Re: AU/HAL buffer alignment
Re: AU/HAL buffer alignment
- Subject: Re: AU/HAL buffer alignment
- From: Kurt Bigler <email@hidden>
- Date: Mon, 10 Mar 2003 13:14:35 -0800
on 3/10/03 12:27 PM, Chris Rogers <email@hidden> wrote:
>
Actually, just to clarify. malloc() does return addresses which are always
>
altivec (16byte) aligned. Something which we probably have not documented
>
properly, but which is very important for AudioUnits is that buffers
>
passed around in AudioBufferLists should ALWAYS be altivec aligned.
>
AudioUnits are supposed to be able to assume this alignment when doing
>
their internal DSP...
Thanks, that's great.
Everyone please ignore my last message a couple minutes back which crossed
with Chris's in the mail.
-Kurt Bigler
>
>
Chris Rogers
>
Core Audio
>
Apple Computer
>
>
>
>
> The HAL doesn't make any guarantees about the alignment of the
>
> buffers. I don't think that Audio Units make any guarantees about
>
> the alignment of the buffers either.
>
>
>
> The HAL uses malloc to allocate it's buffers. The default behavior
>
> of malloc is to allocate chunks a page or larger in size so as to be
>
> page aligned. Chunks smaller than a page don't have any guarantees
>
> about alignment.
>
>
>
> On Saturday, March 8, 2003, at 11:05 PM, Kurt Bigler wrote:
>
>
>
>> All the buffers passed by an output AU to my render callback appear
>
>> to be VERY aligned - like on a 4K boundary. Is this something we
>
>> can count on for buffers passed from both output AUs and the HAL?
>
>>
>
>> The real question is whether we can count on 128-bit alignment, to
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>> simplify AltiVec development.
>
>>
>
>> Thanks,
>
>> Kurt Bigler
>
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>
>
> --
>
>
>
> Jeff Moore
>
> Core Audio
>
> Apple
>
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