Re: ExtAudioFileSeek doesn't seek properly in m4a file
Re: ExtAudioFileSeek doesn't seek properly in m4a file
- Subject: Re: ExtAudioFileSeek doesn't seek properly in m4a file
- From: Doug Wyatt <email@hidden>
- Date: Thu, 7 Jan 2010 14:37:20 -0800
Unfortunately I think the trailing frames info for .m4a files is not being adjusted to compensate for the difference between the file and client sample rates.
Please write a bug report: http://bugreport.apple.com
If you have a fully buildable example that demonstrates the problem that would help, thanks.
Doug
On Jan 7, 2010, at 5:01 , 水鳥 敬満 wrote:
> Hi
>
> While I'm seeking m4a file with ExtAudioFileSeek, I found strange behavior.
> I seek m4a file of 44.1kHz sample rate and I set the sample rate of client format 22.05kHz.
> According to Ext Audio Service reference, I should give the frame index of "original file data format" to
> ExtAudioFileSeek, so I multiply 2 to client frame index since client data sample rate is half of the 44.1kHz.
> So code looks like below.
>
> ExtAudioFileSeek(xafref, 2 * clientFrameIndex)
>
> This works perfectly on mp3 file, I can seek to exact position I want and following ExtAudioFileRead load audio data from the position I seeked.
> But when I do the same things on m4a file, subsequent ExtAudioFileRead works only until the half of the audio file.
> If I seeked beyond the half of the audio file length, ExtAudioFileRead doesn't load any frames.
> Since this frame index (i.e. the half of the file) is the end of the file in client data format (since sample rate is half), I guess something is misunderstood inside ExtAudioFileSeek or ExtAudioFileRead.
> (When I try to set client data format's frame index (i.e. doesn't multiply 2) in ExtAudioFileSeek, the seeked position is not correct.)
>
> Does any have similar experience ?
> I really appreciate any advice on this topic.
>
> Best regards.
> Taka
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