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: 水鳥 敬満 <email@hidden>
- Date: Sat, 09 Jan 2010 00:24:33 +0900
Hi Doug
Thank you for your comment.
I'll write a bug report, and post buildable example after I remove some unnecessary and shameful part of code from my current snapshot.
Br.
Taka
On 2010/01/08, at 7:37, Doug Wyatt wrote:
> 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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