Apple

On Jan 31, 2013, at 11:26 AM, Tony Kirke <email@hidden> wrote:

I've also had the same issue based on Chris's demo project. In fact I just upgraded to 6.1 and am now getting silence instead of distortion. Were you on 6.0 or 6.1?

On Thu, Jan 31, 2013 at 3:27 AM, Jont Olof Lyttkens <email@hidden> wrote:

Hi!

I am building an app for iOS. which depends to a great extent on time-stretching and I was thrilled to find the NewTimePitch Audio Unit. I am configuring a simple AUGraph:

kAudioUnitSubType_AudioFilePlayer -> kAudioUnitSubType_NewTimePitch -> kAudioUnitSubType_RemoteIO

The parameter "rate" of the NewTimePitch is set from around 0.7 to 1.3. Problem is that the NewTimePitch Unit distorts the audio quite badly. I found this post on coreaudio-api-maillist which relates to the problem:

http://lists.apple.com/archives/coreaudio-api/2012/Sep/msg00020.html

Unfortunately I don't come to the same conclusion. I don't hear any phase problems, nor any monofication of the signal. We are only talking really bad distortion. I've done testing with all sorts of audio input down to a -24dB FS audio input and the distortion seems to be unrelated to volume.

Finally I found this blog post from CocoaConf by Chris Adamson, where he bundles the demo project from the conference:

http://www.subfurther.com/blog/2012/10/30/cocoaconf-portland-12-and-the-audioqueueprocessingtap/

I must admit that he pointed out a couple of things that I had missed out, but even after fixing these, I still had the distortion. More so, compiling the Demo Project from CocoaConf also distorted the audio, so I am beginning to wonder if the NewTimePitch AU really is corrupt.

A printout of my CAShow():

AudioUnitGraph 0xBD33001:
Member Nodes:
node 1: 'auou' 'rioc' 'appl', instance 0x815e940 O I

node 2: 'aufc' 'nutp' 'appl', instance 0xa85ade0 O I
node 3: 'augn' 'afpl' 'appl', instance 0x8298510 O I
Connections:

node 3 bus 0 => node 2 bus 0 [ 2 ch, 44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved]

node 2 bus 0 => node 1 bus 0 [ 2 ch, 44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved]

CurrentState:
mLastUpdateError=0, eventsToProcess=F, isRunning=F

I also have:

- Ensured that the StreamFormat of the AUNewTimePitch is set equally on all other units
- Setup the RemoteIO bus

Is there any magic trick that I need to know about or does anyone have a non-distorting sample of a graph that works with the NewTimePitch Audio Unit?

Best regards

/Jont Olof

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centCode AB

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References:
	>NewTimePitch Audio Unit Distorts Signal (From: Jont Olof Lyttkens <email@hidden>)
	>Re: NewTimePitch Audio Unit Distorts Signal (From: Tony Kirke <email@hidden>)
	>AudioQueueProcessingTap broken in 6.1? (was: Re: NewTimePitch Audio Unit Distorts Signal) (From: Chris Adamson <email@hidden>)