Recording at 24bit appears to be 16 bits padded to 24bit

[thunderstick]

The "DirectSound" choice for SoundBlaster that Thunderstick is using in the Audacity Audio I/O Preferences might be the key here, as the other choice (MME) only supports 16-bit recording (even with 24-bit hardware).

Gale

Hi Gale. I can record with MME support in 32bit with no problem. My posting above (with the screenshot) shows that my right channel has samples in the -115dB range. This file was created with MME support, not DirectSound. Thus, it proves the file is not 16bit. As well, eharmonica (the op) tested both MME & DirectSound files I created and both were 24bit. Just fyi.

thunderstick.

[Gale Andrews]

Hi Thunderstick

Thanks - OK I've seen it now - both MME and DirectSound produced 24-bit (your post top of page 3).

I did "think" I could recall someone using MME to get "true" 24-bit recording in the past with 24-bit hardware, so I did not chime in before now, but another developer saw this thread recently and remarked "WMME drivers on Windows is restricted to 16-bit" then pointed out that the Direct Sound *API* supported 24-bit recording. I don't think anyone's really discussed precise drivers they were using here. So maybe the point is that (for example) properly written 24-bit WDM drivers will produce 24-bit recording in Audacity even using MME, but other drivers (such as Enharmonica's) will only produce 24-bit recording with DirectSound?

Let's see if I can get some clarification...


Gale

[eharmonica]

Just to finish up.

Thanks, Gale, for noticing my thread and for your input.
I've kinda moved on after switching to Cool Edit Pro. My "funtime" is limited and checking everything out was taking up too much of it

I am using the latest EMU drivers when I record.

[Terry]

I just checked and find I have the same problem as eharmonica.... When I look at the samples using the trial version of Adobe Audition, the FLAC files I recorded with Audacity (supposedly at 24 bits / 96 kHz), line up on the grid values and never between, showing that they are really not 24 bit samples. They are 16 bit samples. When I check 24/96k flac files I downloaded from HDtracks, the samples fall in between grid values (mostly), showing that they are indeed 24 bit samples. I am using a Creative Sound Blaster Audigy 2 sound card with the latest drivers.
Is there anything I can do to get Audacity to record in true 24 bits?
Is this a known bug that is being worked on?

Terry

[Gale Andrews]

I just checked and find I have the same problem as eharmonica.... When I look at the samples using the trial version of Adobe Audition, the FLAC files I recorded with Audacity (supposedly at 24 bits / 96 kHz), line up on the grid values and never between, showing that they are really not 24 bit samples. They are 16 bit samples. When I check 24/96k flac files I downloaded from HDtracks, the samples fall in between grid values (mostly), showing that they are indeed 24 bit samples. I am using a Creative Sound Blaster Audigy 2 sound card with the latest drivers.
Is there anything I can do to get Audacity to record in true 24 bits?
Is this a known bug that is being worked on?

Terry

From what we can see (despite some of the reports here) the code used by our PortAudio Audio I/O interface simply doesn't record at more than native 16-bit on Windows, due to limitations in PortAudio. See.
http://audacity.238276.n2.nabble.com/24 ... 05042.html


Gale

[Terry]

Wow,
No discussion of this since march?? I would have thougt this is a pretty major issue.

Terry

[steve]

I would have thougt this is a pretty major issue.

Not really. The only people to notice the problem are those that look very closely at the waveform.
For best quality sound you should do all processing in 32 bit on 32 bit tracks, but the difference between starting with 24 bit audio and 16 bit is very very small. The most noticeable difference between 16 bit and 24 bit audio is the lower noise floor of 24 bit, but in real world recordings the noise level from other sources is almost always considerably higher than -96dB.

Yes, it would be nice to get 24 or 32 bit recordings from 24/32 bit hardware, but doing everything else right you can still get excellent recordings without it.
There's some stuff on the Internet that suggests that, with appropriate hardware, higher bit depths are available (with Portaudio) on Linux, so one workaround could be to use Linux.

[Terry]

Steve,
Thanks for takng the time to explain this to me. I've already wasted many frustrating hours trying to get it to work, so it is good to at least know that it isn't going to work.

I did try recording some 24 bit (at 96kHz) using the application that comes with the sound blaster audigy cards (Wave Studio 7), then pulling them into Audacity as wave files, editting them, and saving them off as flac. This preserved the 24 bit resolution, so at least the Audacity can handle the 24 bit samples, it just can't record them.

Given the proliferation of 24 bit sound cards, I'm suprised this isn't considered important enough to fix. Can you even buy a sound card that only supports 16 bit recording anymore? Hopefully this will get fixed some time. Audacity is a great tool otherwise.

Terry

[Terry]

Should this be reported as a bug (or has it already)? The home page says that Audacity can record at 24 bits. No mention of the bug.

Terry

[steve]

Yes the developers are aware of the issue.
Audacity can record in 24 bit, it's just that on Windows, the data will be 16 bit padded to 24 bit. As far as I know this issue does not affect Linux or modern Mac computers.