Re: Changing mSampleRate for an Audio File
Re: Changing mSampleRate for an Audio File
- Subject: Re: Changing mSampleRate for an Audio File
- From: William Stewart <email@hidden>
- Date: Thu, 20 May 2004 13:03:19 -0700
On 20/05/2004, at 3:57 AM, Asher Vander Heiden wrote:
>
Hey Bob,
>
>
I've already tried what you suggest.
>
The problem is that I get errors when I try to fill the Destination
>
Audio Fiie with the data from the Source Audio File. Why? because they
>
are of different formats I'm guessing?
>
>
At the moment I'm using the 'auprocess' with the 'ReverseOfflineUnit'
>
and the same thing happens. When I try to use different
>
AudioStreamBasicDescription for the Destination Audio Fiie and Source
>
Audio File it fails to accept this.
That code was written only to do basically the same sample rate - so I
haven't tested this if you are trying to write a different format than
the source.
I think the only change that you'd have to make is that the file format
for the dest is what you want (ie. with the different sample rate), but
the ClientFormat for that dest file would be the same sample rate as
the source file (as you are going to be processing the audio at the
source file's sample rate I presume) - then the CAAudioFile would
include the sample rate converter for you
(You could do it the reverse way as well, where you read the source
file's data, but then have CAAudioFile do a rate conversion on it to
the destination format)....
CAAudioFile has essentially 2 formats - the file format and the client
format (the client format MUST be PCM, but the file format can be
anything legal)...
So, I think you just need to make sure you're setting these up properly
and it should work just fine.
>
>
This is why I needed to change the mSampleRate of the Destination
>
Audio Fiie AFTER I have created the file and completed all the signal
>
processing.
Not quite - you'd rate convert the data before it gets written to the
file by setting the client data and dest file formats up correctly
HTH
Bill
>
>
Thanks for your answer,
>
>
Asher
>
>
>
> From: Bob Aron <email@hidden>
>
> To: Asher Vander Heiden <email@hidden>
>
> Subject: Re: Changing mSampleRate for an Audio File
>
> Date: Wed, 19 May 2004 09:21:40 -0700
>
>
>
> It sounds like you are not setting the AudioStreamBasicDescription
>
> correctly when you create the new audio file. Are you using
>
> AudioFileCreate() and passing it the ASBD describing your newly
>
> formatted data? What format is the data that you are converting from
>
> and to?
>
>
>
> bob aron
>
> ____________________________________________
>
> CoreAudio Team
>
> Apple Computer Inc.
>
> (408) 974-1221
>
> email@hidden
>
>
>
> On May 19, 2004, at 3:46 AM, Asher Vander Heiden wrote:
>
>
>
>> Hello,
>
>>
>
>> Is it possible to change the 'sample rate' of an AudioFile, without
>
>> using the Audio Converter?
>
>>
>
>> The reason for this is that I have been working on my own Sample
>
>> Rate Converter, which works on manipulating the Audio Stream of an
>
>> existing Audio File and saving the stream into a New file. So
>
>> therefore the New file that has been created has samples in the new
>
>> sample rate, while the AudioStreamBasicDescription, of the New file,
>
>> displays the old sample rate.
>
>>
>
>> I'm finding it really difficult to manually change the value of
>
>> mSampleRate within the New files AudioStreamBasicDescription. Even
>
>> if I could do this I'm not quite sure that this is the only value
>
>> that needs to be changed within AudioStreamBasicDescription.
>
>>
>
>> I would appreciate it if someone could tell me how this could be
>
>> done.......
>
>> I'm beginning to think that maybe it can't....
>
>>
>
>> Please Help ....
>
>>
>
>> Asher Vander Heiden
>
>>
>
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