Perform "Deep Analysis" - DVD Shrink

[PoPPeR]

Has anyone actually tested and noticed any differences when having this option on versus off? It doubles the time it takes to analyze the DVD before burning. What exactly does it do? Is there an optimal time to use this, ie. when you only have to compress down to 90% versus 60-70?

 

[mrbass]

My advice...do it each and everytime unless your 95% or above.

This is an excellent quote from dvdshrink himself describing how deep analysis improves video transcoding within dvdshrink.

Someone asked him the following:
Is the prime function of 'Deep Analysis' to enable the program to arrive at the target size without doing some last minute, panic-stricken squeezing, or does it improve video quality?


quote:
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Both! It is dual-purpose. I'll try to explain in english, not math:

Suppose I want to achieve 50% video compression. The easiest way to do this, is take each picture, and squeeze it to half of it's original size.

The problem is, that not every data in a picture can be compressed. An encoded picture consists of both motion vector data and DCT coefficient data. It doesn't really matter what they are. The important thing is, DVD Shrink can only compress the DCT data.

It so happens that the amount of space devoted to motion vectors and the amount devoted to DCT data is different in each picture.

Suppose one picture consists of a 50-50 proportion of motion vectors to DCT data. To compress this picture to 50% of it's original size, you'd have to remove all the DCT data! Needless to say, the result would look awful.

Suppose another picture consists of 25-75 proportion of motion vectors to DCT data. To get 50% compression, you'd only have to remove 2/3 of the DCT data (still rather a lot, but hell, DVD Shrink sucks at 50% compression).

It would have been better to know in advance, that the first picture could not be compressed much, and the second picture could be compressed more. This way you could spread the compression evenly between the two pictures.

This is exactly the function of deep analysis, except on a bigger scale: it calculates the best distribution of compression over the entire 200,000 pictures of a movie. --dvdshrink

 

[BTGMan]

I also have dvd shrink which i got 2 days ago and i don't know how it works so can you help. thanks

 

[PoPPeR]

well there are some excellent tutorials out there, such as mrbass's website (www.mrbass.org). Without any specifics it's kinda hard to help you