Shockwave can be brought to a state where playing multiple sound channels at once crash

Hello all. Here's one nut too tough to chew on myself, so I
turn to you  
for help.

We have recently come across a most strange behavior in
shockwave. We do 
not have much clues yet as to what actually causes it, but
the scenario 
is this :

We are developing a MMOSG which has a two "sound
toys" / games. The 
other we have been running for more than a year now with no
problems, 
the other one we only recently released. The new one is
basically a 
conversion of the old one with different samples.

When developing the feature, at first we didn't notice
anything was 
wrong because the problem wouldn't appear in director at
all. After 
going to testing with protected .cct's downloaded over http
(on the 
browser shockwave plugin) we started to notice the problem:
The browser 
plugin would crash when trying to play 4 tracks of sounds at
once. But 
to make it stranger, the old "toy" kept working!
(Later we realized that 
if we put enough strain on the plugin the old one could also
be crashed, 
but you had to really slam it hard with updates sounds and
to what's 
playing on stage.)

To confuse us further, we play 4 tracks simultaneously most
of the time 
with no problems. We also have an editor for the sound toy,
which uses 
the same queue/playback mechanism, working without
crashing!

Now, it seems that somehow the plugin can be put to a state
in which 
playing the sample queues is just too much for it to handle.
Here's the 
code we use for queuing :

    t_track = 1
    repeat with t_channel in m_pSoundChannels
      sound(t_channel).setPlaylist([])
      repeat with e = 1 to m_iLastSample
        t_rmem = m_mp_TrackData[t_track][e]
        if t_rmem = 0 then t_rmem = t_rEmptymem             

        if t_rmem <> -1 then
sound(t_channel).queue(t_rmem)      
      end repeat
      t_track = t_track + 1
    end repeat

And here's what we use for playing :

      repeat with t_channel in m_pSoundChannels
        if objectP(sound(t_channel)) then
sound(t_channel).play()
      end repeat

Having seen the obviously simple code, you can propably see
that there's 
nothing obviously wrong with it. I'll explain what we did
find out :

We started looking for a pattern to reproduce the crash.
After a while 
we found one that we could reproduce in director as well.
Having a 
certain set of sprites active on the stage, with the 4
tracks started 
playing, we'd hit large sprite animations (which we
implement by 
manually setting the sprite members) and more sounds on the
remaining 
channels. When it crashed, we'd hit debug. Although the
debug window had 
insisted that "getProp()" was not a method of a
property list, the 
debugger's memory inspector did show the contents of the
list just 
fine.. We could even write the same exact statement that
crashed it in 
the watch list and it would resolve 

Only thing we did find out is that the crash didn't seem to
occur 
immediately on playback, but later in the frame when
updating one of the 
sprites in the before-mentioned animations. (Can we trust
the debugger 
on this? Is the call stack always correct?) The crash would
always be on 
the same supposedly missing "getProp()" of a large
property list where 
we hold sprite numbers for quick access.

The debugger didn't help us much there, so I finally tried
the "monkeys 
banging at a typewriter"-technique on it. I removed
code line-by-line 
and rearranged it around in all imaginable configurations.
Only thing 
that prevented the crash altogether was to remove playback
of 3 
channels. Now that's not good enough 

Sound familiar? Comments? Any help would be greatly
appreciated.

-toni aittoniemi / sulake corp.

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Shockwave can be brought to a state where playing multiple sound channels at once crash

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