Re: Pitch-Shift on the iPhone
Re: Pitch-Shift on the iPhone
- Subject: Re: Pitch-Shift on the iPhone
- From: tahome izwah <email@hidden>
- Date: Fri, 6 Mar 2009 11:18:36 +0100
Hi Hamish, I think there is some confusion of terms in our discussion
- let me clarify:
You said: "You can change the pitch of something by timestretching it"
..which is wrong - time stretching changes the speed, not the pitch.
Which is why I replied saying:
"you change the pitch by pitch shifting"
That's all I wanted to point out in the context of your last email.
Time stretch + sample rate conversion = pitch shift
Pitch shift + sample rate conversion = time stretch
I think we all agree on this.
--th
2009/3/6 Hamish Allan <email@hidden>:
> On Fri, Mar 6, 2009 at 7:42 AM, tahome izwah <email@hidden> wrote:
>
>> 2009/3/5 Hamish Allan <email@hidden>:
>>
>>> You
>>> can change the pitch of something by timestretching it and adjusting
>>> the playback speed.
>>
>> Actually, you change the pitch by pitch shifting (not time stretching)
>> and then adjust the playback speed by sample rate conversion to
>> achieve time stretching.
>
> You might find it informative to read
> http://www.dspdimension.com/admin/time-pitch-overview/
>
> From the introduction:
>
> "As opposed to the process of pitch transposition achieved using a
> simple sample rate conversion, Pitch Shifting is a way to change the
> pitch of a signal without changing its length. In practical
> applications, this is usually achieved by changing the length of a
> sound using one of the below methods and then performing a sample rate
> conversion to change the pitch."
>
> Like I say, they're two sides of the same coin. If you can find a way
> to pitch shift, you can resample to time stretch. If you can find a
> way to time stretch, you can resample to pitch shift.
>
> You're quite right, though, that Andrew's answer is useless for the
> purpose of answering magno's question. I had assumed he had pointed
> him to some source code!
>
> Hamish
>
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