• Status Closed
  • Percent Complete
  • Task Type Bugs
  • Category Music playback
  • Assigned To No-one
  • Operating System Sansa AMSv2
  • Severity Low
  • Priority Very Low
  • Reported Version Release 3.7.1
  • Due in Version Undecided
  • Due Date Undecided
  • Votes
  • Private
Attached to Project: Rockbox
Opened by jdc - 2010-12-16
Last edited by bertrik - 2012-03-17

FS#11812 - Clip+ non zero output when paused

By measuring with a multimeter I found that when paused the clip+ outputs a constant DC voltage that will change with the volume. I believe it just outputs the sample it was on when it is paused rather than zero. It changes every time I pause it and is postive and negative. When I tried a file with just silence it was always zero when paused. The OF does not have this problem. This has a real potential to damage headphones if you have the volume up and were unlucky enough to pause on a peak.

Brief discussion on Head-Fi

Closed by  bertrik
2012-03-17 23:37
Reason for closing:  Fixed
Additional comments about closing:   Warning: Undefined array key "typography" in /home/rockbox/flyspray/plugins/dokuwiki/inc/parserutils.php on line 371 Warning: Undefined array key "camelcase" in /home/rockbox/flyspray/plugins/dokuwiki/inc/parserutils.php on line 407

Appears to be fixed now

We probably never noticed this because fade to pause is on by default in rockbox, and that should zero the output.

jdc commented on 2010-12-16 21:06

Thanks saratoga, never thought about that but I just checked and I don’t have it on. I just tested it and it doesn’t make a difference either way but I did find I get a squeak at pause and unpause with fade on but not with it off

jdc commented on 2010-12-16 21:06

I mean I do/did have it on.

I hear this too on my Fuze v2 with 3.7.1. When Fade on Stop/Pause is disabled the noise disappears.

Several people have noticed audible clicks on AMSv2 platforms when changing the volume while playback is paused. Perhaps these observations are an artifact of the present issue (nonzero voltage while paused)?

jdc, Could you please check whether the voltage you’ve been measuring changes when the volume is changed during pause?

jdc commented on 2011-03-06 21:25

Hi, sideral. yes it does

jdc commented on 2011-03-06 21:37

I should of added this reference too,26357.0.html

I took some measurements with the current build, and the DC level on pause or stop did not seem to be related to last sample on my Clip+ with current SVN. Instead, I got a small noise-like waveform that was related to the volume in amplitude (but only about 30mV at +6dB) but completely random as a function of time. After 2 seconds I could see a small pop as the DAC switched off. At that point the level dropped to within a few mV of 0 (the exact level also depended on volume).

Using high efficiency IEMs at +6dB I could confirm that my scope readings matched what happened with headphones: I hear a deafening music, then a faint hiss, then a pop as the output turns off. Finally I hear only a very faint hum which I assume is cross talk from the player’s CPU.

Edit: I should mention I made these measurements using a 1 megaOhm input impedance scope.

MikeS commented on 2011-07-25 05:51

PCM doesn’t really immediately stop on pause of the playback engine , but plays 3 seconds of silence after the last activity from some source before actually stopping it.

Since I can’t reproduce this, I think its fixed.


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