Generation Loss in AUP to WAV to Aup to Wav?

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Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by hellosailor » Fri Dec 26, 2008 7:15 pm

I'm recording my AUP files from high end cassette, and using 16-bit 44k "CD" quality for the recordings.

My intentions were to keep the AUP files as masters, then burn off lossless WAV files (fome home listening) and VBR MP# files for portable listening.

And then it struck me, is there any reason to keep the AUP files? Or will the WAV files faithfully contain ALL the same data, so that I could reconvert them into AUP files in the future without any signal degradation is I needed to use AUP files again?

(Sometimes I'll use the Audacity tools to clip bad lp pops or do other light processing. Right now I need to transfer the tapes and "get 'er done" but I don't want to cut off my chances of going back to 'full quality" files in the future, for more source work.)

So...is it really useless to keep the AUP files if I have lossless WAV, both made at 44k/16bit/CD quality? Or would second-generation AUP files loose just a tiny something?
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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by Gale Andrews » Fri Dec 26, 2008 9:13 pm

If your Default Sample Format in the Quality Preferences is 16-bit and you are recording at 44100 Hz sample rate, then yes exporting as PCM WAV 16-bit 44100 Hz should be identical to the audio in the project _data folder.

If your Default Sample Format was 32-bit Float, then you would have to export as 32-bit float WAV to keep all the data. This type of WAV would not burn to an audio CD and might not be playable by all software players. If you then exported as 16-bit WAV, the audio in that WAV will not be the same as the 32-bit audio in the _data folder because it would be downsampled, using Dither to control the resultant distortion.

My preference though would be to record in 32-bit float if you intend to edit the recordings. This will retain the dynamic range and signal-to-noise ratio during editing, and this quality retention would generally outweigh any perceived loss from dithering down to 16-bit in the exported file. In any case processing in Audacity of the floating point values used in 32 bit is quicker than processing the fixed integer values used in 16-bit.


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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by hellosailor » Sat Dec 27, 2008 12:17 am

Very interesting, Gale. Previously I'd only heard people say that using 32-bit was excessive and wasted when the source material was CD-quality or less. Some of these tapes are close to CD quality--but they're still a bit less.
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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by kozikowski » Sat Dec 27, 2008 12:44 am

<<<My intentions were to keep the AUP files as masters,>>>

See, now. That went right by everybody. No, you're not. Guaranteed.

The AUP file is an Audacity Project Management file. Not a sound file. You can open it up in Windows NotePad and read it.

This is a really simple AUP Project File
http://kozco.com/tech/audacity/aup1.jpg

It's in XML which is a sorta-English programming language.

It's job is to point to the thousands of other files that make up your project. Move or change any one of those thousands of files--or move the AUP file itself, and your show turns to dust.

The only way to get one single, stand-alone, top quality sound file is to Export As WAV, aside from all the bit depth considerations. The rule is to produce those Capture Master WAV files at the highest quality you can--which Gale pointed to earlier. You can always go downhill from there.

http://audacityteam.org/forum/viewtopic.php?f=12&t=3150#p12375

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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by hellosailor » Sat Dec 27, 2008 12:54 am

Koz, use a little telepathy like everyone else, wouldya?<G>

When I said the AUP files, I meant all of Audacity's files, including the data files that the AUP files work from/with.

So, if I really need to rephrase the question? Wav are enough? Or keep the AUP and data files as well, for any reason?
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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by kozikowski » Sat Dec 27, 2008 1:13 am

<<<Koz, use a little telepathy like everyone else, wouldya?<G>>>>

Sorry. Crystal ball's in the shop. Do you have any idea how hard it is to get parts for one of those? Don't ask how I knew it was broken...

<<<When I said the AUP files, I meant all of Audacity's files, including the data files that the AUP files work from/with.>>>

And in the original directory structure. Few people have any idea how brittle Audacity Projects are.

I don't use Projects. Ever. I export each live capture as a WAV. If it's a critical show, I make copies onto a portable drive. Finish editing and export the final show to another WAV. I have never lost a show (knock on Formica®) unlike the many people who arrive on the forum wanting us to revive their damaged or destroyed Project.

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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by hellosailor » Sat Dec 27, 2008 1:34 am

Huh. Well, if WAV is god enough to keep as the "master"....you've just doubled my hard drive space.

Crystal ball parts? No problem, ask any steampunk, there's bound to be one nearby with suitable spares.<G>
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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by kozikowski » Sat Dec 27, 2008 1:53 am

<<<you've just doubled my hard drive space.>>>

The person who normally objects to this is on holiday, so I'll need to do it. If you have a multi-track show (over 2) you have no choice but to try and save the Project. There are no reliable or convenient ways to Export one of those. Sixteen tracks, no problem. Export as eight different WAV files. Ewwwww.

<<<ask any steampunk>>>

Oh, mine isn't broken. It's my grandfather's. The last time they made parts for it was in 1924. It's unstable enough as it is. I'm not going to use knock-off parts. Not...Happening. Besides, if you tried to put either of these around your neck, they'll be picking you up off the floor.

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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by Gale Andrews » Sat Dec 27, 2008 7:41 am

There are a few pieces of information stored in projects which you can't store in the WAV. One is labels (created with CTRL + B, or CTRL + M when playing or recording) at points or regions in the waveform. Even here though, some editors that support an extension of WAV called Broadcast WAV can read and write markers in WAV files (maybe Koz knows more about those than I do)? Another is envelope points:
http://audacity.sourceforge.net/onlineh ... velope.htm

Note that when 1.4 becomes the new stable version next year to replace 1.2, it will open 1.2 projects but once you save that project in 1.4, it will no longer be openable in 1.2.

kozikowski wrote:If you have a multi-track show (over 2) you have no choice but to try and save the Project. There are no reliable or convenient ways to Export one of those. Sixteen tracks, no problem. Export as eight different WAV files. Ewwwww.


You can in 1.3 Beta (and 1.4 when it comes out) export multi-channel WAV, AIFF, OGG or FLAC files, which gives you a way to save multiple tracks without saving as a project. Multi-channel export is enabled on the Import / Export tab of Preferences by checking "Use Custom Mix" in the "When exporting tracks..." panel. You can have up to 32 output channels for WAV, AIFF or OGG and 8 output channels for FLAC. There is no support for exporting multi-channel files when using File > Export Multiple, though. Nor is there is support at the moment for multichannel playback - a multi-channel file in Audacity will always be mixed down to stereo.



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Re: Generation Loss in AUP to WAV to Aup to Wav?

Permanent link to this post Posted by waxcylinder » Sat Dec 27, 2008 12:19 pm

Ok my two penn'orth on this subject.

As Gale suggests above, I record and edit in Audacity with Audacity set at 44.1kHz 32-bit floating (so I get the extra headroom). I export to WAVs at 44.1kHz 16-bit. I make backup copies on two separate external USB drives (very cheap these days- just bought an Iomega 1TB for a mere UK£97). I also burn a CD or CDs of the project (most of mine are LP or tape transcriptions) - and import the music into iTunes/iPod as AAC.

Then I can remove both the Audacity project and the WAV files from my PC's hard drive freeing up valuable working space).

This produces excellent CDs and iPod tracks - and I do occasionally re-import the WAVs into Audacity for further editing, which works fine.

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