Apple

thanks for the response. I will consider a convenience function. When you write convenience functions such as one like that, do you use it across multiple projects? If so, do you do anything to facilitate that? Just create a .c,.h and import the headers wherever? just curious. So I was finally able to get the audio file to write the data. I played back the file in finder and heard my voice sound checking and it was glorious.

I got it to work by changing the file type enum to CAF. I guess that my ASBD was not compatible with a wav file format although i'm not certain about that. Here was what I was using with wav and am now successfully passing in as the inStreamDesc when creating the ExtAudioFile.

// asbd for audiofile
AudioStreamBasicDescription fmt;
fmt.mSampleRate = 44100.0;
fmt.mFormatID = kAudioFormatLinearPCM;
fmt.mFormatFlags = kAudioFormatFlagIsBigEndian | kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
fmt.mBytesPerPacket = 4;
fmt.mFramesPerPacket = 1;
fmt.mBytesPerFrame = 4;
fmt.mChannelsPerFrame = 2;

My guess is that there is something in this that isn't compatible with the wav file formatting structure. Still, it'd be nice not to have to construct this at all. Passing in a reference to the audio stream that I have in my struct (which comes from the audio unit) also results in a fmt? error. That stream is obtained like so:

// set sample rate between input and output scopes equal and assign stream to player struct

propertySize = sizeof (AudioStreamBasicDescription);

CheckError(AudioUnitGetProperty(player->inputUnit,

kAudioUnitProperty_StreamFormat,

kAudioUnitScope_Output,

inputBus,

&player->streamFormat,

&propertySize), "Couldn't get ASBD from input unit");

AudioStreamBasicDescription deviceFormat;

CheckError(AudioUnitGetProperty(player->inputUnit,

kAudioUnitProperty_StreamFormat,

kAudioUnitScope_Input,

inputBus,

&deviceFormat,

&propertySize), "Couldn't get ASBD from input unit");

player->streamFormat.mSampleRate = deviceFormat.mSampleRate;

propertySize = sizeof (AudioStreamBasicDescription);

CheckError(AudioUnitSetProperty(player->inputUnit,

kAudioUnitProperty_StreamFormat,

kAudioUnitScope_Output,

inputBus,

&player->streamFormat,

propertySize), "Couldn't set ASBD on input unit");

I'm sure there is something in that as well that is not capable with the wav format. Anyway, CAF files are suitable for now. I would still like to know why WAV was such an issue.

fmt.mBitsPerChannel = 16;

On Thu, Jan 14, 2016 at 9:53 PM Christian Rober <email@hidden> wrote:

Alexander,

Let's definitely try to resolve that error first... If you are getting that error from ExtAudioFileCreateWithURL then my guess is that the ASBD you are passing in does not match the enum type you are also passing in. In other words, if you pass kAudioFileWAVEType to the create function, then your ASBD should probably look something like this:

{
AudioStreamBasicDescription streamDescription = {0};
Float64 sampleRate = 44100;
int channels = 2; // Do you want Stereo?
streamDescription.mSampleRate = sampleRate;

streamDescription.mFormatID = kAudioFormatLinearPCM;

streamDescription.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;

streamDescription.mBytesPerPacket = 4;

streamDescription.mFramesPerPacket = 1;

streamDescription.mBytesPerFrame = 4;

streamDescription.mChannelsPerFrame = channels;

streamDescription.mBitsPerChannel = 16;
}

That is just one way to do it (bordering on too manual IMO). I thought there were handy MACROS for this in the SDK but maybe I am conflating that with something else...

Minor related suggestion: consider creating this ASBD as a return value from a static function, it may be handy in the future... it was for me.

Lastly, and just for completeness: In terms of the client property, it should probably match the audio buffers you intend to pass into the WriteAsync functions and not necessarily the format of the WAV file itself. In your snippet you seem to be re-using the ASBD, which may not always apply.

--Christian
On Thu, Jan 14, 2016 at 7:43 PM, Alexander Bollbach <email@hidden> wrote:
Thank you for the help.

Fokke, I have since changed the way i set the stream for my audio file. You can that in this gist.

Christian, I have tried setting that property but since doing that I am now unable to create the audiofile. In fact that might have been the problem to begin with as I was not checking the OSStatus of
ExtAudioFileCreateWithURL. I now see that I get a 'fmt?' .. but if you take a look at that Gist I have no idea what could be the reason. In the convenience function CreateInputUnit I get the stream off the audio unit and set it as a member var in my struct. This is what I use to instantiate the ext audiofile but it doesn't seem to like the stream/'fmt'.

On Thu, Jan 14, 2016 at 3:19 PM Fokke de Jong <email@hidden> wrote:
HI Alexander,

I just answered you on stack exchange, it think there is something wrong with your stream description. There might be more, but you should check that first.

best,
Fokke

On Jan 14, 2016, at 17:31 , Alexander Bollbach <email@hidden> wrote:

no one?

On Wed, Jan 13, 2016 at 5:47 PM Alexander Bollbach <email@hidden> wrote:
I am still unable to write audio samples from my AUHAL's input callback to a file. I have tried a number of things including using the asynchronous version of writing to an audio file in ExtAudioFileServices. Even wrapping the call in a dispatch queue in fear that it was going out of scope. Even though it is probably some small obvious thing that is missing (i'm only a few months into using core audio) I posted a stack question about it. Apparently other uses have gotten the (-50) error. That is indeed the error I get. (you can run the GitHub Repo in xcode to verify this). I've been casually trying to get this to work over the past few days and I'm not getting any results. Any idea what I might be doing wrong?

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