resizing xvid problems

[Snowcrystal]

Hi,

I have a bunch xvid files which are 848x480. Now my divx dvd player only plays up to 720x576 for 50hz or 720x480 60hz. Now I've tried to resize it using virtualdubmod with the resize filter. I tried 720x480 and also 702x480, using the same bitrate as the original file and using xvid codec. But the result is pixelated and the image is somehow stretched. I think 480 should be another number but which number is the correct one?
I've resized a xvid file before with the same method and I didn't have those problems.
Anyone know how to fix this?

thank you very much

[Bjs]

Post a snapshot of what it is you are seeing ...

[markc32]

well it suggests a resolution on the y-axis of 410.

It is using 1.76 to 1 widescreen.

So you need to ensure you keep aspect ratio when re-encoding. You will have to re-encode anyway as it is a total non-standard resolution! you could use a simple re-encoder for this but if you want the best - your problem is not so much aspect ratio as to black bar banding out of place.

Use an application that keeps things uniform!

[Snowcrystal]

I've calculated the aspect ratio so it's 1:1 but the image still isn't fluid as you can see below.
So how can I fix this ?

original


resized

[mats.hogberg]

What resize filter? No matter, reencoding an XviD to XviD won't look that great.

/Mats

[Snowcrystal]

The one that comes along with virtualdubmod.
I know the quality will get worser but I've resized a xvid video before and the image wasn't like this. This time the image looks distorted.

[mats.hogberg]

There are different kinds of resize filters. Bilinear, bicubic, Lanczos? I'd suggest Lanczos, if that's not what you use already.

/Mats

[Bjs]

As this video size is unique to this clip ...

848 - 720 = 128
480 - 128 = 352

Keep's original scale ... then use expand frame and letter box is 720x480 ... add's black bar's top and bottom .

Should be right ... it's where I would start first .

--------------------

To get it close as possible you will need to perform a two pass encoding .

In the middle , down the bottom of vdubs gui are two black arrow key's .

Move forward in video and locate the first frame of test clip , hit that left button (black arrow key)
Now move forward till you have enough for test clip , and hit the right button .

This lock's test clip .

Now setup video filter requirement's ...

Now head to video compression and choose xvid .

From here , it's a guess as not all video clip's are the same ... different light level's and such .

Use the original video bitrate as lowest ... and for the higher value , increase it by 15% .
Some suggest it is better this way ... though I dont .

Save as avi , then playback this file and see how it went .

You may need to do this a few time's before you get those video filter's and bitrate value's more in tune with the resizing and type of video ...

[jagabo]

On VirtualDub's resizing filter use the pulldown below the frame dimensions to set the filtering mode to Lanczos3. That will take care of the jaggy edges in the sample you posted. 720x400 or thereabouts might play OK, but many players will be even happier with 640x360.

For Xvid encoding, if you don't care about the exact size, use Single Pass, Constant Quantizer mode (constant quality). You pick the quality you want and the file comes out as small as possible to give that quality. If you want the output to look almost exactly like the input, even when viewing enlarged still frames, use a quantizer value of 2 (some players may have problems with this as the bitrate may get too high, especially if the frame is large -- one reason I recommend 640x360 rather than 720x400). A quantizer of 3 will look nearly identical to the source at normal playback speed. As you go to higher quantizer values the picture gets worse and the file size gets smaller.

The only time you want to use a 2-pass encode (where you know the size of the output but not the quality) is when you need maximum quality for a FIXED file size. Like when putting a 90 minute movie on a 700 MB CD.