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Re: Issues in ExtAudioFileSeek and ExtAudioFileTell

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Re: Issues in ExtAudioFileSeek and ExtAudioFileTell

Subject: Re: Issues in ExtAudioFileSeek and ExtAudioFileTell
From: Doug Wyatt <email@hidden>
Date: Fri, 6 Nov 2009 13:38:24 -0800

Actually, I think I see the problem. If you seek to an offset within the same packet as the current read mark, we bypass some logic that looks important, and for a pretty dubious reason (trying to avoid unnecessarily resetting the converter).

Our sparse documentation for these functions seems to be leading you in the wrong direction too. The offsets passed to Seek and returned by Tell are relative to the priming offset. So if you seek to offset 0 and start reading in a file with 2112 frames of priming, that will return samples starting at offset 64 of the third packet (1024 + 1024 + 64 = 2112).

Doug


On Nov 6, 2009, at 10:35 , Doug Wyatt wrote:

What version of what OS are you running?

What other calls to ExtAudioFile are you making before the first calls to ExtAudioFileSeek and ExtAudioFileTell?

What are the sample rates of the file and the client format (if any)?

Doug

On Nov 5, 2009, at 23:16 , Abdul.Majeed wrote:

Hi Bill,
  Thanks a tone for your quick response.
   Please here it is more information

  1. for another .mp3 file result i got as


Sint64 theOffset = (primeOffset + 0); //it gives 576
ExtAudioFileSeek(fileRef,theOffset);
ExtAudioFileTell(fileRef,&theOffset);   ///  theOffset gives 0

//read a sample frame of theNumPackets =  4096
ExtAudioFileRead(filRef,& theNumPackets,&BufferList);

ExtAudioFileTell(fileRef,&theOffset);   /// theOffset gives 4672

  2. for another .m4a file result i got as

Sint64 theOffset = (primeOffset + 0); //it gives 2112
ExtAudioFileSeek(fileRef,theOffset);
ExtAudioFileTell(fileRef,&theOffset);   ///  theOffset gives 0

//read a sample frame of theNumPackets =  262144
ExtAudioFileRead(filRef,& theNumPackets,&BufferList);

ExtAudioFileTell(fileRef,&theOffset);   /// theOffset gives 264320

 3. for another .m4v file result i got as

Sint64 theOffset = (primeOffset + 0); //it gives 2112
ExtAudioFileSeek(fileRef,theOffset);
ExtAudioFileTell(fileRef,&theOffset);   ///  theOffset gives 0

//read a sample frame of theNumPackets =  262144
ExtAudioFileRead(filRef,& theNumPackets,&BufferList);

ExtAudioFileTell(fileRef,&theOffset);   /// theOffset gives 264320

so in conclusion, if there primeOffset value from kAudioConverterPrimeInfo is greater than 0 then only this issues coming else it is fine. Could you please help me by giving your valuable inputs.

Thanks for your time.
abdul


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Re: Issues in ExtAudioFileSeek and ExtAudioFileTell
From: Abdul.Majeed <email@hidden>


References:  
  >Issues in ExtAudioFileSeek and ExtAudioFileTell (From: "Abdul.Majeed" <email@hidden>)
  >Re: Issues in ExtAudioFileSeek and ExtAudioFileTell (From: William Stewart <email@hidden>)
  >Re: Issues in ExtAudioFileSeek and ExtAudioFileTell (From: Abdul.Majeed <email@hidden>)
  >Re: Issues in ExtAudioFileSeek and ExtAudioFileTell (From: Doug Wyatt <email@hidden>)




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