I'm personally using mp3 but uncompressed formats are perfectly fine provided you set the asbd correctly.
AudioStreamBasicDescription destinationformat={0};
destinationformat.mSampleRate=DEFAULT_SAMPLE_RATE;
destinationformat.mFormatID =kAudioFormatLinearPCM;
destinationformat.mFormatFlags=kAudioFormatFlagsNativeEndian|kAudioFormatFlagIsSignedInteger|kAudioFormatFlagIsPacked;
destinationformat.mBytesPerPacket=4;
destinationformat.mFramesPerPacket=1;
destinationformat.mBytesPerFrame=4;
destinationformat.mChannelsPerFrame=2;
destinationformat.mBitsPerChannel=16;
On 8 May 2012 13:40, Morgan Packard
<email@hidden> wrote:
Thanks for the anecdote Barry. Exactly the sort of info I was looking for. Can you confirm that you're using uncompressed files?
-Morgan
On Tue, May 8, 2012 at 4:20 AM, Barry Duggan
<email@hidden> wrote:
Have you considered using several aufileplayer units (ios 5) and a mixer unit?
I'm successfully mixing 20 stereo files at the moment with no performance issues.
Also, if you can't use ios 5 for what ever reason you could ExtAudioFileRead to read frm disk into memory in chunks like you do now. Again I've been able to read a lot of files from disks this way without any performance issues.
Prehaps you're incurring some overheads from using non apple libraries for whatever reason ?
On 7 May 2012 20:00,
<email@hidden> wrote:
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Today's Topics:
1. About how many channels of 16/44.1 PCM audio should I be able
to stream from disk on an iPhone 4? (Morgan Packard)
----------------------------------------------------------------------
Message: 1
Date: Sun, 06 May 2012 17:09:19 -0400
From: Morgan Packard <email@hidden>
To: email@hidden
Subject: About how many channels of 16/44.1 PCM audio should I be able
to stream from disk on an iPhone 4?
Message-ID:
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Content-Type: text/plain; charset="iso-8859-1"
Most of my audio code is built on top of the
STK<https://ccrma.stanford.edu/software/stk/> library.
I'm using STK's FileRead class to load audio from disk (which in turn uses
fopen to read the files).
I want to be able to play long files (too long to fit in memory), so I'm
loading them a bit at a time from disk before mixing them and sending them
out via the remoteIO callback.
The code I'm currently running is pretty solid streaming three stereo files
from disk, but begins to get glitchy as I start to add files above that.
I'd be grateful for a rough ballpark of how many stereo files I should be
able to play back simultaneously.
Questions:
- Am I indeed going to be limited by disk speed to a fairly low number of
files?
- Is disc speed enough of a bottleneck so that using compressed files might
give me a higher number of parallel playbacks?
- Is there something inherently slow or unreliable or inappropriate for
streaming audio from disk about fopen?
thanks,
-Morgan
--
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Morgan Packard
cell: (720) 891-0122
aim: mpackardatwork
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