Several questions about GKnot

[snowbeach]

Several questions about GKnot


1. What means Aspect Error and what does it mean in combination with the Aspect Ratio?

2. What is Smart Crop All doing to get a perfect Aspect Error of 0%?

3. Sometimes changes the Aspect Ratio using Smart Crop All to get an Aspect Error of 0%!
Why?

4. Is it better to use smaller Output Resolution (width x height) for a better
Bits/(Pixel*Frame) result? What about the video quality watching the encoded movie in
fullscreen afterwards?

5. What is meant with the Interleaving & AVI-Overhead section at the Bitrate tab?
(esp. Calculate Frame-Overhead?)

6. AVS script...
# RESIZING
BicubicResize(640,352,0,0.5)
What does (...,...,0,0.5) mean?

7. How does Re-Calculate Bitrate if needed function?

Thanks in advance! ;)

[hakko504]

(<Final Aspect Ratio>/<Desired Aspect Ratio> - 1) * 100
It's the difference between the aspectratio you have and the aspect ratio you want. This number should be less than 2~3% or you will notice distortion when viewing the final film.
It crops the original picture. (D'oh :rolleyes: ) That means it calculates exactly how much that needs to be removed from all four sides to get the perfect aspect ratio.
I'm not sure but I think that happens when it can't find a perfect aspect ratio with the settings you want, and has to change the final resolution to get a better match.
Smaller resolution: less details, needs less bits.
Larger resolution: more details, needs more bits.
A larger resolution will look better most of the time, but unless you have enough bits to encode it it is much more common to get blocking when you use large resolutions. The compression test is a good way of finding the best compromise between details and sharpness given a number of MB.
Interleaving states how often the AVI will switch between audio and video. Every switch uses a fixed number of bits and thus using lower values for interleaving will cost a few MB. The lower this value is though the less likely you are to have audio-video desynch, i.e. the computer will keep audio and video together so you don't see a person's lips move frst and then hear the sound.
Bicubicresizing can be implemented in a number of ways, and the last parameters defines a sharpness fo the resize. 0,0.5 is a quite neutral setting that will not produce ringing and also won't soften very much. A setting of 1/3,1/3 will soften the video, increasing the compressability. Using 0,0.6 or higher will sharpen the video but can cause ringing.
<Final size[in MB]>*<framerate>/<number of actually encoded frames>
Ringing: Let's say you have a white background with 1 black pixel. When you resize this picture with a sharp setting you will get grey rings around the black pixel. That is called ringing.

[snowbeach]

Thank you very much for the fast answer! :)

[theReal]

One addition to your first question:

Better use a resolution with some small aspect error (up to 3%) than use an "atypical" resolution. You lose compressibility and compatibility when your resolution is not divisible by at least 8.

I'm pretty sure that nobody can see an aspect error of 2% - at least I can't.

[snowbeach]

A movie that has an aspect ratio (e.g.) of 2,35:1 is resized by GKnot to 640x256! :confused: Should not it be resized to 640x272?

FYI. I never use Auto Crop, because it is not working very well - it leaves sometimes black borders - so I crop manually. Then I use Smart Crop All or Smart Crop Left/Right! I often use Smart Crop Left/Right to get the desired resolution - in this case 2,35:1 and the related 640x272! I believe that I have to use the "correct" resolution! And I always leave the ITU standard checked, but I have the same "problem" when I uncheck it!