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?

This entry was posted in Drum'n'Bass, Music, Ubuntu. Bookmark the permalink.

11 Responses to Audio Help Needed

  1. luisbg says:

    have you tried to use the alsasrc or osssrc elements in gstreamer as the audio source to check it isn’t pulseaudio?

  2. > when I plugged the cable from my mixer into the microphone jack
    > sound was absolutely distorted

    Yes, microphone jack != line in.

  3. Dan Chen says:

    Ah, you’ve just added to my TODO for blogging about audio stack triaging. The list of culprits runs deep indeed, from alsa-lib and PulseAudio up through GStreamer.

    Firstly, are you using PulseAudio 0.9.14-0ubuntu9 (with libasound 1.0.18) from the main repository or 0.9.15~test3~ppa2 (with libasound2 1.0.19) from Luke’s (themuso’s) PPA?

    Secondly, if you’re using PA from the main repository, if you disable autospawn in /etc/pulse/daemon.conf, is the symptom reproducible?

    Thirdly, please run the debugging script at http://www.alsa-project.org/alsa-info.sh.

  4. ntfreelancer says:

    I too encounter same issues while recording via usage of mixtape. I can’t suggest u its solutions.

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