-----Original
Message-----
From: Jason
Lee
[mailto:jasonjlee@xxxxxxx]
Sent: 28
May
2002
11:54
To: ukha_d@xxxxxxxSubject: Re: [ukha_d] Lossless
Compression Help!
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 :)
----- 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 tv, I
capture from dv and my s-vhs 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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