Re: Accessing audio samples from Audio Queue Buffers
Re: Accessing audio samples from Audio Queue Buffers
- Subject: Re: Accessing audio samples from Audio Queue Buffers
- From: William Stewart <email@hidden>
- Date: Wed, 9 Sep 2009 17:22:46 -0700
One of the new things in iPhone OS 3.1 is that you can use
ExtAudioFile to read and write compressed data where you may need to
use a hardware assisted codec (such as AAC encoding) to do so.
Details are forthcoming, including some example code - have a look in
the tech notes and release notes for the 3.1 release
Bill
On Sep 9, 2009, at 3:54 PM, Steven Winston wrote:
Does this work? I haven't tried it, but I heard that ExtAudioFile
wouldn't work correctly for iPhone in this regard which is why there's
a tech Q/A about how to do offline rendering.
On Wed, Sep 9, 2009 at 3:29 PM, Jean-Daniel Dupas<email@hidden
> wrote:
I Never dev for iPhone but isn't it possible to simply uncompress
the data
using the ExtAudioFile API ?
http://developer.apple.com/iphone/library/documentation/MusicAudio/Reference/ExtendedAudioFileServicesReference/Reference/reference.html
Le 10 sept. 2009 à 00:11, Steven Winston a écrit :
Howdy KappA,
The best solution I've found is to use AudioQueueOfflineRender. The
only problem with it, is it's next to impossible to, for me at
least,
get the timing right between the various formats that AudioQueue
supports. See you have to have one AudioQueue to do an offline
render, then change the PCM you receive in the buffer, then send
that
back out all while staying ahead of the file being played. My
problem
comes from the fact that some files & formats play at different
speeds
through the offline render than others.
The only other solution I have come up with that solves this problem
is to port a MP3Library / OggLibrary and do things entirely in
software. It's not as fast as there's no benefit from the hardware
for speed, but at least the rate of decompressing is uniform.
Ofcourse there's probably a trick I'm missing here.
Thanks,
Steve
On Wed, Sep 9, 2009 at 1:48 PM, KappA<email@hidden> wrote:
Hi All,
I am hoping this is a somewhat simple question. I am using Audio
Queue's
for
audio playback (iPhone OS3), and I would like to add some simple EQ
effects
to the audio output... I am supporting MP3 and AAC playback, so I
will
need
my solution to still be able to support these formats.
I'd basically like to use this EQ function:
http://musicdsp.org/archive.php?classid=3#236
Which takes an audio sample input of type "double", and returns a
modified
sample output, of type "double"
I can actually see where we copy the audio bytes to the audio
buffer data
structure, in the Audio Queue Services callbacks... but I am not
sure how
to
convert the raw audio bytes to audio samples, where I can
manipulate
them...
Is this even possible? Am totally off base here?
If it is not possible, any other ideas to acheive something
similar with
Audio Queues?
If I cannot do it with Audio Queues, is there something else I
can use
for
playback, that will support MP3's and AAC etc?
I can share more info if needed.
Any help appreciated.
Thanks,
KappA
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-- Jean-Daniel
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