Re: Few sample rate conversion questions
Re: Few sample rate conversion questions
- Subject: Re: Few sample rate conversion questions
- From: work <email@hidden>
- Date: Sun, 04 Jan 2009 23:53:40 +1100
On Dec 24, 2008, at 7:30 PM, Mike Kluev wrote:
I have few interrelated questions about sample rate conversion.
1) The documentation states that AUVarispeed unit changes pitch as
well as speed:
<<A unit that lets you change the speed of playback (and
consequently the pitch as well)>>.
Yet, in the CAPlayThrough sample there is the following comment:
//Q:Why do we need a varispeed unit?
//A:If the input device and the output device are running at
different sample rates
//we will need to move the data coming to the graph slower/faster TO
AVOID A PITCH CHANGE.
Is this comment just not correct and it rather should be "to
introduce a pitch change"?
the differences in rate are minor and a varispeed is the correct unit
to use. If the rates are different, then you need to use a varispeed
to correct the slight difference in pitch that would otherwise occur.
Imagine that source a is running slightly slower than source b, then
if they are playing the same sound to a 3rd device, their pitches will
be slightly off - a varispeed corrects this.
2) Wouldn't it be better to use AUTimePitch instead of AUVarispeed
in this sample
and other code for similar purposes on the grounds that AUTimePitch
can change
the speed of playback without altering the pitch?
no - for this use the varispeed is the correct approach
3) For the purposes of sample rate conversion are AUConverter and
AUVarispeed
equally good? (Capable to handle the same set of input/output rates,
same quality, etc)
yes - they use the same underlying resampler
Bill
Mike
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden