High vs. Low Resolution

[fredheadgt]

I am new to Divx 4 encoding, so I still have a lot to learn. I have a newby question for you all, and I've searched the forums but have not been able to find a definitive answer...

In all the Gknot Divx 4 guides, they tell you that to increase your video quality, you should DECREASE your resolution. As you increase the resolution with the slider, the percentage for the compressibility test goes down, which the guide says leads to inferior image quality. In a way, this makes sense because the larger the picture, the more space has to be filled up at the given bitrate. But here is my question...If you want to watch a divx movie in fullscreen, wouldn't a higher resolution be better? If you take a jpeg image, for example, and stretch it, the quality drops quite a bit. It seems to me that the less stretching had to be done, the less the drop in quality. Any input would be greatly appreciated.

[dragoman]

Hi,

First, you are correct in stating that a smaller resolution will allow more bits to be concentrated in the picture, thereby increasing the image "quality" (a highly subjective judgement best made by each person for themselves).

However, what you seem to think is that when you play a movie at fullscreen on your computer, you are changing the resolution. You aren't.

The source resolution remains the same. A movie encoded at 640x272 will remain that way. The only thing playing at fullscreen does is put the movie through a "resize filter", one that is built into any player.

Yes, you are correct that some movies when played at full-screen look horrible because of their low quality, whereas playing them at less-than-fullscreen makes them look better.

But this has more to do with the quality of the movie rather than the resolution. A movie encoded at at high bitrate and a low resolution will still look quite good when played at full screen.

Yes, you are correct in saying that a movie encoded at a higher resolution will not look as bad as a movie encoded at a lower one (when played at full-screen), but that is only if hte image quality of the movie (i.e. for DivX, the bitrate) is the same.

In reality, resolution is a personal choice. I personally encode at 640x or higher. Whatever you think looks good is what you should go with.

dragoman

[movmasty]

>the less stretching had to be done, the less the drop in quality

also the less the cpu usage.
but stretching should be 1:2 to give best results.

that is taken into account,a better looking small res can look worst when stretched, but if the movie at large res gets too compressed, it is ruined

[fredheadgt]

Thank you for your quick answers. I think I understand the whole resolution thing now. Many thanks

[BluDChyLD]

i've always followed gknot compressibility test myself. If it goes below 384 res without being over 60% quality i'll change to 2cd instead. My friend encodes at 352x192 no matter what! They don't look too pretty...
BluDChyLD

[rmatei]

"Stretching" (overlay) does have something of an influence, but all in all, it's much more important to worry about getting a good "unstretched" picture. With a given bitrate, the idea is:

- Lower resolution means the same amount of bitrate is spent on less pixels. Therefore, the lower the resolution, the "cleaner" a video will look, because there will be less macroblocking and compression artifacts. The downside is that it also looks blurrier.

- Higher resolution means the same amount of bitrate is spent on more pixels. Higher resolution rips look crisper, but they have more artifacts and macroblocking.

Where to rip, between the two above cases, depends on your tastes. The first pass % in GK is an excellent indicator. See what % looks good for you and try aiming for that. 60% is very clean but a bit hard to acheive on 1 cd rips. I find that 50% is more appropriate for me (more towards sharp/blocky), but like I said, it's personal taste.

[BluDChyLD]

ah right I see now, I thought that you should aim for 100% if the res it still high as that gives the best quality. I did that with one or two films, you do get a smooth picture but its pretty blocky...