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: Steven Winston <email@hidden>
- Date: Wed, 9 Sep 2009 17:28:20 -0700
That's awesome! However, a question, is this solution going to suffer
from the same different files of the exact same format decode at
different rates problem? I'll start digging through 3.1 docs and will
eagerly await the further details.
On Wed, Sep 9, 2009 at 5:22 PM, William Stewart<email@hidden> wrote:
> 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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