Decompression instead of compression

16th July 2005, 17:02

Just to try I gave DVD-rebuilder a DVD to proces that was about 3.38 GB.

Just ignoring the warning that it compression wasn't necessary I did proces the disc with CCE SP 2.66 (3 pas).

The output was sized at 4.35 GB, so 33% more !!

I got higher bitrates and with bitviewer lower q-factor (compression).

The main question here, is it possible that the picture quality improves by doing this ??

Watching it on my 80 cm pixel-plus widescreen, did believe me improvements to be seen, but that's maybe totally subjective.

Anybody ??

jon.schaffer · 16th July 2005, 17:52

It's impossible: MPEG compression loses details. They are permanently lost. You cannot 're-create' them by a decompression step (which is rather a re-compression step)...

Rockas · 16th July 2005, 18:06

Quote:

Originally Posted by apfraats

Just to try I gave DVD-rebuilder a DVD to proces that was about 3.38 GB.

Just ignoring the warning that it compression wasn't necessary I did proces the disc with CCE SP 2.66 (3 pas).

The output was sized at 4.35 GB, so 33% more !!

I got higher bitrates and with bitviewer lower q-factor (compression).

The main question here, is it possible that the picture quality improves by doing this ??

Watching it on my 80 cm pixel-plus widescreen, did believe me improvements to be seen, but that's maybe totally subjective.

Anybody ??

See it as a photocopy... you can make the copy bigger but not better

16th July 2005, 18:22

I imagine that the output could even be of lower quality as the re-compression process would not act on the picture in the same exact way, therefore you could have both the loss from the original compression process and some additional loss from your re-compression.

steptoe · 17th July 2005, 00:31

All thats happening is the CCE is resizing the source video to match the size set in the config, exactly the same as fitting an oversize DVD, but this time its an undersize DVD

Thats why the bitrates are higher, to take into account all of the space. It will try to fill the DVD, but if you have a short film, it will pass the maximum limits to create a DVD, and you may end up with same space left on the destination DVD

Don't worry about it, its impossible to iimprove the source, unless you start using AVISynth and various filters which all take time if they are complex filters

the old saying :

crap in = crap out

jdobbs · 18th July 2005, 01:59

It depends on a lot of things... sometimes recompression can actually make a picture look better, not because of the higher bitrate, but because MPEG compression can sometimes soften the picture a little. It isn't actually "better" -- but a little bit of a filtering effect can sometimes be a good thing, especially on noisy sources.

16th July 2005, 17:02	#1 \| Link
apfraats Guest Posts: n/a	Decompression instead of compression Just to try I gave DVD-rebuilder a DVD to proces that was about 3.38 GB. Just ignoring the warning that it compression wasn't necessary I did proces the disc with CCE SP 2.66 (3 pas). The output was sized at 4.35 GB, so 33% more !! I got higher bitrates and with bitviewer lower q-factor (compression). The main question here, is it possible that the picture quality improves by doing this ?? Watching it on my 80 cm pixel-plus widescreen, did believe me improvements to be seen, but that's maybe totally subjective. Anybody ??

16th July 2005, 17:52	#2 \| Link
jon.schaffer Eternally Junior Member Join Date: Apr 2004 Location: France Posts: 230	It's impossible: MPEG compression loses details. They are permanently lost. You cannot 're-create' them by a decompression step (which is rather a re-compression step)... __________________ "Methinks it is like a weasel" (Hamlet in Hamlet, by Shakespeare)

18th July 2005, 01:59	#6 \| Link
jdobbs Moderator Join Date: Oct 2001 Posts: 20,976	It depends on a lot of things... sometimes recompression can actually make a picture look better, not because of the higher bitrate, but because MPEG compression can sometimes soften the picture a little. It isn't actually "better" -- but a little bit of a filtering effect can sometimes be a good thing, especially on noisy sources. __________________ Help with development of new apps: Donations. Website: www.jdobbs.net

16th July 2005, 18:22	#4 \| Link
zacoz Guest Posts: n/a	I imagine that the output could even be of lower quality as the re-compression process would not act on the picture in the same exact way, therefore you could have both the loss from the original compression process and some additional loss from your re-compression.

17th July 2005, 00:31	#5 \| Link
steptoe Registered User Join Date: Mar 2003 Location: UK Posts: 360	All thats happening is the CCE is resizing the source video to match the size set in the config, exactly the same as fitting an oversize DVD, but this time its an undersize DVD Thats why the bitrates are higher, to take into account all of the space. It will try to fill the DVD, but if you have a short film, it will pass the maximum limits to create a DVD, and you may end up with same space left on the destination DVD Don't worry about it, its impossible to iimprove the source, unless you start using AVISynth and various filters which all take time if they are complex filters the old saying : crap in = crap out