Pixalation at Scene change

[Marco33]

Capture seems to pixalate at scene changes and no where else. Not all the time.

Doesn't seem to matter if I capture VHS, LD or different bit rates.

Might be the card's software.

[Triffid]

Are you using an MPEG capture codec?

If so, try using Huffyuv or an MJPEG codec. Or use I only frames, or give it more bit rate to work with.


Hope this helps!

[Marco33]

I only frames. Which gop setting is that?

It captures direct to mpeg 2 at any bit rate.

Bit rate doesn't seem to matter.

[Syndrome]

I simply capture to uncompressed UYVY AVI.
yes its very large (2 hour movie is ~40gig) but you get the picture perfect DVD quality results, without any distortion, and always in-sync sound

but anyways thats just me
Syndrome

[Triffid]

I'm not sure what codec you are capturing with, so I can't say which (if any is available) setting would give you I frames only, but if you can adjust the GOP settings, set for 0 P frames and 0 B frames. The reason this should help is that part of MPEG comprssion is to predict motion from the previous (and next) frames and reuse parts of the picture. At scene change it is very unlikely that you will get much reuse, so the codec has to rely on quantization of the current frame for it's compression, and that's where the pixelation comes in (especially at lower bitrates).

Personally, unless you only have a very small capture disk, or you are trying to bypass the whole 'after-capture conversion' thing (to save time), I would go to a different compression codec as suggested. The two disadvantages of using raw YUVU or RGB capture (over huffyuv or MJPEG) would be size of (fast) diskspace required, and increased disk bandwidth requirements but it certainly reduces the processor load, and introduces no additional distortions....so it depends on your situation. I use huffyuv for home video captures (approx 30 minutes) and MJPEG if I am capturing whole movies to back up my VHS collection

(I'm in the middle of Empire Strikes Back at the moment, 17Gbytes MJPEG capture, and between field order swaps of the original tape, and tweeking of the the encoding settings to get good quality on one DVD I have had the PC working full time for the last 4 days. Hopefully it will be ready tomorrow.)

[Marco33]

The program that came with the card captures straight to mpeg2.

I don't see a difference at differnet bit rates.

There is no compression except for the bit rate settings.

set for 0 P frames and 0 B frames

I see GOP & sub GOP. Is that what you are refering to?

By the way I just did a LD conversion of the trilogy. If you have any questions feel free to ask.

[Triffid]

In reference to I frame only capture:

Still without knowing what you are looking at: if there are GOP settings (that you can change), they will probably tell you how many I, P and B frames to have withing each GOP. eg:

IBBPBBPBBPBBPBB (1 I frame, 4 P frames per I frame, 2 B frames pre P frame etc). It might Say I=1, P=4, B=2 or something like that (the details are not important.

To get I only capture ,what you want a GOP to look like is 'I'. (ie 1 I frame pre GOP, 0 P frames, 0 B frames). It is quite possible that you can't do this though, but I'm sure it would help, if you can.

What sort of capture card is it, and is this software only compression, or is there hardware support?
Maybe there are other solutions to your problems if there is more information.

[Marco33]

It's a MSI TV@nywhere capture card.

I don't know where the compression is done.


It's set at the software setting so... I would say it's software.

I don't think there is compression, just bit rate setting.

Hmm, if I could post a picture here.

Never tried that.

[Triffid]

OK, here's my guess:

reduce the GOP and Sub-GOP parameters to 0.

It looks to me like they are the ratios of P and B frames respectively.

One word of warning: your capture file will be significanlty larger and the required disk bandwidth will be higher (having said that, I doubt it would trouble any reasonably modern system)

BTW: the MPEG stuff IS the compression. To use any other compression codec, you would need to be able to change to some other driver (maybe there is a selction for this somewhere in your capture card/program setup, eg 'Change capture plugin' - select a non-MPEG one)

[Marco33]

I will try that.

I have a setting to change the driver. That's what it looks like to me.

My video card captures also. I think the other driver is for that one.

[Marco33]

It woun't let me change the GOP & Sub GOP to zero. It said a number between 1 & 15 would have to be chosen.

So I chose 1 for both.

The output mpeg2 file hangs up Ulead even tho it plays fine on the computer.

If you need me I'll be @ square 1.

[Marco33]

Distance between " I " frames, I tried 6

Distance between " I/P " frames, I tried 3


Still pixalation.


Looking to try 15 & 5

[Marco33]

15 & 5 looks good, plenty of scene changes.