• Status Closed
  • Percent Complete
  • Task Type Bugs
  • Category Codecs
  • Assigned To No-one
  • Operating System Sansa AMSv2
  • Severity Low
  • Priority Very Low
  • Reported Version Daily build (which?)
  • Due in Version Undecided
  • Due Date Undecided
  • Votes
  • Private
Attached to Project: Rockbox
Opened by markemark - 2012-04-28
Last edited by saratoga - 2012-05-01

FS#12655 - Low bitrate WMA becomes distorted on Sansa Clip Zip

When playing back certain low-bitrate WMAs with my Sansa Clip Zip, the audio becomes more and more distorted. The easiest way to show the problem in action is with a short low-bitrate WMA (20bps/22khz) I have attatched.

Set repeat to ‘one’ then playback the file and let it loop. Or press the forward button several times make the distortion happen faster. The audio will get more and more distorted every time the playback loop starts over until all I hear is distortion.

Using current build (04/28 version 8a3824f-120428).

Closed by  saratoga
2012-05-01 21:57
Reason for closing:  Fixed

Is this new? wondering if my recent wma fix broke something.

I don’t think so. The problem’s been around since I’ve bought my clip zip a few months ago. It was only recently I found a way to easily reproduce the problem of increasing distortion at every track change.

I’ll try and find time to look into this. Its probably something stupid like one of the variables not getting reset when playback loops verses when it starts a new track.

Ok I think I see the problem. During init, there a table of noise values which are doubled if the file use line spectral pairs (only for WMA files under about 20 kbps). Right now I think if the file is set to repeat, it doubles them each time, instead of just doing it once, so they gradually get more and more wrong as the file loops. Will have to figure out an efficient fix for this problem.

Should be fixed in 87d3dde.

Updated to current on my zip. Problem fixed here. Thank you much!


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