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Subject: Plating silence, revisited.
From: Michael O'Quinn (michael_at_oquinn.info)
Date: 2003-03-29


~Hi All,

I've been following the development of RockBox for the last month or so,
since about 1 day after I got my Player 10 and discovered how little I
liked the original firmware...

Anyway, one ongoing theme seems to be "playing silence,", which (if I am
reading this right) most folks believe has to do with faulty disk reads
resulting in a lot of zeros being "played."

My version is Player CVS-030326.

I was playing a 256 CBR song, and encountered the Silent Play Feature
(tm), so I decided to see if I could reproduce it and observe anything
that might be useful.

It turns out I can reproduce it on demand, every time with any song on
that album. (They are all 256 CBR.) Here's how. I jump to the beginning
of the song, and then while this disk light is still on (actually might
work if I wait a bit, didn't test that) if I immediately FF to between 0:52
and 0:58 in the song, the red light comes on, and it plays silence, but
the seconds keep counting up.

After a random time, between 1:22 and up to the next buffer refill, the
music starts again, but usually WITHOUT reading the disk. No spin up
vibration, no red light, the music just restarts by itself. A couple of
times it went until somewhere around 2 minutes into the song, and the
music restarted after a disk spin up and read.

Time to FF doesn't seem to affect it. At first my FF was set at min step
= 2 sec, and accel = 2x/1 sec. I eventually ramped that down as slow as
possible (min step = 1 sec, accel = off) to get more accurate, and it
didn't seem to affect it. (Except, of course, that the behavior got more
consistent as my seeks got more accurate...)

One thing that affected this is that most times when I would jump to the
beginning of a song, it would start counting up and playing from 0:00.
Sometimes, however, there would be a pause, and it would start counting
and playing from between 2-5 seconds into the song. (This is actually a
minor bug in itself -- beginning of the song shouldn't be chopped off like
that.)

The Silent Play Feature (tm) would only activate when the song started
playing from 0:00, and NEVER when it started a few seconds into the song.

What seems significant about this is that, in terms of reads and filling
buffers, it seems that the BEGINNING of the buffer that's getting munged,
not the END.

This isn't a cry for help. I'm very satisfied (thrilled actually!!!) with
RockBox, to the point that I forget the actual device is a "Jukebox", not
a "RockBox". Rather, I've been looking for a way to get involved and
help, and I figure a decent bug report is one way to get started. I could
provide one of the songs, or do more testing if someone wants..

I hope this helps in tracking this one down.

Michael O'Quinn



Page was last modified "Jan 10 2012" The Rockbox Crew
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