!


> If you look back at my original post, I also capture from the s-vhs
deck
> which has no digital artifacts as its not digital.


> It will have artefacts, the question is are they noticeable enough
for
> you to see them? Admittedly D-VHS is far superior, superior even to
DVD
> for image quality and the allowable file size, therefore the less
> compression needed and the higher the image quality, S-VHS is only
one
> small step away from VHS, 525 line as opposed to 480 line
resolution
> IIRC.


>From one of my books! Dvd Demystified First edition

Page 210 Table 6.2

VHS Pal resolution
320x580

No statement of svhs res, but I seem to remember roughly 50% better.




> TiVo's capture is as good as S-VHS IMO on the higher quality
setting,
> perhaps slightly better, but can in now way, shape or form be
considered
> lossless.

OK. I'm sure it isn't. I think from what I've seen thats true.

> Again I'll attempt to clarify the value of lossless compression.
>
>> Hmmm, I still maintain that such a thing does not exist.

OK. Your wrong, but lets keep going with this.

>
> Mpeg is based on the same concept as jpeg.
>
>> Okay, we'll go with that.

Cool.

> If you take a jpeg and uncompress it and compress it again and
> uncompress it.
>
> You have more noise than the original. You even probably have more
noise
> than the 1st jpeg.
>
>> Yes, but the compression also removes certain elements of the
original
>> and this has been the whole basis of the argument over whether
analogue
>> or digital is better for audio for many a long year.

Jpeg/mpeg does not work in JUST that way. It produces mosquito
artifacts
around edges and lots of other things.
This is in the nature of the technique!




>
> Thats my point.
>
> Once it reaches where I can control it, I don't immediately add noise
by
> capturing in a compressed format.
>
> Yes, you do, whether you see it or not.

I don't add noise. Once its where I can get it digitally, I don't add
any
noise. really.

> I edit, crop, and titles, effects all losslessly. Please, this is
common
> practice!
>
>> To edit or crop *is* causing loss!

No it doesn't. Once its digital with lossless compression editing does
not
cause loss!


> The Last stage is mpeg2 compression. Sometimes I keep the lossless
> compressed material as well, which is big but thats life.



>> MPEG2 is a compression standard that cuts out certain elements in
order
>> to achieve a smaller file size, hence not a lossless standard.
Think on
>> it this way, is an MP3 encoded @ 96Kbs the same as an MP3 encoded
@
>> 128Kbs, short answer is no, it's not. Video is no different to
that, the
>> higher the bitrate, the better the quality and by recording to
MPEG2 you
>> are cutting the bitrate of the incoming transmission therefore
>> compressing and losing some of the original image.

Please read what I'm writing. I capture in huffyuv to a raid array. The
datarates are huge thats why the raid array is needed.
It is a lossless compression codec.
I edit in huffyuv. If I want it on dvd to give keep give to someone, I
compress to Lossy mpeg2.
I've never stated that mpeg2 wasn't lossy.


> Now, surely this is clear now guys.
>
>> As mud!

Oh now it must be surely. Please check the link I gave you and do some
research before posting anything else.





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