Device Toolbar
- Peter 23Sep13: Looks ok to me - removed the P2
- Peter 3Oct13: WDM-KS host has been removed wef 2.0.5 alpha r12630 2Oct13.
- Peter 7Oct13: WDM-KS host will not be in 2.0.5, removed the P1.
Using the drag handle at right, you can expand Device Toolbar rightwards to be wider than the default width shown, or drag it leftwards to be less wide. You can hover over any of the four boxes at any time to see the full text for the selected item.
Audio Host
Selects the particular interface with which Audacity communicates with your chosen playback and recording devices.
On Windows, the choice is between the following audio interfaces:
- MME: This is the Audacity default and the most compatible with all audio devices.
- Windows DirectSound: This is more recent than MME with potentially less latency.
- Windows WASAPI: This host only appears on Windows Vista, Windows 7 and Windows 8. The only inputs that are currently provided are "loopback" inputs for recording computer playback. 24-bit recording devices are supported. Output is emulated using this host. As a result, the output slider in Mixer Toolbar will only scale the system output slider's current level up or down rather than directly manipulating that system slider.
ToDo-2 will need to restore this if and when WDM-KS support is added back to Audacity.
- Windows WDM-KS: "KS" stands for "kernel streaming" which achieves low latency through bypassing the kernel mixer that is normally used to mix outputs from multiple applications. You may be able to achieve latencies as low as 5 milliseconds by reducing Audio to buffer in Recording Preferences until the sound breaks up, then slightly increase the buffer. When recording overdubs at such low latencies, you'll need to either set the default latency correction in Recording Preferences to zero, or take our Latency Test to set the optimal correction value. 24-bit recording is supported.
Under WDM-KS, only one application is allowed to access the audio device at a time. So for example if you are already playing audio in the web browser or another application, you will not be able to play audio in Audacity using the same device that the other application is using.
On Mac OS X the only choice is Core Audio.
On Linux there is often only one option: ALSA. Other options could be OSS and/or Jack Audio Connection Kit (also known as "Jack" or "Jackd").
- On Windows XP or earlier (given a recent computer), DirectSound's much shorter path to the hardware should produce much lower latency than MME.
- On Windows Vista, Windows 7 and Windows 8:
- Windows DirectSound may by default have only slightly lower latency than MME.
- Selecting Windows DirectSound or Windows WASAPI and enabling both "Exclusive Mode" boxes in Windows Sound allows Audacity to request audio direct from the device without resampling.
ToDo-2 will need to restore this if and when WDM-KS aupport is added back to Audacity.
- On Windows XP or earlier (given a recent computer), WDM-KS's and DirectSound's much shorter path to the hardware should produce much lower latency than MME.
- On Windows Vista, Windows 7 and Windows 8:
- Windows DirectSound and WDM-KS may by default have only slightly lower latency than MME. However WDM-KS can produce latencies as low as 5 milliseconds if you reduce "Audio to buffer" in Recording Preferences as described above.
- Selecting Windows DirectSound or Windows WASAPI and enabling both "Exclusive Mode" boxes in Windows Sound allows Audacity to request audio direct from the device without resampling.
- When using WDM-KS, the currently playing application has exclusive access to the audio device irrespective of Windows "Exclusive Mode" settings. See the Wiki page for Windows 7 for more explanation.
Output Device
Choose the built-in or attached sound device that you want to use for playback.
In the image above, "Microsoft Sound Mapper - Output" appears when the Windows "MME" Host is selected. The "Mapper" output is not a separate device, but is the device from the output list that is currently chosen as the default system playback device in the Windows Control Panel. When "Windows DirectSound" Host is selected, the device that maps to the current Windows playback device is called "Primary Sound Driver".
In most other cases (for example, the inbuilt computer sound device), each entry for output device consists of the output type (such as speakers), followed by the name of the audio device the output belongs to.
Input Device
Choose the built-in or attached sound device that you want to use for recording. Input sources are no longer chosen in Mixer Toolbar.
In the image above, "Microsoft Sound Mapper - Input" appears when the Windows "MME" Host is selected. Similarly to the "Mapper" output, the "Mapper" input is the device from the input list that is the current default Windows recording device. When "Windows DirectSound" Host is selected, the device that maps to the current Windows recording device is called "Primary Sound Capture Driver".
In most cases (for example, the inbuilt computer sound device), each entry for input device consists of the input type (such as microphone), followed by the name of the audio device the input belongs to.
If a device only has one possible input for selection by the computer (for example, a USB microphone), only the name of the device will be listed, with no input type.
Input Channels
1 (Mono), 2 (Stereo) or the number of channels that are provided by the drivers of your sound device. On most inbuilt sound devices, especially on Windows, only mono or stereo will be available. For some devices on Windows, choosing Windows DirectSound in "Host" above may be more likely to reveal options for recording more than two channels. On some devices capable of recording more than two channels, an explicit "multi" device may appear in the "Device" drop-down for recording all the channels simultaneously.
- If your input is mono, such as most microphone ports for the inbuilt sound device, selecting "2 (Stereo)" in Input Channels duplicates the mono source to both channels, merely producing a dual mono recording.
- If your input is stereo, then as well as setting Input Channels to "2 (Stereo)", ensure any settings in the system or sound device control panels are stereo. Many input devices on Windows Vista, Windows 7 and Windows 8 default to mono recording even if they are stereo devices. To correct this, follow these instructions.
