Re: DisplayCodecSpecificSettings

On Jun 8, 2007, at 10:34 AM, Michael T. Luongo wrote:

You guys are all the greatest on this forum! You are so helpful and quick to respond. If it weren't for people like you we would all be scratching our heads not knowing how to get the last piece of the code finished. You guys are amazing! Maybe one day I could become a fulltime mac developer. Until then I have to program on windows, poor me :(

I just wondered if you guys could help me out with one of my problems. I am trying to figure out what to send to DisplayCodecSpecificSettings.

I read over this article http://developer.apple.com/qa/qa2006/qa1437.html

I guess what I am trying to do is get the list of options available for a format like MAC6 or MAC3. If you could just tell me what I should be sending the function or write up some psuedocode it would be of tremendous help.

They have no options. But essentially:

open scaudio component

If you have an input format from which you'll be converting, set the input basic description property.

Set output asbd with format set to MAC6 or MAC3. You can leave all the fields set to zero in the asbd that you don't know. But at a minimum, you probably want to fill in mFormatID, mSampleRate, and mChannelsPerFrame. So, for instance:

out.mFormatID = 'MAC3';

out.mSampleRate = 44100.;

out.mChannelsPerFrame = 1;

QTSetComponentProperty(scAudio, kQTPropertyClass_SCAudio, kQTSCAudioPropertyID_BasicDescription, ... &out, ... )

now get the kQTSCAudioPropertyID_CodecSpecificSettingsArray property.

You won't get one for MAC3 unless your input and output sample rates don't match, in which case you'll get some sample rate conversion settings (quality, etc).

If you want to make ui for supported sample rates (common to all formats), use the kQTSCAudioPropertyID_AvailableSampleRateList and kQTSCAudioPropertyID_ApplicableSampleRateList properties.

If you want to make ui for supported channel layouts (common to all formats), use the kQTSCAudioPropertyID_AvailableChannelLayoutTagList/kQTSCAudioPropertyID_AvailableChannelLayoutTagNamesList and kQTSCAudioPropertyID_ApplicableChannelLayoutTagList/kQTSCAudioPropertyID_ApplicableChannelLayoutTagNamesList properties.

If you want to list all the available encoders on the system, use the kQTSCAudioPropertyID_AvailableCompressionFormatList/kQTSCAudioPropertyID_AvailableCompressionFormatNamesList properties.

-Brad Ford

QuickTime Engineering

References:
	>DisplayCodecSpecificSettings (From: "Michael T. Luongo" <email@hidden>)