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  #1  
Old 2005-01-03, 10:22 AM
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Weird playback problem

Right, my ongoing inability to concentrate on journals about management accounting, the environment and sustainability has lead me to finally bother typing this out in the hope that some of you fine people can help.

The problem, simplified: stereo playback periodically switches to mono for no discernable reason.

The problem, expanded: this mono playback sounds as though it's like the "central channel" - stuff that is wide left or right disappears, and what plays is what is found near-equally in both channels. However, it's hard to be sure if this perception is correct. At one point I decided that it was just the left channel moving over but then I changed my mind. There is volume loss, but that makes sense, and there may also be some frequency-range loss, but I can't be sure - could just be because particular frequencies are split widely and so vanish.

My system (ahem, blush, etc): eMachines desktop, WinXP Home, year and a half old, 2.3GHz Intel Celeron processor, 256MB RAM, 80GB sensibly defragmented hard drive typically half-to-two-thirds full, Genius PCI soundcard (cheap yes, but very low noise analogue input).

I am aware that the soundcard's drivers are not fully suited to XP, but am fairly confident that this is not the problem as per the following and as per the fact that it's often perfectly functional. Anyway, in no particular order, the following paramaters apply:
  • The problem occurs with all relevant media filetypes - flac, shn, wave, mp3 - though with slightly different results (see below).
  • I have experienced the problem using all relevant playback software (foobar, Winamp, Goldwave, CDWave etc) EXCEPT Windows Media Player (though obviously I haven't been able to test shn/flac in WMP).
  • It occurs when playing media off all relevant hardware - hard drive, audio CDs, data DVDs. My Samsung SM-348B CDRW/DVD drive is a lot more prone to the problem than my Pioneer DVR-106D DVDRW drive or my hard drive.
  • I've been unable to specify the cause as either CPU-intensive or hard-drive use intensive, as it is possible to be working these hard without troubling playback. A sure fire way to induce a major burst of the problem is to extract an audio CD - during extraction, any currently playing media file will jump to mono and back frequently and rapidly.
  • With lossless/wave files, it tends to be that playback jumps to mono for a bit and then re-adjusts itself after a few seconds, but prolonged spells and/or quick flutters are also possible. With mp3 playback in foobar, if a file ends up in mono, it'll stick there until you reload/restart playing it.
The only possible lead I have thought of but not investigated is that it is a RAM-based problem. I know a link to a monitoring utility was posted the other day, so I'll look into that when I get chance, but as I say, I've been thinking about typing this for ages and I finally got bored enough of academia. If there's any other info I've missed I'll add it into the mix when I remember it.

Thanks in advance for any hints!
Rob
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  #2  
Old 2005-01-03, 10:39 AM
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Re: Weird playback problem

okay, this is really weird!! I'll post the couple of things that came to mind when I was reading this, but upon finishing reading I'm not so sure if they'll help.

-check your soundcard settings. sometimes there's a "3-d" option or something of the sort in the advanced options, turn make sure that's off.

-perhaps one of your speakers is wired out of phase? try reversing the red and black wires of either the left or right speaker if possible.

-try another soundcard, you can get the bottom of the line soundblaster for $20 here, small price to pay for the information you might get from the experience.

-as you mentioned, try this: http://www.jfitz.com/software/RAMpage/

hope this helps
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  #3  
Old 2005-01-05, 01:53 PM
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Re: Weird playback problem

- if you haven't done so already, try different output methods (like waveOut, DirectSound, Kernel Streaming etc in foobar)
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  #4  
Old 2005-01-10, 05:11 AM
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Re: Weird playback problem

OK gonna drag this back up as I spent a bit of time playing around this morning:

All the 3D etc advanced options are off.

It's definitely not a physical output / wiring problem because it's definitely occuring before that stage as if I set up recording software to record soundcard output, playback problems are recorded - gonna sort out some samples later as I had a slight twist on the problem this morning.

