It is a misleading message. Audacity has detected that the recording has stopped, but is not aware that it stopped prematurely.
If Audacity tries to use two different Hosts at the same time, then recording will stop within a few seconds and you will see that message. The message is actually correct - it is just informing you that Audacity has compensated for "latency". The problem is unrelated to the message - the problem is that recording has stalled.
Without using the PulseAudio Volume Control it is difficult to see exactly what is going on, and there are many possibilities. The most likely scenario is that Audacity is trying to access one device through PulseAudio and a different device through ALSA (your USB device and your ordinary computer sound card).
Here's some possible configurations for you to try. Go into Audacity "Edit menu > Preferences > Devices" to make the changes:
Host > ALSA
Playback Device > Default
Recording Device > Default
This should set Audacity to use PulseAudio and PulseAudio will then control which physical devices are connected to Audacity.
Host > ALSA
Playback Device > hw:0,0
Recording Device > hw:0,0
This should set Audacity to communicate with your computer sound card through ALSA
Host > ALSA
Playback Device > hw:1,0
Recording Device > hw:1,0
This should set Audacity to communicate with your USB device through ALSA
The above set-ups are not guaranteed as your system may be different from mine.
The main advantage of using PulseAudio is that PulseAudio allows you to record sounds that are playing on your computer. For example, you can play streaming audio in Firefox and record directly into Audacity without using a microphone or linking the output socket to the input socket with a lead.
The disadvantage to using PulseAudio is that it is possible to configure PulseAudio to use settings that are invalid, for example to try and record from an input that does not exist.
To set up PulseAudio,
- Set Audacity to use the Default recording and playback devices (on some systems Pulse is specified, on others there is just the option for "Default").
- Click on the Recording meter in Audacity to activate it (or right click on the meter and select "Start Monitoring)
- Open PulseAudio Volume Control and go to the "Recording" tab.
- You should see Audacity listed (probably "ALSA Capture") and there is a little down arrow at the right of it.
- Click on the down arrow for a drop down menu and select "Move Stream"
- Select your desired input (The Mobile-Pre USB - do NOT select "USB Monitor")
- Now switch to the Playback tab - there should be nothing listed apart from "System Sounds"
- Go to Audacity and generate a 30 second tone (Generate menu).
- Press "Play" and then "Pause"
- Now back to the PulseAudio Volume Control - you should now see Audacity listed in the playback section.
- Use the drop-down menu to move the output stream to the required device (probably your USB device, but choose whichever you want).
Audacity is now set up.
These settings should persist unless you change them, although if you use Skype it is possible that Skype could change the settings without telling you.
In PulseAudio Volume Control you can set the default recording and playback devices. Just go to the "Input" and "Output" tabs and use the drop down menus to set which input and output you want as the default.
The PulseAudio Volume control does not set individual inputs and outputs on audio devices, it just deals with the device as a whole. For example, on my computer sound card I have a built-in microphone and an external microphone socket. PulseAudio Mixer does not control these, it just controls the sound card as a whole. I would use the ordinary Gnome Mixer to select which microphone I wish to use.