On Nov 29, 2014, at 2:31 AM, Ben wrote:
> I'm trying to get the video dimensions by using
> AVCaptureInputPortFormatDescriptionDidChangeNotification however the width &
> height returns a number way higher than I am expecting.
> Expecting 320/480 or similar but getting width = 1088784512, height =
> 1819304813.
>
> Any ideas what I am doing wrong?
>
>
> -
> (void)avCaptureInputPortFormatDescriptionDidChangeNotification:(NSNotification
> *)notification {
>
>AVCaptureInputPort * captureInputPort = notification.object;
>
>
>CMFormatDescriptionRef formatDescription =
> captureInputPort.formatDescription;
>if (formatDescription) {
>CMVideoDimensions dimensions =
> CMVideoFormatDescriptionGetDimensions(formatDescription);
>
>
> }
>
>
> Printing description of dimensions:
> (CMVideoDimensions) dimensions = (width = 1088784512, height = 1819304813)
>
>
>
> Printing description of formatDescription:
> {
> mediaType:'soun'
> mediaSubType:'lpcm'
> mediaSpecific: {
> ASBD: {
> mSampleRate: 44100.00
> mFormatID: 'lpcm'
> mFormatFlags: 0xc
> mBytesPerPacket: 2
> mFramesPerPacket: 1
> mBytesPerFrame: 2
> mChannelsPerFrame: 1
> mBitsPerChannel: 16 }
> cookie: {(null)}
> ACL: {(null)}
> }
> extensions: {{type = immutable
> dict, count = 1,
> entries =>
> 2 : {contents =
> "VerbatimSampleDescription"} = {length = 52,
> capacity = 52, bytes = 0x0034736f7774 ...
> 00020002}
> }
> }
> }
Looks like you’re assuming that the formatDescription is a
CMVideoFormatDescriptionRef, when printing it shows that it is a
CMAudioFormatDescriptionRef. I don’t have direct experience with the API, but
would guess that CMVideoFormatDescriptionGetDimensions doesn’t return any
useful value when passed a CMAudioFormatDescriptionRef.
As to why you’re receiving a notification for an audio format or input port
instead of the video format/port you’re expecting, that’s left to you to
determine.
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