compression help

2005-01-18 04:39:21 am

Ben Goldberg

I'm using divx to compress some files, and it works great, but there's some stuff that's bad. The one that I need to fix is, when you use divx on a video file that has numbers on the screen, the numbers become very hard to read. Does anyone know how to preserve more detail or anything like that?

Thread title:

Radix

2005-01-18 04:44:07 am

I'm addicted to games

Are you doing a 1-pass or a 2-pass?

Cygnus

2005-01-18 04:47:11 am

Ben Goldberg

2 pass.

Radix

2005-01-18 04:51:50 am

I'm addicted to games

Well if the numbers are still blury the only thing I can suggest is to extract the sections of video that have numbers you want to be clear and encode them at a higher bitrate, whatever is necessary to make them clear. Then encode the other fragments at the normal bitrate, and append all the final files together and save it with 'direct stream copy'.

Cygnus

2005-01-18 04:57:10 am

Ben Goldberg

Heh, well, the whole section has numbers at the top, but they're readable. But still, at one point, there's a five at the top and the whole top line of the number 5 has magically vanished. You can still see it's a 5, but it's preety bad. I'll try raising the bitrate of the whole video and see if the file is too big or not.

Cygnus

2005-01-18 05:08:10 am

Ben Goldberg

I raised the bitrate way up and it didn't fix the problem, so I'll just have to live with it I guess.

Andy_Olivera

2005-01-19 05:10:52 am

Try turning off "Psychovisual Enhancements" and/or "Source Pre-processing".

Trevor

2005-01-19 02:19:07 pm

if you're capturing below 320x240 (just checking - sometimes it's the obvious stuff...) then that'd easily explain it. try messing with the brightness/contrast to get the text to stand out a little more without compromising overall picture quality that much.

also, you could try capturing at a high res (640x480) and then resizing to 320x240 using a high quality resize filter like Lanczos. it'd produce a better looking 320x240 movie anyhow because you'd be making something interpolated from more data originally than just capturing straight to 320x240.

you could also just try a sharpening filter - there ought to be ones on virtualdub and avisynth.

Radix

Edit history:

Radix: 2005-01-19 02:43:54 pm

2005-01-19 02:43:10 pm

I'm addicted to games

Quote:

also, you could try capturing at a high res (640x480) and then resizing to 320x240 using a high quality resize filter like Lanczos. it'd produce a better looking 320x240 movie anyhow because you'd be making something interpolated from more data originally than just capturing straight to 320x240.

No that's a very bad idea. If you are able to capture at 640x480 you should do so, but then you have to deinterlace the frames to end up with 60fps at 240 lines. You can then resize it back up to 480 lines if you want, but there's no point for older games. If you just resize 480 down to 320 you'll end up with a blurry mess.

Trevor

2005-01-19 05:17:11 pm

haha, yeah you're right, i totally forgot... but you can still safely capture 640x240 and use the horizontal information if the card supports custom resolutions.

Andy_Olivera

2005-01-19 10:31:21 pm

Quote:

you can still safely capture 640x240 and use the horizontal information if the card supports custom resolutions.

You're only capturing one field that way. It's better to capture at 640x480, deinterlace, then resize.

If your card can capture both fields, when you deinterlace, either use Nate's 60fps method(which I personally hate, but that's another story), or use the "Blend fields together" option(not one of the "Duplicate Field" or "Discard Field" options; those throw away half the movement).

When downsizing, VirtualDub's "2:1 reduction (high quality)" filter is the best option. If you don't believe me, add the filter, set the output monitor(right side) to X2 and compare. It preserves a surprising amount of detail.