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FS#12697 - SanDisk Sansa Clip+ 48000Hz rec 2.35% fast, but 44100Hz rec is fine

Attached to Project: Rockbox
Opened by Gordon McDowell (gordonmcdowell) - Wednesday, 13 June 2012, 22:09 GMT+2
Last edited by MichaelGiacomelli (saratoga) - Wednesday, 13 June 2012, 22:56 GMT+2
Task Type Bugs
Category Recording
Status Unconfirmed
Assigned To No-one
Player Type Sansa AMSv2
Severity Low
Priority Normal
Reported Version Release 3.11
Due in Version Undecided
Due Date Undecided
Percent Complete 0%
Private No

Details

Player Type = Sansa Clip+ (not available in chooser when submitting).
Release = 3.11.2

Recording at 48kHz results in audio that is 2.35% too fast. I believe it is recording at 49155Hz instead of 48000Hz. Recording at 44.1 kHz does not have this problem.

I have verified by putting 2 identical Clip+ in front of me, one set to rec at 44.1 other at 48.0. When playing back audio (on PC) difference in pitch is (barely) audible. And the audio falls out of sync as recording progresses (in video editor).

For now I'll be happy to only record at 44.1kHz, but maybe 48kHz recording should either be fixed or dropped from Clip+ options.
This task depends upon

Comment by Gordon McDowell (gordonmcdowell) - Wednesday, 13 June 2012, 22:14 GMT+2
Or maybe it is recording at 46872Hz. That's my new guess.
Comment by Michael Sevakis (MikeS) - Thursday, 14 June 2012, 00:07 GMT+2
None of them will be perfect.; these devices aren't that accurate. If a difference in pitch is actually audible if directly comparing when switching with the test_samplerate plugin, I would say drop any such rate. Alot of the rates are very far off on AMS. I've never included any such rates in my own code just to have an impressive list that's in the hardware range.

ETA:
I guess that would include 12000 and 24000.

Another option, if it would help, would be to slightly adjust the PLL frequency on the fly to get close enough the target frequency.

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