Bit perfect editing

Effects, Recipes, Interfacing with other software, etc.
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Re: Bit perfect editing

Post by Alonshow » Thu Nov 23, 2017 3:34 pm

First off, I forgot to show appreciation for your answers a few years ago, so thank you for your help.

Second, I know that this is a very old thread, but I have a little question about it that doesn't really require a new thread:
steve wrote:Importing or exporting 32 bit float WAV format is completely lossless but the file size is huge.
Is it also lossless to import and export 16 bits WAV format? I'm currently using a recorder that saves the audio files in 16 bits WAV by default, so it would be very handy if it is.

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Re: Bit perfect editing

Post by kozikowski » Thu Nov 23, 2017 4:08 pm

There are recording apps that skip silences automatically. I have just downloaded one of these, and if it works well I will be using it from now on.
How would you know?

Let me read this back to you. If the software fails to record me reliably at night, I'll know not to use it any more.

Silent Sense programs all have sensitivity settings. Nobody's bedroom is completely silent, so the software has to decide which sound is normal background and which are performance. Throw normal microphone noise in there and chance of reliable recording is very poor.

You could double record. One recorder has the software on it and the other works the way yours does now. Play them both and if the new software performs as you want, start using it.

Otherwise, you'll never know.


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Re: Bit perfect editing

Post by Alonshow » Thu Nov 30, 2017 3:38 pm

Ah, don't worry, I dealt with that problem long ago. You're correct, of course. If I set the sound threshold too low, the recorder detects and records even the slightest noises. If I set it too high, the recorder misses some of my sleep talking. But it hasn't been a big deal for me because I don't really need to record 100% of my sleep talking. 80% or so is just fine. So I set the sensitivity to a medium spot and it works pretty well for me.

Still, even using the silence skipping feature I end up with audio files that last between one and two hours because, as you said, my bedroom is not completely silent, so the recorder still records plenty of noises. Only about 5% of the recording is useful, the rest is just noise. So I edit the file manually to select the 5% that is useful and remove the rest. I want to do that editing in a lossless (or bit perfect) way. I can do that with WaveShop, but it's a pain because it's not remotely as user friendly as Audacity, so I've ended up doing it with Audacity. However, I'm concerned that Audacity might be doing that in a lossy way, introducing recompression and distortion. Hence my question: Does Audacity import and export the 16 bits WAV format in a lossless or a lossy way?

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Re: Bit perfect editing

Post by steve » Thu Nov 30, 2017 4:26 pm

Alonshow wrote:import and export the 16 bits WAV format in a lossless or a lossy way?
That question is not as straightforward as it might appear.

The short answer is that it is lossless, but with caveats:

Audacity works internally in 32-bit float format. When converting from a higher bit format to a lower bit format, "dither" should normally be applied so as to avoid "quantize errors" (rounding errors).

When importing a 16 bit file, by default Audacity will convert the audio data to 32-bit float, which is a lossless conversion (essentially just padding the data with some zeros).

When exporting to a 16-bit file, Audacity converts the 32-bit float data to 16-bit integer, and by default Audacity applies "dither". Dither may be turned off in Audacity Preferences if required, but normally it should be enabled for best audio quality.

More information about dither:
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

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