Re: Lossless Compression Help!

["Jason Lee" <jasonjlee@xxxxxxx>]

you cheeky b*****

;-)


----- Original Message ----- 
From: "Ben McCormack" <ben.mccormack@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, May 28, 2002 12:41 PM
Subject: RE: [ukha_d] Lossless Compression Help!


> Glad we sorted that one out, it still remains that TIVO is better
then
> ;-)
>  
> ben
> -----Original Message-----
> From: Jason Lee [mailto:jasonjlee@xxxxxxx] 
> Sent: 28 May 2002 12:37
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Lossless Compression Help!
> 
> 
> OK.
>  
> Once the data is where I can get it- its lossless.
>  
> I would have thought that was kinda obvious bar me being able to
hack
> the digibox.
>  
> If that was Kens point, then fine. But then he states lossless
> compression is impossible so I guess I'll leave it to the readers
again.
>  
> Just remember the next time you zip a file, your doing the
impossible!
>  
> Jason
>  
> ----- Original Message ----- 
> From: Ben  <mailto:ben.mccormack@xxxxxxx> McCormack 
> To: ukha_d@xxxxxxx 
> Sent: Tuesday, May 28, 2002 12:32 PM
> Subject: RE: [ukha_d] Lossless Compression Help!
> 
> I think that we have simply been confused by your post that stated
>  
> 'I am capturing to a raid array in a silencing enclosure.  I can
capture
> from my S-vhs deck or ntl digibox losslessly or with compression.'
>  
> All Ken was asking was how can you say that you can capture
losslessly
> when you have an A/D conversion in there? The A/D is going to
degrade
> the signal
>  
> I hope that this will be cleared up now
>  
> regards
>  
> ben
>  
> -----Original Message-----
> From: Jason Lee [mailto:jasonjlee@xxxxxxx] 
> Sent: 28 May 2002 12:22
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Lossless Compression Help!
> 
> 
> 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 ----- 
> From: Ben McCormack <mailto:ben.mccormack@xxxxxxx>  
> To: ukha_d@xxxxxxx 
> 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
> -----Original Message-----
> From: Jason Lee [mailto:jasonjlee@xxxxxxx] 
> Sent: 28 May 2002 11:54
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] Lossless Compression Help!
> 
> 
> 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 ----- 
> From: Kenneth Watt <mailto:kennwatt@xxxxxxx>  
> To: ukha_d@xxxxxxx 
> 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@xxxxxxx
> Subject: 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.
>  
> Jason
>  
>  
> ----- Original Message ----- 
> From: Kenneth Watt <mailto:kennwatt@xxxxxxx>  
> To: ukha_d@xxxxxxx 
> 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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