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audio devices: use-cases

Carl: a power-user on the move

Carl uses his laptop for private use and work. He works at home, while travelling on a train, or at the office. He uses the following hardware:

  1. built-in HDA soundcard with jacks for headphones and a microphone, the laptop contains builtin stereo speakers and a surround speaker option in the mixer.
  2. a USB headset: simple usb-audio device with stereo playback and one microphone. It also has two buttons to increase/decrease the volume, sending the volume media keys keyboard events
  3. a monitor with built-in USB soundcard (usb-audio device which also contains a mixer device): stereo speakers, built-in microphone. Playback to the monitor speakers is also possible through HDMI (actually DisplayPort, but Linux reports that as HDMI). In addition the monitor also has a built-in webcam, which is attached with the same USB plug.
  4. A HiFi setup using a Cinch-3.5mm cable to connect its line-in to the laptop's headphone jack. The speakers are arranged such that the balance must be adjusted slightly to the right for a centered stereo sound where the laptop user sits.
  5. standard 3.5mm jack headphones (for use in the train, and sometimes also for use at the desk at home or at work)
  6. Alesis io|2 USB pro-audio soundcard. Carl uses this devices at home (or when he's working as sound-engineer) to record stuff. His favorite tool for this job is Ardour.
  7. At home Carl sometimes also connects his laptop to his TV and can use HDMI to use the stereo speakers of the TV for audio output.

When Carl does home-office he uses Skype, a SIP application, and a H.323 application (e.g. Ekiga for both SIP and H.323) to provide VoIP connectivity to his collegues and be reachable via a phone number that is not his private phone number. To provide the best sound quality he wants to use his USB headset when it's connected. If the headset is not connected he wants to be able to answer calls with the built-in speakers and microphone. When he then connects the headset, while in a call, he wants the sound to migrate automatically to the headset.

When at work, he wants to use the microphone and speakers of the monitor for VoIP applications. If he plugs a headphone in the 3.5mm jack of the laptop, he'd like to use that as the output device. On unplugging the headphone jack the output should migrate to the monitor again.

Event sounds (this includes ringing sounds of VoIP applications when being called) should go to

  • at work: to the monitor speakers, unless a headphone is plugged in, in which case it should go to both the headphones and the monitor speakers
  • at home: to the internal sound card/headphone jack and, if plugged in, additionally to the USB headset

Sometimes Carl uses his laptop to play a short round of Wesnoth against his friend, while talking to him on Skype. Thus he uses the USB headset for communication and wants Wesnoth to use the USB headset for sound output as well. Since the Wesnoth action is not always very high ;) Carl also starts up Amarok in the background and wants it to play to the headset, too. This requires to have the Skype output louder than the Amarok and Wesnoth "noise", because talking to his friend is most important to him.

Ami: a desktop system in the living room

Ami has her desktop computer on a desk in the living room. The internal HDA soundcard is connected to the monitor speakers via the 3.5mm front output jack and to high quality active speakers via the 3.5mm back output jack. She also has headphones with 3.5mm connectors which she can plug into either the headphone jack of the desktop or the headphone jack of the monitor. A USB webcam with built-in microphone is attached, providing the only microphone of this system, for use with Skype. The nearby TV is attached to the graphics card via an HDMI cable and can provide stereo audio output.

For most of her time at the computer, she only requires event sounds and the audio of web videos on her monitor speakers. If she wants to switch to higher quality playback, she turns on the active speakers and migrates the music and video audio to the active speakers while event sounds stay on the monitor speakers. To watch a DVD or some of her videos she uses the TV and either wants to use the TV speakers or the active speakers.

When using Skype, she wants to capture from the webcam and use the monitor speakers. But sometimes she'd rather move over to the couch and TV for a longer chat.

Implications for the GUI

Generally the system should be as smart as possible and provide the best defaults possible to minimize configuration tasks. What the computer can't recognize:

  • what kind of device is used when a 3.5mm connector is plugged into the headphone (or any line out) jack
  • ?

The following special events are possibly interesting for a smart audio device management to monitor and handle:

  • move video window from one monitor to another
  • reconfigure monitor setup (e.g. switch from monitor to TV output)
  • when a Skype/SIP/H.323 call is active and who is on the other side (friend vs. business contact)
  • incoming VoIP call

That leaves the following setup changes to manual intervention:

  • switch between headphone pan centered and slightly adjusted to the right
  • turn playback to different output jacks on/off (this might be configured as two or three setups which can then be recalled somehow)

This page was last edited on 10 August 2011, at 15:48. Content is available under Creative Commons License SA 4.0 unless otherwise noted.