Weak audio in HVR-Z1U - Design Flaw?
 

Hello.. Just got back from demo'ing the Z1U in Denver. One interesting tid bit, is that the audio bandwidth for HDV is 384kb vs 1.5mb in the DV spec.

Maybe this has been discussed before, but are any of you FX1/Z1U users out there experiencing any audio issues (low quality after re-compression etc..) ?

matt rickman

HDV Audio is Mpeg 1/Layer 2, and is fairly compressed.
Compression isn't a bad thing. There are all sorts of rumors that it falls apart when recompressed. Hogwash, most of it.
yes, there are compromises, but the only place they are significant is in the extreme frequencies, and even then, you'll only notice it on "tails" such as when recording in a church and there is a lot of reverb. As the reverb 'tails' out, you might hear some crunching if you're wearing headphones. Dithering will cure this.
On capture, most NLE's use an intermediary, or "DI." This DI will convert the audio to a wav or aiff format, and you'll edit like normal audio. It recompresses to MP3, Ogg, AC3 just fine, I've done a lot of testing. Sony Vegas has a batch converter that can take the same audio file and render/output to many formats for testing purposes. This was discussed to death in the Now Hear This forum, but it seems that a lot of folks aren't understanding you won't be/shouldn't be editing the native MPEG audio file. If you are....get another NLE. Or find a workaround.

I think the real test would be further compression. In your scenario it should hold up fine, but in further compression (which usually isn't necessary) from what the sony people were saying, the file would "fall apart" I don't think this is so much of a practical limitation as it is a theoretical limitation.

I guess the idea is if you took a piece of audio and compressed it to a .wav and then compressed it to an .ac3 and then converted that back to a .wav. The file would not "hold up" as well as a DV clip run under the same procedures.

Again, I don't think this matters in practical terms, and I am fully aware that these were the sacrifices made to allow more video bandwidth.

Douglas do you have this camera?

matt rickman

I have two Z1's, I've had my first Z1 since mid November when they announced it. It's a prototype, but it's the one I used to write the HDV book with. I've done just about every audio experiment with the cam one could do.
It's not the same consideration as the AC3 back to wav, but I see where you're going with that. I HAVE compared, at sample level, the original and the DI format, and it's not enough different to matter.
If you transcoded again, and then tried going back to .wav/aiff, it would be compromised, but likely not all as bad as folks say. "Theoretical" seems to be the buzz phrase for shooting at this camera, but it's rare you'll find anyone who's actually done the work agreeing with the "theoretical" naysayers.
It sounds good. (not great) I don't like the DACs in most DV cams anyway...so I'm a bit of a snob.

douglas,
thanks for the insight...

How has your experience been with dropouts with the camera. I don't know if you read my post in the long black line about using the digital master tape or not, but sony was painting the picture that you can expect to have problems with standard dv tape.....

matt rickman

Hmm...I don't know that I've seen/heard Sony present the position that you'll have dropouts with standard tape, but rather that they've got a new tape that offers much greater protection against dropouts.
I've shot a lot of footage, mostly test stuff, but have been free of any dropouts thus far. But for me, I'm not one to take those risks. I'll pay the extra few bucks for the safety net.

What tape are you using?

I think this statement was made based on using standard sony dv tape (premium). Although there is no reason why HDV would have more dropouts than DV, so I didn't quite understand why they were pushing the new tape so hard (well I know WHY they were.. but it doesn't, to me, have any technical merit).

matt rickman