Getting Max Headroom-type stutter in Audacity

I use Audacity to make poetry recordings for podcasts. I’m occasionally getting a stuttery effect, much like Max Headroom, when I’m recording.

I’m using Windows XP. Audacity 1.2.4. Emachines laptop.

Max Headroom does Yeats! Grr.

Any ideas?

Hm. It sounds like it could be a couple of things. One is a sound card driver issue. But if you’ve recorded before without stuttering / skipping / repeating in the file, then it’s unlikely that a driver issue has all of a sudden come up.

How about the state of your hard drive? Is it full up, or getting close? Do you regularly defragment? It sounds plausible to me that your drive might be so fragmented that the write head has to search all over the disk to find little spaces to write, causing gaps or glitches in the recording. I’ve seen that problem before.

If it’s not this, then sorry, I don’t know. But that might be it. Hope I could help.

Sound buffer. Specifically, it isn’t big enough. This is a hardware failing. Generally, what’s happening is this:

A small amount of audio data is read into the sound card’s audio buffer. The size of this buffer will depend on the card, but typically with older and/or lower-end cards, it ain’t much. Playing CD quality stereo audio results in approximately 88k of audio data per second (44.1K x 2 channels). Sound cards might have 128k or 256k or more, again, depending. The buffer is just temporary storage; the computer still has to issue a command for the sound card to play what’s in its buffer and to continue to feed it with an audio data stream. If the computer gets busy, it may neglect to feed it more audio data. The sound card, having not received any further orders or data from the CPU, is left to just twiddle its thumbs, so it just repeatedly plays what’s in its buffer until it’s told to do otherwise. This results in a small hunk of audio playing over and over again until the CPU has freed itself from whatever it was distracted with and carries on feeding it with more audio.

Being that this is a hardware failing, there’s not much you can do to fix that end of it short of buying a higher end sound card, but you can avoid it by simply not giving the CPU more to do than it can comfortably handle without getting distracted. To that end, close any open applications that may chew up CPU cycles or do frequent/extended writes to the hard drive (which itself unduly command the CPU’s attention, since it gives pretty high priority to disk access.) Simple things that just sit there - mail checkers, IM programs, MP3 players (unless your CPU is REALLY slow) and so on are fine as they aren’t very demanding. Just don’t run too many active (read: needy programs that do lots of things, or lots of one thing) programs simultaneously or the cumulative effect will cause the stuttering to return.

Also, as fishbycicle alluded to, if you have a smaller amount of memory (256 megs, or 512 megs if your audio stream is huge) and are low on disk space or high on disk fragmentation, there may be a lot of virtual memory swapping going on, and as I said, disk access is pretty demanding on the CPU’s attention. Defrag, clear up some space, whatever you need to do if you feel this may be a factor.

Missed the edit window. Wanted to correct the spelling fishbicycle.

So: fishbicycle.

Also, by “hardware failing,” I meant that it is a limitation of the hardware, not that the hardware is, in fact, failing.

(It’s late. I’m tired. I’m full of excuses.)

What quality of audio are you recording? A few things can reduce the amount of work that the computer has to do while recording.

The first step will be to record in mono, since I would guess you don’t have a stereo microphone and don’t need stereo effects in the reading. After you record, duplicate the track and make it stereo (so your listeners can still hear it in stereo). This is in the Preferences (Options on Windows?), under Audio I/O.

The other options are reducing the quality level. You can go lower than 44.1 kHz (though 16 kHz is probably the lowest I’d go), or reduce the sample size to 24-bit or 16-bit from the default 32-bit. I’d keep it higher if you do any processing on the audio after recording, though.
If you need any more help with doing this, let me know.

Thanks for the ideas. I will have to check all my settings tonight against what you are all suggesting and see if I can find the culprit.

It hasn’t always done this, so that would lean toward a fragmentation type issue, right? I do generally record with Firefox running, but no other programs.

I think the hard drive is nearly empty on that thing, but it’s possible I’m wildly mistaken.