I never mentioned having anything
extraordinary in this setup!
Im now attributed sky digital I don't even
have!
Those are all things ken has thrown
in.
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.
All I said is that once I have the signal
inside the PC compression is lossless.
I don't pretend to defy the laws of a/d d/a
conversion. I took that as read.
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.
Again I'll attempt to clarify the value of
lossless compression.
Mpeg is based on the same concept as
jpeg.
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.
Thats my point.
Once it reaches where I can control it, I
don't immediately add noise by capturing in a compressed
format.
I edit, crop, and titles, effects all
losslessly. Please, this is common practice!
The Last stage is mpeg2 compression.
Sometimes I keep the lossless compressed material as well, which is big
but thats life.
Now, surely this is clear now
guys.
Jason
----- Original Message -----
Sent: Tuesday, May 28, 2002 12:02
PM
Subject: RE: [ukha_d] Lossless
Compression Help!
To hopefully clear things up
to quote you 'OK, the
PC capture of whatever feed is
lossless...'
this is not the
case as the PC capture involves a Analogue to Digital conversion, the
only way around this is to use Sky + as Ken
said.
LNB to Digibox
- Digital Connection
Digibox to RBG
or S-Vid out put invloves a D/A Conversion
so we are now
in the anlogue domain and now you have to do another A/D conversion to
get the feed into SS, this will be done by the TV capture
card.
all of these
A/D conversions are NOT good.
What you do
with the captured file may well, be lossless, but you have already
degraded the signal by the A/D
conversion.
Regards
Ben
Oh Jesus!
I keep putting things as simply as I can
and still people jump down my throat.
I've got lots of books as well. No really
I have.
If I send you a zipped file and you unzip
it. Do you get the same file? Or is it different?
THAT IS LOSSLESS COMPRESSION. Go look up
huffyuv. Its
here...http://math.berkeley.edu/~benrg/huffyuv.html
I'm not sure if the you will
*apologise* for spouting utter nonsense about
compression.
Now that fact is dealt
with...
The point of using lossless is not to
produce more artifacts. I understand that the digital feed is already
compressed. I just don't want to add more noise until the
end.
People work in lossless and then compress
down at the last stage.
I suggest you try reading some of your
books sometime :)
Jason
----- Original Message -----
Sent: Tuesday, May 28, 2002
11:37 AM
Subject: RE: [ukha_d] Lossless
Compression
The point
being Jason that any form of compression and manipulation of the
file *will* introduce
loss and affect the quality of the image. If your digibox un-compresses the stream then there is a
loss in that, then you are re-compressing it for storage (loss
again), then decompressing it to view (still more loss)…NOT
lossless!
Any form of
capture, compression or manipulation will introduce certain
artefacts into the picture whether you notice them or not, although
there is many a software “trick” to minimise the impact of such
manipulation. If you like I can loan you a couple of good books that
explain this but it isn’t exactly light reading
material.
K.
-----Original
Message-----
From:
Jason Lee [mailto:jasonjlee@xxxxxxx]
Sent: 28 May 2002
11:27
To:
ukha_d@xxxxxxxSubject: Re: [ukha_d] Lossless
Compression
OK, the PC capture of
whatever feed is lossless...
Like taking a file and
using zip to compress it. The file when uncompressed is exactly the
same as the source. Lossless
As opposed to using
jpeg/mpeg/mjpeg which uses tricks to compress images down. When the
image is uncompressed it is not identical to the source. Not
lossless.
Look at matroxusers web
site vcdhelper, any big video editors website for details as to why
this is a good idea...
I don't only capture
>from
deck.
----- Original Message
-----
Sent: Tuesday, May 28, 2002
11:19 AM
Subject: [ukha_d] Lossless
Compression
Jason,
This is really a question for
you...
How are you
achieving lossless compression with
SS?
I was thinking
about this last night and the only way I can see of
doing
this is to take
a feed into a SAT card in the PC direct from the LNB
to
catch the digital
stream before it is decoded thus achieving a
lossless
compressed
file. The problem with that is that there is no CAM
available
for Sky
Digital to enable this to be done with a SAT card or
TV.
AFAIK the only
way to do this, or more accurately, the only system
that
can do this, is
Sky+ as it actually records the stream directly
and
plays back as it
would be presented straight off the
air.
If you are
running it through the STB and then transferring that
signal
to your SS
machine then that is not lossless, you are in fact,
doing
what any PVR or
VHS machine would do.
K.
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