Speed problems with imported .m4a files

[Fred Kells]

Occasionally, an .m4a file imported into Cakewalk plays around 10% slower than it should - enough that it begins drifting out of sync with the other tracks after a few seconds.

-- The pitch is normal.

-- The sample rate is correct.

-- The same problem happens when that file is imported into other audio software (i.e., it's not a Cakewalk issue).

-- So far, when I ask the sender to re-record, the second file is fine.

Any idea what causes this?  And how to avoid it?

Thanks, guys!

     Fred

[bitflipper]

It's obviously file corruption. I don't know why m4a files are particularly prone to corruption, only that every software player that supports them offers a utility for repairing corrupt m4a files, suggesting that it  might be a common occurrence.

I can imagine that if a few of the data blocks somehow went MIA in transit the resulting gaps might be brief enough to not actually be audible, but the data would be out of sync. If those gaps were scattered throughout the file, the desynchronization would gradually get worse until the cumulative error became great enough to hear.

Were these files created by someone with a DAW, or were they originally iTunes downloads? If the former, you could ask the sender to use a different file format. If the latter, then the files were likely corrupted during their initial download. However, I believe iTunes does offer a repair tool, as well as the ability to convert them to MP3. 

Another thought...the files could have been corrupted when the sender sent them to you. Were they sent as MIME-encoded email attachments by any chance? 

[Fred Kells]

The files are vocal recordings on  Apple phones or tablets.  Many of my clients use Apple products, but I've only had this problem with two of them.

The latest file came as an email attachment (Gmail).  The email itself is MIME-encoded (Ver. 1.0).  Does that mean the attachment is also encoded? If so, is there a way around this, or must the sender use something other than email to get the file to me?

Many thanks!