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AVAssetWriter / AVAudioPlayer Conflict?

listingboatlistingboat Posts: 55Registered Users
in iPhone SDK Development
Weeks ago, I posted this thread regarding problems I was having with AVAssetWriter: http://www.iphonedevsdk.com/forum/iphone-sdk-development/81747-avassetwriter-woes.html

Further research seems to lead to a conflict using AVAssetWriter while playing audio with AVAudioPlayer or, really, any audio system. I tried with OpenAL as well.

Here's the background:

- Using AVAssetWriter to write frames to a video from an image or set of images works fine UNTIL [AVAudioPlayer play] is called.

- This only happens on the device, not the sim.

- The error occurs when attempting to create a pixel buffer from CVPixelBufferPoolCreatePixelBuffer.

- Once the audio starts playing, the AVAssetWriterInputPixelBufferAdaptor.pixelBufferPool which existed before suddely becomes nil.

You can download the representative project here: TestAVMethods.zip

Comment out AVAudioPlayer play and it will work on the device.

Any clues are appreciated.
Post edited by listingboat on
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Replies

  • listingboatlistingboat Posts: 55Registered Users
    I've found the solution to this issue.

    If you want to have AVAudioPlayer and AVAssetWriter behave correctly together, you must have and audio session category that is 'mixable'.

    You can use a category that is mixable like AVAudioSessionCategoryAmbient.

    However, I needed to use AVAudioSessionCategoryPlayAndRecord.

    You can set any category to be mixable by implementing this:

        OSStatus propertySetError = 0;

        UInt32 allowMixing = true;

        propertySetError = AudioSessionSetProperty (
                               kAudioSessionProperty_OverrideCategoryMixWithOthers,  // 1
                               sizeof (allowMixing),                                 // 2
                               &allowMixing                                          // 3
                           );
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