TOPIC
In system software versions previous to Mac OS 8.1, the Monitors & Sound (or Sound) control panel provided a Playthrough checkbox to allow or disallow playing the sound of any audio source through the speakers. This option was typically used to listen to audio CD's. As of Mac OS 8.1, this option is no longer available in the Monitors & Sound control panel. Why was this option removed?
DISCUSSION Every application that utilizes audio input has the responsibility of configuring the sound input driver for use by the user. Unfortunately, there are some applications that rely on the user settings in the Monitors & Sound control panel instead of managing audio themselves. From a technical standpoint, it has become increasingly difficult for Apple to maintain global audio settings through the Monitors & Sound control panel while also allowing "well-behaved" applications to set them up locally. For this reason, the Monitors & Sound control panel now provides for the selection of a "Sound Monitoring Source". Any audio source chosen from this pop-up menu will always play through the sound output port (internal speakers, external speakers, or headphones). What implications will this have? Any application that uses a microphone for sound input should provide options for the user to configure the audio settings. A simple QuickTime dialog can be used if the application is using QuickTime to record sound. If the application does not provide a way for the user to configure audio, the user will have to select Sound In from the Sound Monitoring Source pop-up menu in the Monitors & Sound control panel and the sound from the microphone will play through the speakers. If the volume is too loud, this may cause a feedback loop. In this situation, the user can turn the volume down or plug something into the headphone jack, redirecting the sound from the speakers and preventing the feedback. The same situation will also occur with Apple's PlainTalk Speech Recognition software. Are there any workarounds? Any user experiencing this problem with an application should contact the developer and ask that they upgrade the application to offer control of the audio input through QuickTime. In the short term, the user can try turning the system volume down or plug something into the headphone jack to prevent feedback from the microphone from occurring. Note: The following contains information about software not written by Apple Computer. Apple does not make specific recommendations on third party utilities nor does Apple support or assume liability for any problems incurred by the use of third party applications. The following is merely mentioned for informational purposes as it may serve as a workaround for customers needing to disable playthrough either globally or for specific programs that do not yet offer the ability to disable playthrough. At the following website, there are a pair of small applications that allow you to toggle the Playthrough status on and off: http://ic.net/~platkus/ftpsite.html Apple has received reports that this software is effective. |
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| Document Information | |
| Product Area: | Mac OS System Software |
| Category: | Mac OS 8.1 |
| Sub Category: | General Topics |
| Keywords: | kalley, kmos81, supt |
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