Re: Audio glitches during playback thru Remote IO unit (iPhone)
Re: Audio glitches during playback thru Remote IO unit (iPhone)
- Subject: Re: Audio glitches during playback thru Remote IO unit (iPhone)
- From: Steven Winston <email@hidden>
- Date: Wed, 12 Aug 2009 10:36:05 -0700
The trick with RemoteIO's render function is to remember that timing
is everything. You MUST keep the buffer full and read ahead of when
you need it. You can change the rate at which the render function is
called, but in general plan for every 40ms having enough data to fill
the buffer. To avoid glitches, the render function should do nothing
more than memcpy out the buffer you want. Avoid doing any processing
in the render function like the plague. I saw an example RemoteIO
implementation that reads and plays a wav file. I think it's here:
http://sites.google.com/site/iphonecoreaudiodevelopment/home
best of luck!
Steve
On Wed, Aug 12, 2009 at 7:59 AM, Zhiye (Sterling)
Li<email@hidden> wrote:
> Hi Tahome,
>
> Thanks for your reply. I made a NSThread method where I use the
> AudioFileReadPackets() to read data to a double buffered queue, and now in
> the playback callback function it only calls the thread method when the
> buffer needs to be updated.
>
> It's my thread method:
>
> // File Reader thread
> -(void)readData {
>
> NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
>
> // Double buffer stuff.
>
> // Read file.
> AudioFileReadPackets ( )
>
> [pool release];
> }
>
> However, it didn't sound much better. I've also changed the thread priority
> number for both the render thread and the file reader thread that I made, it
> happened that the results were a little bit different, but it's just the
> matter of more glitches or less. So maybe there is a better way to do the
> file reader thread? Do you or anyone have any reader thread example that I
> can learn from?
>
> Thanks!
>
> Zhiye
>
>
>
>
>
>
>
> On Wed, Aug 12, 2009 at 2:02 AM, tahome izwah <email@hidden> wrote:
>>
>> I think it is discouraged to do synchronous reads within a render
>> callback. You should have a separate reader thread and queue up your
>> audio buffers in memory until they are needed for playback.
>>
>> --th
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