Re: AVFoundation and Core Audio integration for capturing
Re: AVFoundation and Core Audio integration for capturing
- Subject: Re: AVFoundation and Core Audio integration for capturing
- From: Orestis Markou <email@hidden>
- Date: Sat, 04 Aug 2012 23:01:38 +0300
After some testing, I may have found a solution for syncing the two files - use the first mHostTime in the render notify callback for audio, and the "com.apple.cmio.buffer_attachment.hosttime" attachment value in the first CMSampleBufferRef of the AVCaptureFileOutput delegate callback.
However, I have stumbled upon a show-stopper: Running an AVCaptureSession (even with just the camera, no microphone input/connection) effectively disables my Audio Graph. Is this a known limitation or should I file a bug?
I'm using an external Focusrite Safire 6 USB sound card and the built-in Macbook Pro iSight camera, on Mac OS X 10.8
Any help on this would be greatly appreciated.
On 4 Αυγ 2012, at 2:52 μ.μ., Orestis Markou <email@hidden> wrote:
> Hello,
>
> I have the following use case, for Mac OS X 10.8:
>
> 1. An audio unit graph that mixes audio input and file-based audio and applies real-time audio unit effects. Nor very different from a karaoke backing track that you sing along via a microphone.
>
> 2. A video camera that records video of the person singing.
>
> I need to produce a video file that will combine the video and the audio. I have managed to write those to individual files using an AUGraph render notification and ExtAudioFile APIs and an AVCaptureSession. I don't need more than 30ms accuracy, but it needs to be somewhat guaranteed, i.e., no occasional 300ms offsets because of timing issues.
>
> First question: Can I record the tracks together from a combined API? Perhaps by routing the AUGraph into the AVCaptureSession.
>
> Second question: If there isn't a way to record those tracks together, can I somehow add timing information to them so that I can sync them up manually?
>
> I saw various new APIs added to AVFoundation for 10.8, but it seems they are playback only (e.g. the master clock).
>
> If this isn't the correct mailing list to post this, please direct me to an appropriate one.
>
> Thanks,
> Orestis
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