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OAS Audio API

Windows Vista & Windows 7

This page summarises any issues reported and/or discovered by OAS which affect Playout running on the Windows Vista (and probably Windows 7) operating system. These are relatively new OS's and we have seem some subtle differences encountered when running Playout on this platform which are not apparent on previous versions of Windows.

Enhanced mode display issue (fixed in v3.31)

In Playout version 3.2x or 3.3, when running on a display which supports Playout in it's enhanced mode (1280x1024), the window appears to be shifted up the top of the screen such that the scrolling message is hidden from view.

The display from Vista is shown in the left of this image, with the correct positioning in the right hand image.

This problem only occurs using the default Vista display scheme or the "aero" scheme. A workaround is therefore to use the "classic" colour scheme.

Note this issue also occurs with Windows XP using the standard XP display theme.

'Beep' when tracks are selected

The PC speaker emits a beep when a track is selected in Playout main 'Load Dialog' or any of Playout Manager's editors. This occurs even if you have disabled sound effects and/or muted the PC speaker.

This is a known problem with Vista, a full description of the cause and workaround(s) can be found here.

"Fixed" in v3.4 since this release utilises the new common controls DLL which does not exhibit this problem.

Application "Not Responding"

During periods of processing - eg. a large music import, Vista can erroneously indicate that Playout Manager has stopped responding, "whitening" out the application - see below:

The reality is the application is working correctly it is just "busy". This condition is caused due to changes in the way Windows Vista monitors the status of running programs.

Fixed in v3.4

Licensing

Versions of Playout earlier than v3.07 will not run under Vista if the user is not part of the administrators group.

Default Playout database

The default database will be installed to:

C:\Users\Public\{Public }Documents\OnAStickSoftware\OAS Playout\

Prior versions of Windows located the database (and as such is the location used in the online help) in:

C:\Documents and Settings\All Users\Documents\OnAStickSoftware\OAS Playout

Sound architecture differences

Windows Vista has a somewhat different sound architecture to previous versions of Windows and this may (although unlikely) cause some issues with Playout, particularly on lower spec machines.

OAS Playout offers two distinct mechanisms for audio playback:

  • DirectSound is the default sound interface used which is provided as a standard sound layer by Microsoft, ideally providing a near direct interface to the sound card driver. It generally works well with most commercially available cards (Creative SoundBlasters etc.) and on-board devices. However more professional cards (such as some of the M-Audio series) do not work as well - at least as far as interacting with Playout goes.

  • ASIO provides the alternative sound interface designed specifically for use with professional cards, providing a low latency interface to the sound card driver. It has been supported since OAS Playout v3.1.

Windows Vista has a completely re-written audio layer, which coupled with other changes in the OS appears to incur a higher latency to the sound system no matter which interface you opt for ("Why Vista sounds worse", The Guardian). So this can mean that a system which runs perfectly under XP may not perform at the same standard under Vista.

DirectSound

Of more significance however is that Microsoft effectively made DirectSound obsolete in Vista, it is provided in a cut-down form (which does not appear to affect Playout) as an emulation layer into the new architectural model. This means that the direct, often hardware accelerated interface into the sound driver is not available in Vista, the upshot being that you may notice significant degraded performance over XP when using this interface.

In general it is probably not noticeable on a reasonable spec, modern PC. For the most part, Playout is only playing one or two tracks simultaneously which shouldn't be too onerous. The areas I'd expect to be troublesome though are when playing tracks which are not at the 44khz/stereo standard because they need to be converted to this prior to playback and without hardware acceleration this can be quite CPU intensive.

Future

At present there are no plans to adopt Playout to utilise the new audio stack architecture in Vista, at least not until the OS becomes significantly more prevelant.

Jon Bird, January 2009

 

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