Re: Audio data in float format for iOS?
Re: Audio data in float format for iOS?
- Subject: Re: Audio data in float format for iOS?
- From: tahome izwah <email@hidden>
- Date: Tue, 18 Jan 2011 07:07:51 +0100
No. We convert on input (and output) and stay entirely in float32 land
for all computations.
--th
2011/1/17 Gregory Wieber <email@hidden>:
> Does your code go back and forth between integers and floats? (Typecasting /
> converting?).
> Curious, because if your observations are accurate, than it implies the
> documentation is incorrect on this matter...
>
>
>
> On Mon, Jan 17, 2011 at 12:58 PM, tahome izwah <email@hidden>
> wrote:
>>
>> I don't think that this is true, especially for large chunks of fp
>> code. Our stuff definitely runs faster with thumb off, for both ARM 6
>> and 7 targets.
>>
>> --th
>>
>> 2011/1/17 Gregory Wieber <email@hidden>:
>> > Again, this is NOT true for arm7 (in which case it is recommended to
>> > leave
>> > thumb ON)
>> > On Mon, Jan 17, 2011 at 12:41 PM, tahome izwah <email@hidden>
>> > wrote:
>> >>
>> >> Float is usually slow when you're compiling for the thumb instruction
>> >> set. To see a real speed gain make sure you turn thumb off in Xcode
>> >> settings when you're doing a lot of fp calculations.
>> >>
>> >> --th
>> >>
>> >> 2011/1/17 Gregory Wieber <email@hidden>:
>> >> > Morgan,
>> >> > Depending on the processor you are using, you may be taking a HUGE
>> >> > hit
>> >> > for
>> >> > those conversions between integers and floats. I noticed a giant
>> >> > speed-up
>> >> > in my app when I removed any floating point operations and converted
>> >> > everything to integer calculations (which means you'll most likely
>> >> > have
>> >> > to
>> >> > read up on bit shifting, etc).
>> >> > Again, as I just mentioned though, this was for an app compiled
>> >> > without
>> >> > Thumb enabled. On newer processors, thumb 2 supports floating point
>> >> > calculations, so I would also be curious to hear other's
>> >> > recommendations.
>> >> > Specifically, to your question: from my limited knowledge on the
>> >> > subject,
>> >> > whether you use integers or floats really depends on the processor.
>> >> > I
>> >> > would
>> >> > look at whether your app needs to work on older devices where thumb
>> >> > is
>> >> > not
>> >> > recommended, and if so, avoid floats. Otherwise, let's see what some
>> >> > of
>> >> > the
>> >> > more experienced folks here recommend for the newer processors that
>> >> > support
>> >> > floats with thumb 2.
>> >
>> >
>
>
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