Re: AUVarispeed usage question
Re: AUVarispeed usage question
- Subject: Re: AUVarispeed usage question
- From: "Kevin Dixon" <email@hidden>
- Date: Tue, 22 Apr 2008 17:30:32 -0400 (EDT)
- Importance: Normal
This isn't exactly what I had in mind. I need to process a file, with
constantly changing PlaybackRate (I *want* the pitch to change) but still
output a 48kHz or 44.1kHz file in the end, as specified by the user.
Does this mean I have to calculate my desired output sample rate and
change the output stream format for each slice?!
Is this application not appropriate for the AUVarispeed?
-Kevin
> Kevin,
>
> I think the unit respects the input and output formats that you give
> it. Meaning, if the input AudioStreamBasicDescription == output
> AudioStreamBasicDescription then you are always going to get the same
> sample rate on both ends.
>
> If you checkout the CAPlayThrough example, the CAPlayThrough.cpp file
> has 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.
>
> If you read through the CAPlayThrough::SetupBuffers method, you'll
> notice that the varispeed unit's input is set to the format of the
> AUHAL's nominal sample rate and the output format is set to the
> default output's nominal sample rate.
>
> Hope that helps!
> Peter
>
> On Apr 22, 2008, at 1:45 PM, Kevin Dixon wrote:
>
>> I still haven't gotten a response from my previous post, so I'm
>> going to
>> rephrase my question.
>>
>> If I'm using the AUVarispeed, and have playback rate != 1 or pitch
>> change
>> != 0, then I should expect to get a different amount of samples out
>> than I
>> put in, correct?
>>
>> So far I have been getting the same amount in and out. I was
>> wondering if
>> there's some property I should check to see what samples to actually
>> use,
>> or something of the sort. Thanks in advance,
>>
>> -Kevin
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