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Re: iOS 8 ExtAudioFile AppleLossless distortion
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Re: iOS 8 ExtAudioFile AppleLossless distortion

  • Subject: Re: iOS 8 ExtAudioFile AppleLossless distortion
  • From: "Dave O'Neill" <email@hidden>
  • Date: Mon, 12 Jan 2015 10:30:55 -0800
Here is a helper function I use to get ASBDs. I use floats because they work with the accelerate framework and they are easier on the eye. When setting the kExtAudioFileProperty_ClientDataFormat property on your extAudioFileRef, you should use an ASBD for interleaved, and when setting ASBDs for audio units you should not use interleaved.  So in your case i would use this function to get ASBDs like this:

AudioStreamBasicDescription extAudioClientASBD = asbdWithInfo(1,2,1);
AudioStreamBasicDescription mixerInputASBD = asbdWithInfo(1,2,0);

AudioStreamBasicDescription asbdWithInfo(Boolean isFloat,int numberOfChannels,Boolean interleavedIfStereo){

    AudioStreamBasicDescription asbd = {0};

    int sampleSize          = isFloat ? sizeof(float) : sizeof(SInt16);

    asbd.mChannelsPerFrame  = (numberOfChannels == 1) ? 1 : 2;

    asbd.mBitsPerChannel    = 8 * sampleSize;

    asbd.mFramesPerPacket   = 1;

    asbd.mSampleRate        = 44100.0;

    asbd.mBytesPerFrame     = interleavedIfStereo ? sampleSize * asbd.mChannelsPerFrame : sampleSize;

    asbd.mBytesPerPacket    = asbd.mBytesPerFrame;

    asbd.mReserved          = 0;

    asbd.mFormatID          = kAudioFormatLinearPCM;

    if (isFloat) {

        asbd.mFormatFlags = kAudioFormatFlagIsFloat;

        if (interleavedIfStereo) {

            if (numberOfChannels == 1) {

                asbd.mFormatFlags = asbd.mFormatFlags | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked | kAudioFormatFlagIsNonInterleaved;

            }

        }

        else{

            asbd.mFormatFlags = asbd.mFormatFlags | kAudioFormatFlagIsNonInterleaved | kAudioFormatFlagIsPacked ;

        }

    }

    else{

        asbd.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked;

        if (!interleavedIfStereo) {

            if (numberOfChannels > 1) {

                asbd.mFormatFlags = asbd.mFormatFlags | kAudioFormatFlagIsNonInterleaved;

            }

            

        }

    }

    return asbd;

}


On Mon, Jan 12, 2015 at 8:49 AM, Robert Carroll <email@hidden> wrote:
Can I ask what data type you are using for your samples?

I replaced all references to AudioUnitSampleType with float this morning. That gets me correct playback on iOS8, but on iOS7 I get overloaded noise.
On iOS7 AudioUnitSampleType was working, as was SInt32.

I’m running this on 2 iPads with the two iOS’s. Testing the arch with #if __LP64__ shows 32-bit for both devices. I can try switching to a fixed width int as per Doug Wyatt;s suggestion. My preference is to find a structure that will run on both iOS’s.

rob


On Jan 11, 2015, at 8:31 PM, Dave O'Neill <email@hidden> wrote:

Are there any other audio units in your chain?  Be sure to set the output ASBD of each audio unit to the input ASBD of the audio unit it is connected to (downstream).  Just as a troubleshooting technique you can try putting AUConverters between various audio units to see if that fixes things.  Maybe you could post your ASBD and we can spot an issue.  Instead of using AudioUnitSampleType just find out what it is typedef'd to and substitute it with that ( you can just highlight it and "jump to definition" in Xcode).  All of the iOS8 specific issues I've had were all traced back 32-64 bit issues. Here is a handy guide that points out some common gotchas: https://developer.apple.com/library/ios/documentation/General/Conceptual/CocoaTouch64BitGuide/ConvertingYourAppto64-Bit/ConvertingYourAppto64-Bit.html#//apple_ref/doc/uid/TP40013501-CH3-SW1


On Sun, Jan 11, 2015 at 5:00 PM, Matt Hart <email@hidden> wrote:
I haven't tested with m4a lossless, but I have played about 14 or so lossless wav simultaneously as well as that many m4a compressed files. They are all buffered though.

On Jan 11, 2015, at 7:08 PM, Robert Carroll <email@hidden> wrote:

Hi.

Thanks. I am doing that with the same function call.

Further investigation is pointing to some other issue. My code that reads the ExtAudioFile objects is playing single m4a files, but not multiple files set up on different mixer buses. I was testing with a single A440.if file then with 3 m4a lossless files for C4, E4, G4 which should play simultaneously.

On iOS 7 it works, on iOS 8 I get a brief burst of vicious white noise. 

I’m inclined to think this is back to the storage type for the sample data. Since, I haven’t found an answer to a replacement for the AudioUnitSampleType on iOS, I had reverted my code to using that type.

rob

On Jan 11, 2015, at 6:25 PM, Matt Hart <email@hidden> wrote:

I use this with iOS 8 and 7 without any issues. Did you set the expected client data format onto the audio file property?

status = ExtAudioFileSetProperty(_audioFile, kExtAudioFileProperty_ClientDataFormat, sizeof(_targetAudioDescription), &_targetAudioDescription);


On Jan 11, 2015, at 1:56 PM, Robert Carroll <email@hidden> wrote:

I am attempting to narrow down the options why my audiograph code is failing on iOS 8. 

I am using ExtAudioFileRead to extract data from applelossless source files and load structs set up for this purpose.
The buffers and audioData parts of the struct are typed as AudioUnitSampleType.

All of this works as it should on iOS’s up to 7.x. Running on iOS 8.1.2 I can play aiff source files with this code but get distortion if I load the m4a (lossless) files.

What changed in iOS 8 with extaudiofile that would account for this issue?

thanks

rob


Robert Carroll
RSM Records
Toronto
http://www.rsmrecords.com


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  • Follow-Ups:
    • Re: iOS 8 ExtAudioFile AppleLossless distortion
      • From: Robert Carroll <email@hidden>
References: 
 >iOS 8 ExtAudioFile AppleLossless distortion (From: Robert Carroll <email@hidden>)
 >Re: iOS 8 ExtAudioFile AppleLossless distortion (From: Matt Hart <email@hidden>)
 >Re: iOS 8 ExtAudioFile AppleLossless distortion (From: Robert Carroll <email@hidden>)
 >Re: iOS 8 ExtAudioFile AppleLossless distortion (From: Matt Hart <email@hidden>)
 >Re: iOS 8 ExtAudioFile AppleLossless distortion (From: "Dave O'Neill" <email@hidden>)
 >Re: iOS 8 ExtAudioFile AppleLossless distortion (From: Robert Carroll <email@hidden>)

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