Re: AudioConverter strategic decision
Re: AudioConverter strategic decision
- Subject: Re: AudioConverter strategic decision
- From: William Stewart <email@hidden>
- Date: Mon, 27 Sep 2004 10:55:00 -0700
On 25/9/04 11:07 AM, "Marc Van Olmen" <email@hidden> wrote:
> hi,
>
> I have some old code that I want to modernize with coreAudio.
>
> I noticed that CoreAudio has an AudioConverter API, I current am using
> the SoundManager SoundConverter API.
>
> I mainly playback tracks from QuickTime Movies, to be more specific DV,
> DVPro and AAC.
>
> Going quickly through the documentation and sample code.
>
> It looks very similar to my current VBR safe Soundconverter code. But
> there is some new initalization setup etc... So I'm thinking of doing
> the switch in the next couple weeks.
>
> But first I have some questions:
>
> 1. Is the AudioConverter thread safe? I know that Sound Converter is
> not.
No - deliberately not... If you are using it from multiple threads, then
call it in a thread-safe manner.
>
> 1b. Can i for example use Semaphores to sleep the GetDataProc callback
> when no data is available?
With the AC you just return an error and no data when you have no data
available... You may get called a few times (just keep returning)... Then
your ACFillCompexBuffer call will return = and you put that to sleep.. When
you have more data, just call it again and it will continue from where you
left off.
>
> 2. I'm aware that audioconverter doesn't implement all codecs, I don't
> think that it does DV natively?
Correct. DV is not a codec, it is a way to layout PCM data in a container.
Quite a difference.
>
> 3. I read somewhere that the AudioConverter API will rely on the
> SoundConverter API in case it can't find a native coreAudio codec. Does
> that keeps my code thread safe??
See (1)
>
> 4. Is there any code to convert any SoundManager Atom's to
> MagicCookies? I saw one sample for MPEG4-AAC
Not at this stage - we are adding some properties to generically convert
between ESDS and the CA Structures.
>
> 5. Is there anywhere some sample code that plays any QT movie Audio
> track using the AudioConverter API.
There's some basic code to get you started in the CA SDK - take a look in
the AudioFileTools directory.
Bill
>
> thx for your time,
>
> mvo
>
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