What exactly does 'Deep Analysis' do??

[archaeo]

I have read that it will increase the quality of your image, but what exactly is going on? All I see is that it usually takes about 40 min to analyze, and it pegs one of my CPU's at 100% the whole time (I run dual 1 Ghz PIII's). Follow that with another 30 minutes of encoding (CPU=100%) and it is an intensive process. Are you seeing similar times? Any danger to the CPU for a prolonged period at this rate? Just wondering.

[adam]

When asked what the function does...

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

[archaeo]

Excellent explanation!
Can you lead me to the post where this quote originally came from?

Understanding the process helps me to understand how each tool can or cannot be used. I can see why it is best to run it when the compression ratio drops into the lower numbers. For that matter, if I have the time, I could always run it.

I notice that you are a moderator, and I thank you for taking the time to answer my question. May I add that this forum has been indispensable to me in learning DVD recording. Thanks!

[jimmalenko]

It does not improve quality - it can't. It prevents quality drop by working out where it can skimp on bitrate in order to lower the size, that's all.

[archaeo]

It does not improve quality - it can't. It prevents quality drop

yes, I didn't say that right. I understand that it can't improve upon the original.

[jwedge]

don't to sound stupid but are we talking about a feature in DVD Shrink? I looked into preferences and didn't find anything about 'deep analysis'

[jimmalenko]

Yes we are dude.

[adam]

I found the reference to this quote in this thread.
http://forum.doom9.org/showthread.php?s=&threadid=63587

You can read it in the last post there. My guess is that the actual post came on DVDShrink's official forum, but I don't know for sure.

[Thunder In Paradise]

Basically it stops the quality of the video from getting junky at higher compression ratio's, or any compression ratio for that matter by analyzing every frame in the movie, instead of analyzing blocks of frames at a time. This is why it takes longer then normal. With my P4 2.53Ghz Oc'd to 2.87Ghz, this process takes about 23-26min.

[archaeo]

With my P4 2.53Ghz Oc'd to 2.87Ghz, this process takes about 23-26min.

Are you also noticing your P4 running at 100% during the process?

[mrbass]

that quote IIRC came from a closed beta testing forum which was never opened to the public...thus I snagged it outta there before it was deleted. dvdshrink said it was ok to quote that paticular snippet.

[Thunder In Paradise]

Well duh Archaeo.