Clearing up the sound on a low quality avi recorded with a Casio EX-Z57?

April 28, 2006 10:40 AM

Clearing up the sound on a low quality avi recorded with a Casio EX-Z57?

Some teenagers made off with one of my neighbour's moped scooters last night. A passer-by walking his dog spooked them and they abandoned it round the corner. They couldn't start it so a load of them had been carrying it. Later that evening some teenagers were sitting on the wall outside our house, and I could hear one, on the phone, asking some friends where they were. He definitely eyed up the scooter in the yard, and my neighbour later said that the cover of her scooter, a different one, might have been disturbed. My neighbours thought we should go downstairs to make some noise, but I took a few moments before that to record them on my camera. They were talking very quietly however, and so it's very hard to make out what's being said. Curiosity has gotten the better of me, though, so I'd like to find out if they said anything incriminating. I got a good look at them later, but didn't get their faces on video; but it'd be handy to know if they came back that they are the ones responsible. It's not the first occasion someone's been at the mopeds either.

I've spoken to the police and have no intention of taking the law into my own hands yada yada etc etc sensible sensible...

For the curious and helpful, I've uploaded a 10Mb zip file of the videos to yousendit. I fear a little whispering on my part interferes with the sound in the second.

Is there anything I or anyone else can do to clear up the speech?

posted by nthdegx to Technology (7 answers total)

I asked a similar question and got some answers that might help you.
posted by blue_beetle at 12:12 PM on April 28, 2006

Cool edit (now audition) and Audaciity (haven't used this) have an amplitude function that will give you volume, if that's neccessary. The best part is the noise reduction, though. There are a few tips on how to use this out there (in cool edit you match the two lines up, you'll see) and you should have no trouble finding one with google. First, though, you'll need to strip the audio with this, following these instructions.

Play with the noise reduction and other filters for something useable, though it's fairly difficult at times.

There is also software that's purpose made for this type of work, but it can be expensive (search for audio forensics).

Good luck! And don't ask me how I learned any of this. (Oh, except stripping from AVI's. That was a two second goog search.)
posted by IronLizard at 12:20 PM on April 28, 2006

On listening, that will probably be absurdly difficult even though the filters I mentioned are damn near purpose built for removing that kind of hiss, but good luck. The audio artifacts produced by noise reduction will probably drown out any kind of conversation that can be gotten from that, especially with the low bitrate that's done in. But then, this is interesting so I might just give it a whack tonight.
posted by IronLizard at 12:31 PM on April 28, 2006

Ok, using the tools available to me, this is impossible. Sorry. Next time, rig a directional mic with a parabolic reflector. Or, as one guy did, stick an electret into a pvc pipe.
posted by IronLizard at 12:49 PM on April 28, 2006

I'm not at home so can't try this myself yet (and haven't listened to the recordings yet), but try boosting the eq in the vocal range and lowering it in the hiss ranges?

I can give it a look/listen when I get home in a couple hours, but if it's as bad as it seems to be, you really can't do much.
posted by ruby.aftermath at 1:18 PM on April 28, 2006

Oh man, you've got nothin'. Sorry.
posted by ruby.aftermath at 3:53 PM on April 28, 2006

Response by poster: Wow, thanks for trying everyone. I'll take you up on your advice and have a go myself, for fun as much as anythig as it sounds like I won't have much luck!
posted by nthdegx at 7:07 AM on April 30, 2006