heavy clipping distortion on 24-bit export

[vinylivo]

Just recently I realized that there is some 'problem' while exporting to 24-bit WAV files.

I was using 'Format:Other uncompressed files' and then selecting WAVE and 'signed 24 bit PCM' in the options dialog for export.
unfortunately I didn't realize that there were clippings in the project (actually just recently discovered the 'View:Show Clipping' menu item) because they were probably only very slightly, perhaps some 0.1dB over. after reopening and listening to the sound I heard some extrem nasty distortions for very few and short moments.
when zooming in at those distortions I saw that the sound had like signal inversion, looked like if the waveform who was touching the upper limit just continued from the lower (negative) limit. this sounds really bad and I didn't expect something like this. sounded like in the old opamp times where bad circuit designs coud lead to smilar behaviour when overdriven. normally I expect that clippings are just limited the hard way, but not signal inversion. interestingly, when I export a clipped file (not that I do this normally, there are limiters ) to 16-bit WAV or mp3, this doesn't happen. It's just hard limited the expected way.
this problem looks like related to some kinda overflow in the 'other format' export options, of course you can avoid it if you know before. but still it would be nice if integer outputs would just gracefully hard limit instead of inverting the signal. I guess this is a general 'bug', but I'm on OSX and can't test this on a windows machine.

PS: also, by using 'other uncompressed files' export, dithering doesn't work. so there's no dither from a 32-bit float project when I export to 24-bit WAV. this is perhaps not such a serious problem because all accumulated noise of the original project will be by far higher than the 24-bit dither noise.

[steve]

I believe this bug has been fixed in the current alpha version, so will become available in the next beta release.
In the mean time, the "workaround" is to ensure that your audio does not exceed 0 dB before you export. For single track projects, use the Amplify effect, and that will automatically set an amplification level so that the peaks do not clip. For multi-track projects, use "Tracks menu > Mix and Render" to mix the tracks into a single track before you export.

I think there is also another slight bug in Audacity 1.3.12 (and some earlier versions) that causes a very slight error in the conversion from 32-bit to 24-bit. If you really need to export 24-bit files you may be best to install the alpha version of Audacity (available here: http://wiki.audacityteam.org/index.php? ... tly_Builds

[vinylivo]

Hi Steve,

you're right, I just checked latest nightly build 1.3.13 and this bug is gone.

I'm using 24-bit PCM for archiving purpuses. My workaround is using 24-bit flac, this also ensures correct dithering and saves space. Thanxs.

I really love Audacity, especially because you can so easily program your own plug-ins via nyquist. simple text file, no IDE necessary. just great!
the only thing I miss in the effects menu is some ordering, to go thru such a large list is not so funny. luckily my OS supports menu entry selection by typing the name (if you know it) via keyboard once the effects menu is open. there was once a version with some ordering but this was skipped later.

[steve]

the only thing I miss in the effects menu is some ordering,... there was once a version with some ordering but this was skipped later.

The plan is that this will return at some point in the future, though it will almost certainly need to wait 'till after the release of Audacity 2.0.
The initial attempt to apply effect menu ordering was unsuccessful - for may users that have relatively few plug-ins, the way that menu ordering was implemented involved a lot more key presses for achieving common functions. There are ideas for improving effects menu ordering without creating inconvenience to the majority of users, but Audacity is in "feature-freeze" until 2.0 is released, so we'll just have to wait.

I really love Audacity, especially because you can so easily program your own plug-ins via nyquist. simple text file, no IDE necessary. just great!

Same here. If you've not noticed yet, we have a forum board for questions and discussions regarding Nyquist: http://forum.audacityteam.org/viewforum.php?f=39 If you've come up with any good plug-ins or snippets of Audacity code, feel free to post them there - I for one would be very interested to see

[kozikowski]

There are ideas for improving effects menu ordering without creating inconvenience to the majority of users

One of the ideas to make the system much more efficient was to hot assign individual effects to hot keys. Do you use Noise Reduction 200 times (and it's not that hard), then assign it to a key.

We all groaned when they took our tall pile away from us. Instead of sliding 2/3 of the way down and clicking (many multiple times), we had to dig through menu layers, pretty much killing efficiency. After the palace revolt, they gave us our single pile back.

Koz

[steve]

Instead of sliding 2/3 of the way down and clicking (many multiple times), we had to dig through menu layers, pretty much killing efficiency. After the palace revolt, they gave us our single pile back.

Which is fine if you've only got a few plug-ins, but pain when there's dozens or hundreds. To keep the list to a manageable size I normally have VST and LADSPA plug-ins disabled and only enable them when I need them, but it's a major inconvenience to have to go into Preferences > Effects, enable LADSPA, save the current project, restart Audacity, reload the project (and loose all the Undo history) if I need to use a LADSPA effect. It's a balance between doing that or having an additional 90 plug-ins in the list.

[kozikowski]

The solution is intelligent management of filters, not just reordering, stacking, or piling in layers. Hot Keys, a Most Used Corral, or Favorites.

Koz

[steve]

Hot keys would be nice, but it does not solve the problem of scrolling through 200+ effects to try and find that particular reverb effect that you used last month. Much easier to just look in the "Reverbs" section of the Effects menu.

200+ effects
24 built-in effects,
Filters - low-pass, high-pass, notch, band, parametric, FFT, IIR, dynamic filters, comb filters, resonant filters ....
Reverbs - lots of different sounding options here,
Chorus effects - lots of different sounding options here,
Sequencer effects,
Mixer effects,
Dynamic processors - gates, inverted gates, compressors, limiters, expanders...
Wave shapers,
Distortion effects,
Simulation effects,
Impulse convolution,
Pitch shift effects,
Multi-band dynamic processors,
Various "special" effects,
Repair and Restoration tools...
....

It's easy to build up a sizeable collection of useful tools.
What we don't need is the hassle of navigating through menus, sub-menus and sub-sub-menus to get to that effect that we use 20 times in one project.

[vinylivo]

I see this disussion get's somewhat OT. but me too like to add something about the effects menu ordering...

Why not create subfolders in the audacity plug-ins folder?
then people can organise it themselves. just read the structure and contents when the app starts. plug-ins in the 'root' of the plug-ins folder will be listed directly for fast access. and a certain folder structure can be generated on installation as a guide. of course empty folders should not show up in the menu.