Audacity Forum

There is a problem that I currently have with Audacity. Every so often, I hear extremely grating crackle/static on the playback. I find it frustrating. It is getting to the point where I feel afraid to use Audacity, because I often say four-letter words and pound on the desk every time.

The distro that I currently have is OpenSuSE 13.2. What other information would you like to know to help me solve this problem?

There are many possible causes for crackle on playback.
What sort of computer do you have?
What sound card?
How are you listening to the music?
Does it only occur with particular files?
If you try playing the same file another time, will it play OK?
Does it still happen if you turn down the volume?
Are you running other applications at the same time?
Does rebooting your computer (temporarily) fix the problem?
What steps have you taken to diagnose the problem?
Anything else that you can think of that may help to diagnose the problem?

Here are the cards installed in my computer:

card 0: NVidia [HDA NVidia], device 0: ALC888 Analog [ALC888 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 1: ALC888 Digital [ALC888 Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 2: ALC888 Alt Analog [ALC888 Alt Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: CODEC [USB Audio CODEC], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0

The computer I have is made from different parts, most of which were ordered from Newegg.com. I believe that I have 2GB of RAM installed in the computer. Perhaps more should be installed?

I can think of several things that may be going on. It is possible that Audacity may be having conflict with a few other programs. I am guessing that VLC and Firefox might be among those.

I might also be using a version of Audacity that is unstable. I can either get this program from the Packman repository or the regular one. I think I used the Packman one before, which I am guessing might be the more unstable one.

This crackle/static usually happens on some occasions whenever I attempt to do crossfade effects in an audio file, using more than one mono track. Perhaps I may not be doing this correctly. I usually choose "Add New Audio Track" from the Tracks menu whenever I want to do the crossfade or dissolve effect. I've read, though, that "Split New" from the Edit menu is what should be used for this.

Another possibility is that it has something to do with me occasionally using a track directly from video files. In some cases, the soundtracks are 48000Hz, as opposed to, say, 44100Hz. Perhaps I should make an audio-only track with 44100Hz first?

Whenever I check out an edit that I have just made, I also often play part of an audio for a very short time, like for only a few seconds. Do you think that might be causing the trouble I'm having as well?

One common cause of "crackling" is when the audio level goes above 0 dB. In digital audio* 0 dB is an absolute limit.
When two or more tracks play simultaneously, the amplitude is the sum of amplitudes in all tracks at that point. Thus it is easy to cause the peak level to exceed 0 dB when multiple tracks are playing, even when each of the tracks individually are well below 0 dB. If the audio exceeds 0 dB, the waveform is "clipped" on playback, which can sound like a "crackling distortion". When this occurs, the playback meter in Audacity will show that the level hits 0 dB and a "clip indicator" will show (see: http://manual.audacityteam.org/o/man/me ... l#playback).

The current version of Audacity is 2.1.1.
Unfortunately, some Linux distributions (notably "Ubuntu") built Audacity with the wrong version of WxWidgets, so their official version has a number of bugs as a result of that. They are aware of the problem and it should be resolved once Audacity 2.1.2 becomes available. You can check your version of Audacity by looking in "Help > About Audacity". The version number is at the top of the first tab. The version of WxWidgets should be 2.8.xx (where "xx" is at least 10). The WxWidgets version number is shown on the "Build Information" tab. Audacity 2.1.2 has not been released yet, but this requires WxWidgets 3.x.

What is your USB audio device?

Firefox will not normally interfere with Audacity unless you are critically short of RAM or disk space (2 GB should be adequate - I only have 3 GB on my machine and most of the time only about 1 GB is used). However, if you have had a page open that uses Flash player, then Flash will be running, and that may cause problems with other audio applications (Audacity). Some versions of Flash do not release the sound services correctly after use. Closing Firefox and restarting Audacity should fix this problem (temporarily).

If tracks are at a different sample rate than is supported natively by your sound card, then resampling must occur (either in Audacity, or somewhere within your computer's sound system. This places additional load on the system that may cause crackling. This is most likely on very old or under-powered hardware.

*Digital audio is usually 8, 16 or 24 bit "integer", which means that the amplitude of each sample is denoted by an integer number which is then "normalized" to a range of +/- 1. It is not possible to have a sample value outside of the range of +/- 1 because that is the point where you run out of "bits". For example, the range for 4 bit (binary) numbers is from 0000 to 1111 and that is all. An exception to this rule is "floating point" format audio. Internally Audacity uses "32-bit float" representation for representing sample values, and this does support values outside of the range +/- 1, but sound cards don't understand floating point, so the audio must be converted to "integer format" before being sent to the sound card, and that brings back the +/- 1 limit.

