Audio Help Needed

Some people might have realised the lack of new mixtapes in my blog already. The good news: I still like music, I still like Drum’n’Bass and I still like DJing. The bad news: recording got more difficult.

Up until now I used a small python I script I wrote to record the mixtapes. It basically just wrapped around

gst-launch-0.10 pulsesrc ! queue ! audioconvert ! vorbisenc ! oggmux ! filesink location=<somefile>

Nothing really exciting there. As I mostly do ~one hour mixtapes, I also made it print out when I started recording and I used python-mutagen to tag the whole work afterwards and put the playlist into a comment. So far so good – the script always worked out for me.

I use my laptop for recording: it’s easy to carry it around and just place it next to the decks and just plug the line-out into the microphone jack. I don’t have a special sound card, up until now the standard thing (Intel Corporation 82801H (ICH8 Family) HD Audio Controller (rev 03)) was good enough for me.

Some time during Jaunty, I had trouble because the recording audio levels changed. Sound was all fine when I used a headset and things like Skype, but when I plugged the cable from my mixer into the microphone jack sound was absolutely distorted. I resorted to writing a small script using alsctrl (re)store to have something similar to “audio profiles”.

So far so good. The next problem I ran into was a weird feedback loop that resulted in odd noise in the recordings. I tweaked the “profiles” some more and muted a couple of other channels. Unfortunately this was more time-consuming than I thought. You’d think there’s not much “real channels” in a standard laptop. Whatever… fixed that problem too.

Yesterday I spent an hour to record another mixtape – I thought it was quite good actually. The really odd thing: the sound level changes drastically after around half an hour of the mix. It goes really quiet, then after a minute goes up to the original level again, a minute later same thing again. Over and over.

HELP! What could possibly be wrong there?