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24-bit Audio Sounds Fine in Recorder, Distorted on Computer


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#1 Derek Diggler

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Posted 26 January 2010 - 10:48 PM

I have a Marantz PMD-670. When I record audio in 24-bits (regardless of sampling rate: 96kHz, 88.2 kHz, etc), it sounds fine playing it back in the Marantz, but when I transfer the file to any computer, it sounds ridiculously scratchy and distorted, and the waveform in ProTools reflects the scratchiness and distortion as well.

Here's a sample (24/96):
http://ext.glowingpi...rantz_24bit.wav

And a 16/48 recording from the same recorder:
http://ext.glowingpi...rantz_16bit.wav

What do you think? As I said, it plays back fine in the recorder. Some have suggested it's a dithering problem, but a) I can playback 24-bit stuff from other sources with no problem and B) I can't open it "clean" in any editor to be able to dither it down to anything else.

It's very irritating. Thank you for any insight.

Edited by Derek Diggler, 26 January 2010 - 10:50 PM.

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#2 Phil Rhodes

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Posted 27 January 2010 - 08:53 AM

Yeah, there's something wrong with that. I've loaded it into Goldwave, which I know supports 24-bit WAV since I've used it many times with a Fostex FR-2 compactflash recorder, and the 24-bit version is covered in hash. Same in Premiere Pro.

I've done quite a bit of programming with WAVE files but on examining the internal structure there doesn't really seem to be that much wrong with it; the only slight oddity is that the header specifies a two-channel left/right mapping for what is a mono file, but I can't see that this would put much software off. Otherwise it just appears to be a perfectly normal modern wave file with 24-bit three-byte data in it. Nothing special at all.

rifffile.png

I also tried a bit of byte reordering on the main data, because it's quite easy to make mistakes with WAVE formatting for 24-bit data, but (as I suspected) they haven't made such basic errors here.

I would therefore suspect that the problem is baked into the sample data itself and there may be a fault with the audio circuitry in your recorder, but I don't know for sure.

P
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#3 Paul Bruening

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Posted 27 January 2010 - 01:51 PM

It kinda' sounds like a bum connector or wire. Or is your connecting wire hanging over something that could add that noise? Sometimes it's a little thing.
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#4 Derek Diggler

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Posted 27 January 2010 - 02:19 PM

Phil: My goodness! Thank you for all that effort dedicated to my problem! It's good to hear that I'm not crazy. I noticed my firmware wasn't up to date so I'm sending it in to get updated, do you think that could solve the problem? Or do you think it's certainly a hardware issue?


It kinda' sounds like a bum connector or wire. Or is your connecting wire hanging over something that could add that noise? Sometimes it's a little thing.


No, the XLR wasn't crossing over any wires or anything. This happens consistently when I try it out in the field and everything (and with much nicer mics :))
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#5 Saul Rodgar

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Posted 27 January 2010 - 03:32 PM

How are you transferring the problem audio to the computer, via analog or digital?

If it sounds good on playback from the Marantz outputs and you can hook that up to your Pro Tools interface, then I'd do that. Even though it won't have the convenience of USB transfer. it'll work for the time being . . .

We used that recorder a few years back for a S16 short and I don't recall any issues with it, but I was DP so it wasn't quite my dept.
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#6 John Sprung

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Posted 27 January 2010 - 03:54 PM

OK, I gave them a try. I downloaded both and opened them with the freeware version of Audacity (version 1.2.6). Level is extremely low on both. In Audacity, I used Effect-Amplify on both. The 16 bit needed 28.2 dB's, but sounded OK -- within the limits of a pair of little Altec Lansing computer speakers. The 24 bit needed 22.2 dB's, and had a constant low level hiss throughout.

That it plays right on the recorder, and that with a little help one of them works in Audacity, means that the sound is getting into digital form OK. Something is screwing it up in the digital file realm. It's getting scaled way down, and that hiss may be a misguided attempt at dithering.

Definitely check out Audacity and its forums. You're more likely to find someone there who knows the issues with this recorder.






-- J.S.
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#7 Derek Diggler

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Posted 27 January 2010 - 04:01 PM

How are you transferring the problem audio to the computer, via analog or digital?

If it sounds good on playback from the Marantz outputs and you can hook that up to your Pro Tools interface, then I'd do that. Even though it won't have the convenience of USB transfer. it'll work for the time being . . .


It records to a flash card, so I've just been copying the WAV files from the card to the computer. For a previous project (a film) where the audio guy ignored my warning and recorded 24/96, I did indeed connect it analog to my M Audio device and played it back from the Marantz (since again, it plays back fine from the Marantz itself), and that proved to be hours of painstaking work. ;)

That's certainly an option for recovering recorded audio, but I just wanted to make sure it's not my fault that I can't just copy the WAVs over.
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