This is what I get when I run "lsusb":

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 004: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 002 Device 003: ID 08bb:2900 Texas Instruments PCM2900 Audio Codec
Bus 002 Device 002: ID 056a:0302 Wacom Co., Ltd
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

I think the "003" probably is the one that has to do with the USB audio. The number "002" is probably the drawing tablet, "004" is probably the wireless mouse, and the two "001"'s I am not sure of. The "Bus 001" ones are probably the front USB ports (which have nothing connected to them at the moment), and the "Bus 002" ones are probably the back USB ports.

I am aware of distortion if the sound is above 0dB, but I doubt that the volume of a sound file has anything to do with the current problem that I am having. I am guessing that it could be an overuse of hardware sources.

The version of Audacity that I currently have in my computer is 2.0.5. At the time that I wrote the first message, I believe I may have had version 2.1.1. At some point, I had installed Audacity from a different repository after writing the first message. The WxWidgets version that I currently have is 2.8.12.

Until recently, I had Kubuntu installed in my computer. After that, I switched to OpenSuSE, because I've read that many Linux distros have faulty forks of cdrtools in them. This past summer, I ordered and installed a Blu-ray burner into my computer. I have burnt two Blu-ray discs so far, and both times I received some sort of error messages when I used K3b for these processes, before switching over to OpenSuSE. I have yet to burn any discs using this distro.

I believe you are right about Flash affecting programs like Audacity. This is particularly noticeable after I go to a website like YouTube with the Firefox browser. In the past, I had problems with Audacity freezing, or with it playing audio really fast. This is because the audio source listed would switch over to "default," or something like that.

I think you are also probably right about too much additional load on the sources used while playing audio on Audacity, especially after using another program that may use some of the same sources.

What playback device do you want to use? Can you post the contents of Help > Audio Device Info... top right of Audacity? It might give us some extra clues.

When you open a new project window, what is the project rate bottom left?

What desktop are you using? If it's GNOME, I understand that OpenSUSE uses PulseAudio https://en.opensuse.org/SDB:Pulseaudio#Configuration. PulseAudio can be prone to freezing, cracking and skipping. That is what you experienced before when you chose "Default".

At its simplest, you can bypass pulse by choosing the (hw) device in Audacity's Device Toolbar.

Are you doing CTRL + W regularly to clear out Audacity's temp folder?


Gale

The Audio Device Info is very long. It looks like it lists as many as 15 different devices, with 15 as the default selection. Here is a small part of text that I saw. Please let me know if you want the entire text, which I pasted into a separate text file that I saved.

Selected capture device: 15 - default
Selected playback device: 0 - HDA NVidia: ALC888 Analog (hw:0,0)
Supported Rates:
44100
48000
96000
192000

The rate displayed at the bottom left is 44100.

The desktop environment that I am using is KDE4. There are times in the past when "default" is selected automatically by Audacity itself. This seems to occur after I use another program with sound source, such as VLC and Firefox.

I had recently read about switching to an (hw) device, but I still get the occasional crackle or static - especially when I begin to play a small part of an audio again.

I had never thought of trying the CTRL + W idea. I could always try that. That is a good idea.

cdikrunn84 wrote:The Audio Device Info is very long. It looks like it lists as many as 15 different devices, with 15 as the default selection. Here is a small part of text that I saw. Please let me know if you want the entire text, which I pasted into a separate text file that I saved.

Now you have done it, we may as well see it, if you don't mind. If you press the Code button above your message, then paste the information, it will be formatted nicely inside a scrolling box.


Gale

Gale Andrews wrote:Now you have done it, we may as well see it, if you don't mind. If you press the Code button above your message, then paste the information, it will be formatted nicely inside a scrolling box.
Gale

I have attached a text file that has the full list of these devices.

By the way, I have recently switched Linux distros again, from OpenSuSE to Ubuntu Studio, mainly because there seem to be limitations as to what one can do with FLV files in OpenSuSE. The Ubuntu-based distros have always been more familiar to me, in fact. So far, I have used Audacity a little bit in Ubuntu Studio. The only problem that I have run into, at this point, is Audacity freezing up once, and being forced to close the program. This has happened with me before, when I had used such distros as Kubuntu. I'll have to read up on how to avoid having Audacity freezing up every now and then.

Your list does not contain a pulse device, so was that list from when you still had OpenSUSE?

cdikrunn84 wrote:So far, I have used Audacity a little bit in Ubuntu Studio. The only problem that I have run into, at this point, is Audacity freezing up once, and being forced to close the program. This has happened with me before, when I had used such distros as Kubuntu. I'll have to read up on how to avoid having Audacity freezing up every now and then.

Ubuntu Studio uses PulseAudio, so see http://wiki.audacityteam.org/wiki/Linux_Issues#pulse.

You have never stated clearly what the USB device is (make and model number). Are you getting crackle on that, the built-in device, or both?


Gale