Transcoding vs Reencoding - Is there a threshhold?

[walkistalki]

Hi,

as reencoding a DVD implies some quality loss as well, I'm wondering if for very low compression ratios transcoding would give better results then reencoding and if there is some way to find the break even point?

Any ideas?

[E-Male]

i think it also depends on teh source material
a very clean source (cg at best) can be transcoded, also at low percentage/bitrate, while grainy sources are tricky no matter what you do

[lrosado]

You have it backwards. For low compression ratios you should re-encode. Transcoding is better when you're not compressing so much, depending on the movie of coarse. You should always use you're judgement on the results of transcoding. If it's bad and not acceptable then re-encoding the movie will yield better results. Just remember that the lower compression levels you use, raises the chances that you wont get an equal, in quality, copy.

[walkistalki]

i might have used the wrong terminology.

i'm talking in cases when you reduce the size only by a couple of %.

regards,

[maa]

You have it backwards. For low compression ratios you should re-encode. No - otherway around !:)!

Compression is squashing:
High compression is a LOT of squashing.
Low compression is only a little bit of squashing.

maa
____________________________________________________________
"He who doesn't say what he means doesn't mean what he says"

[Kedirekin]

There is no right or wrong. It's all a matter of semantics.

In DVDShrink, a compression ratio of 97% is very light compression. It means the end result will be 97% of the size of the original.

In another situation (where DVDShrink isn't involved), a compression ratio of 97% might be interpreted as very, very heavy compression.

Incidentally, I just wanted to mention the third option
- transcode
- re-encode
- split to two disks

[MackemX]

maa simplifies it and Kedirekin shows how it's the software's that may confuse other people :). Most at 97% mean 100%/97% or a compression ratio of 1.0309:1. It's a 3% reduction if you look at it the other way

if you compress something by 10% then it will be 90% of it's original size. If you reduce something to 10% then it's reduced by 90%. It's all about the words used as I could just say 'a compression ratio of 10%' and people may not have a clue what I mean as it can be taken either way ;)

walkistalki was right from what I read as a low compression ratio is 1.0309:1 (97%) and 10:1 (10%) is a high compression ratio :)

a 4th option could be wait for dual layer :D. Come on people, what's the big deal in having a slightly inferior backup for a few months? Seeing as DVD blanks are pennies now, back it up now and then you can back it up again when dual's are cheaper seeing as you own the original ;)

[maa]

1.0309:1 (97%) and 10:1 (10%)

Working with audio compressors the defifnition is pretty clear,
10:1 means any 10 going in get reduced to 1 coming out.

I think using "percentage" and "ratio" in one sentance is causing the confusion - its like having colored colors !;)!

[brynolf]

I just recently made a main movie only cce encoding of a big movie (2:50 hours) and for comparison I tried to make a shrink copy as well. The movie was compressed down to 68 % of its original size and I actually thought there was no big difference at all. I actually think that shrink did a slightly better job, there were less noticable flaws.

This is of course only my opinion, but I think that cce is actually pretty overrated...

[Kedirekin]

I'm of the opinion that encoding versus transcoding looks something like this:


|ººººº
|·····º·º·º·º·º·º·º·
q | º·º·º·º···
| ºº ···
u | º ··
|-----------------------------º----·----------- Minimum Acceptable
a | º ·
| º ·
l | º · · CCE
| º · º DVDShrink
i | º ·
| º ·
t | º ·
| º ·
y | º ·
| º ·
| º ·
|----------------------------------------------
c o m p r e s s i o n


For very light compression, DVDShrink (and transcoders in general) produce slightly better quality - closer to the original source. For a broad range beyond that, Shrink and CCE produce roughly equal quality (different but comparable). In my opinion there is only a small slice where CCE produces acceptable quality where Shrink does not.

Unfortunately, as has already been stated, where the lines lie depends a lot on the movie and on the person watching it. For what it's worth, where the lines lie doesn't factor into my decision on how to process the movie. I value my time highly, and I'd rather spend an extra $2 and split the movie to two disks then spend the extra time re-encoding and re-authoring.