Improving the encode with the KDVD template?
 

Hi All,

This message is meant primarily for Kwag, but also for anyone else who can answer.

I'm looking for ways to improve on Kwags most excellent KDVD template.

So basically, what I'm wondering is, would I improve quality if I switch to 2-Pass VBR. If so, what Min/Max/Ave bitrates would you reccomend ?

Or, if it's better to stay with CQ, what kind of an improvement can I expect to see if I change the CQ setting to 70 or 75 instead of 65. I understand that this will affect file size.

Also, one last question. What effect would there be if the outputting aspect ratio is changed from 16:9 to 4:3 ?


Thanks 2 all

Is there anyone that can provide info to answer my questions ?!?!? :cry:

Read about CQ vs. VBR, and why CQ it is the best here 8)
http://tangentsoft.net/video/mpeg/enc-modes.html

kwag

OK,

I read the page at the link and think I understand CQ vs n-Pass VBR better now.

So still on this, will bringing the CQ above 65 dramatically improve the visual quality of an encode or is the file size gain just not worth it ?

And does changing the outputting aspect ratio from 16:9 to 4:3 where the source was 16:9 affect the file size or visual quality in any way ??

Thanks again .,... :?:

The best way to test the CQ it to make small clips at different CQ values, say in steps of 2. You do this on very low action or almost still movie scenes. You will notice that once you get below a point, the video will start to look unstable. I mean the still parts of a movie, for example a wall, will look like it has artefacts on it and there's a wavy efect. So if you start to increase just to the point where you can't see this effect, that's your minimum CQ value. Beyont that point, there's no more visual quality increase. Just file size. You don't have to worry about the high action parts, because that's where the MAX bit rate jumps in. So the quality will be constant, no matter it it's a low action or high action scene. The CQ works different, depending on the resolution. A CQ of 70 will look ok with the KVCD template at 352x480, but not at 352x240. At 352x240, you need a CQ of around 78 to look the same. At 704x480 the CQ of 50 looks just like CQ of 70 on the 352x480. So it's not a linear value.
As for 16:9 or 4:3, if your input is 4:3 full screen, the file size will be much larger than a 16:9 movie. There is more visible area for the encoder to work with. As for output aspect, you must encode at 4:3 for VCD's.

kwag

i tried play 704x480 but i changed CQ:80 is this the cause that it didnt play correctly on my daewoo 5800?

I don't think so. You're just raising the average bit rate by increasing the CQ. Also at 704x480, beyond around CQ=60, there's no more visual quality increase. Just file size increase.

kwag

Got another question for you Kwag.

Why is your GOP structure and funky matrix more efficient than what we've all come to accept as Mpeg1 or Mpeg2 standard ?

Ohh, and as to the output aspect, I was reffering to using the KDVD template where my source was 16x9. What I really wanted to know was, if my output aspect ratio is 4x3 are my horizontal bars consuming disk space ?

Thanks for all your help & info ....

The MoovyGuy 8O

The long GOP is what gives the high compression. The funky matrix is not mine. It was done in Germany by a fellow named Andreas at the dvd-svcd.de forums.
Black bars don't consume bit rate ( sort of ). In a full screen movie, you have pixels consuming the complete screen. So the file will be larger. That's why wide screen movies take less file space, because they have black bars, and the encoder has less pixels to deal with and compress. If you have a complete black screen, at least in a KVCD template, the bit rate would be theoretically 300Kbps, because that's the MIN value in the template. So really the answer to your queation is the larger the visible picture area, the larger the mpeg file. It's not really aspect related, but the amount of visible pixels .

kwag

Well I'll tell ya,

The intricacies of GOP structures and matrices are a bit beyond me, but I understand them enough to appreciate what the KDVD template can do for me and really appreciate them.

If it wasn't for them, having a DVD burner, considering current costs, would hardly be worth it.

Thanks again...