Capturing noise

[repo]

Hi,

Is there a way to capture a noise-only clip, like the stuff you see when your TV is badly tuned? Need the clip for an effect.

Tried to use my capture card for this, but everytime you detune, the card (or some driver thing?) just shows a completely blue picture.

card: WinTV GO
chip: Connexant 34881
software: VirtualVCR

Any suggestions,

Best, repo

[Malcolm]

simple.

connect your VCR to your TV-capture card. detune the VCR. capture the snow.

Greetings,
Malcolm

[repo]

Just tried this, and it still doesn't work. When the VCR starts to be semi-detuned the screen turns blue.

Any additional steps I could try?

Best, repo

[Arachnotron]

I think this is hopeless, since you need a Hsync signal to be able to cap. If you have only noise, there is no sync for the card to lock onto.

The only thing I can think of is to point a camera at your TV screen and capture that.

Maybe, just maybe you can switch something on on the VCR so the OSD activates and hope a few letters on the screen provide some sync, but I doubt it.

[trevlac]

How about ... record noise to VHS and then capture that.

[mustardman]

It sounds as though it is the VCR doing the "blue mute" as it is called. All modern VCRs and TVs do it, and it really pisses me off - a weak or variable weak signal may cut in and out of "blue mute". I can understand the audio mute, but the video as well! What a joke!

Both capture devices I have can capture pure noise (no sync at all). ADVC100 & DC30.

[repo]

Thanx for the input,

It's not the VCR that generates the 'blue mute', since I've tried various other configs which excludes this possibility. I'll try recording the noise with the VCR and then capture that.

Also send a ? to Hauppage. I'll let you know, if there's any valuable feedback.

Best, repo

[echooff]

The very beginning of the Sopranos has this effect. If you can capture the show you can duplicate the effect in either a loop or splice several copies together. Perhaps you have the dvd and can aquire it from there.

[repo]

Yep, and there's also the opening logo clip from HBO (like from Band of Brothers).

Thanx for all your input. Will certainly stick around here more actively in the future.

Best, repo

[joshyg2]

lol, thats funny.

ah, well all i know is that on my TV i can turn off the blue screen.
its called no signal detection blanking for something.

anyway, there should be a way of turning this off on your capture card. maybe its a hidden setting in the BT878/848 drivers.

[fellaw]

There are white noise filters for avisynth and virtual dub. Why not use one of these? Just use them as a mask for a clean source.

[mustardman]

Haven't heard of these. Do you have access to any links or names to search for?

MM

[trevlac]

Originally posted by mustardman
Haven't heard of these. Do you have access to any links or names to search for?

MM

I havn't used them, but look here.

http://www.indeus.com/sansgrip/avisynth/

Actually, an 'Outlawed' member pointed this out to me. ;)

[nosaj]

funny i was trying to get the same effect just the other day and was having the same problem. i did notice i reliably get the noise when i capture vhs and let the capture run longer than the tape. i think when the tape auto-rewinds after reaching the end is when i get the noise and then soon after it goes to the blue screen.

jason

[fellaw]

Yes, I meant the sansgrip filter available at the link posted above. It's for Avisynth 2.0. For use with Avisynth 2.5 use the LoadPluginEx.dll to load it. The zip file contains 2 dlls, one for uniform noise and one for gaussian noise.

I had one for VDub, too. Unfortunately, I couldn't find it and it seems to be down or offline. I looked at the filers links in vdub which point to nearly all sites with filters, but I didn't find it.

I'll retry a while, but I think you should stick to Avisynth.

[repo]

Hi,

Ended up doing this:

1. Generate 10 BMPs in PhotoShop with add noise filter on white background.

2. Read these into avisynth using ImageReader. Loop it to achieve desired length.

Looks pretty OK, and apparantly PhotoShop only seeds the random number once, so the 10 images are different.

Well, it's a hack, but I'm happy with the result.

repo

[mustardman]

Noise from an empty channel tuned on the TV looks substantially different from noise from a blank videotape.

The video-tape version looks brighter and the noise "stripes" longer. Perhaps gaussian noise at half image width (correct height though) and then stretched out to the correct size?

MM