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Old April 25th, 2005, 08:37 PM   #1
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audio quality

I'm wondering weather the 384kbps mp2 audio that the HD100 records to tape will actually be usuable where you're filming a live concert, or maybe some wildlife or a choir or anything that requires really decent audio quality and that you might want to process and then put back out to tape?

my concern is that in practice when distributing on DVD the audio will be compressed twice. Once by the HD100, then uncompressed, processed/mixed and then compressed again to DVD. what is that going to sound like?

secondly will the HD100 be upgradable so it records stereo 16/44 PCM as in the full HDV spec? It would be a pain to have to carry around a seperate recorder whenever audio quality is important.

finally does anyone know what the mic preamp spec is for the HD100?
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Old April 27th, 2005, 11:47 PM   #2
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Frankly I don't see (or hear) any issues with 384kbps audio, Joe, but I'll ask Ken Freed if he could please chime in about this. Keep in mind that although the audio is compressed, the video is compressed even more, and it still looks great. The issue is not compression, but rather the quality of the codec used in the compression. Thanks for your patience,
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Old April 27th, 2005, 11:57 PM   #3
 
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I'm not Ken Freed...., but....Recompressing the MPEG1/LayerII audio isn't as big a deal as it seems IF, and that's a HUGE "IF" it's recorded properly.
where the MPEG audio will bite you in the butt is if you record levels too low. it's not forgiving like PCM more or less is. MPEG audio ain't for the amatuer, it's for the guy that's spent a little time practicing with his gear, knows how it responds with mics, line inputs, and so forth.
The only time you *might* notice an issue with the MPEG is when you are recording extremely dynamic music, and you record too quietly. Cymbals in an orchestra will "sizzle" as they fade out, because of the aliasing that will occur at low levels. There are tools to repair that if you're unfortunate enough to have it happen.
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Old April 28th, 2005, 12:57 PM   #4
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I agree with Douglas
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Old April 28th, 2005, 09:30 PM   #5
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cheers for the info guys. I guess I'll have try compressing some wavs twice with mp2 384 and seeing what I think. But it sounds like from Doug's mention of symbols and aliasing, for recordings where you want to capture that sense of 'air' and space of a location that comes from low level detail in the higher frequencies then a seperate recorder will be necessary. The Sound Devices 722 looks very good for such purposes and will doubtless have much better audio preamps than the HD100 (it's slightly over spec'd doing 24bit 96Khz and costs almost half of the HD100, but then you KNOW your audio will be well taken care of) and there's also the Core Audio PDA based solution with the same paper spec (less some pro features) which is more economical. But then for day to day use I'm sure the mp2 will be fine.

I realize that HDV video is very compressed, but I think with audio lossy compression makes more difference to the feel of the material. But then I work much more with audio than video at the moment so that probably biases my opinion.

Finally, I don't understand why they couldn't have used PCM instead of mp2... itn't it part of the HDV spec?
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Old April 28th, 2005, 09:45 PM   #6
 
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PCM is not part of the HDV spec, no.
Frankly, I've worked with this a LOT, and as an audio geek, I don't find it nearly as problematic as I expected it to be. In fact, it was the audio that got me to seriously look at the camera. On paper, 384Kpbs audio sucks. Plain and simple. In everything we've been taught, and I was taught by the very, very best in the digital audio world, compression is not ever a good thing.
But the truth is, it sounds just fine. No, it doesn't have the air of a good 24bit/192k recording, but it also doesn't carry the overhead, and more importantly, it just sounds fine. And when you factor in that *most* of the audio that's going to be captured with these cameras is dialog, it's a total non-issue, and anyone who tells you otherwise is ignorant. Mathematically, it's not as good, no. But mathematically...we'd never be in outer space, either.
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