Had a quick look at the RAM monitor and I have at least half my RAM and PF free, and nearly all of my VM free, so I don't think it's that. And whether the problem occurred or not was independant of the current RAM level.

Tried switching from wave out to direct sound and the first thing I played back was a big chunk of mono so that's not the problem either.

This of course leaves the option of another soundcard, which is actually quite sensible, as long as I'm correct in thinking you can run two soundcards at once yes? I'd want to keep this Genius one for line-in recording because of the low noise floor, then use something else for general playback. The hifi I playback through has two line-ins, so I could connect both soundcards to it and it wouldn't be a problem when I want to directly listen to what I'm line-recording.

Thanks for all the feedback so far anyway - shame I've had to dismiss most of it!
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  #5  
Old 2005-01-10, 05:20 AM
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Re: Weird playback problem

Yeah, you can have two soundcards. I have four in my main comp

the whole mono-stereo thing I still can't figure out, tho.
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  #6  
Old 2005-01-10, 05:43 AM
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Re: Weird playback problem

Quote:
Originally Posted by Five
Yeah, you can have two soundcards. I have four in my main comp
the whole mono-stereo thing I still can't figure out, tho.
Cool. I forgot to note the slight variation I've discovered today in my post above. I suffered the frequency range losses while retaining (I think all of) the stereo split. Also, I just realised, the big fat chunk of mono I noted above was definitely left-channel only - not convinced that this is typical, but it's definitely what happens sometimes.
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  #7  
Old 2005-01-10, 05:55 AM
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Re: Weird playback problem

and I forgot to mention in any posts that the problem is much worse if the computer has come back from being on standby
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  #8  
Old 2005-01-10, 06:02 AM
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Re: Weird playback problem

Quote:
Originally Posted by robkismet
Cool. I forgot to note the slight variation I've discovered today in my post above. I suffered the frequency range losses while retaining (I think all of) the stereo split. Also, I just realised, the big fat chunk of mono I noted above was definitely left-channel only - not convinced that this is typical, but it's definitely what happens sometimes.
left-channel only? all this time I've been thinking that mono meant that right and left channels are identical. please explain.
Quote:
Originally Posted by robkismet
and I forgot to mention in any posts that the problem is much worse if the computer has come back from being on standby
computer voodoo!
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  #9  
Old 2005-01-10, 06:08 AM
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Re: Weird playback problem

Quote:
Originally Posted by Five
left-channel only? all this time I've been thinking that mono meant that right and left channels are identical. please explain.
Well yes, it is, usually, with them playing the non-wide stuff (better explanation in my main post). But the incident I'm referring to now, the contents of the right channel vanished (first few seconds of Innervision by SOAD), and there was just silence in the middle until it kicked. So it was like the contents of the left had been dragged into the middle (i.e. both speakers playing back the contents of the left). This is getting so complicated that I can't even explain what I mean using proper English anymore
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  #10  
Old 2005-01-10, 06:41 AM
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Re: Weird playback problem

OK here we go, some clips.

Example 1 is the revelant sample taken straight from the source mp3. Oh that makes me a pirate. Go me.

Example 2 seems to be the widest stereo profile I can get, which worries me cos there's quite a lot of bleed, but while all the more reason to get a new soundcard, isn't the problem at hand.

Example 3 gives the best range of the lot, but it's short and changes a lot, so best open up in a waveform viewer:
0.2s-0.5s is "stereo"
0.5s-0.7s is left-channel-mono
0.7s-1.2s is probably left-channel-mono, or possibly both channels mixed to mono
then it's back to "stereo"

I haven't been able to generate an example of mixed mono this morning so I'm swaying back towards the idea that it's always the left channel that shows up in the middle. However I am increasingly establishing that there are various levels of the problem and not just an on-off.

Example 4 just shows how pausing the playback (at 13s) can get things back on track. Doesn't sound like the audio at the beginning of this example suffers any frequency loss, in fact the only bit of that I've got here is the 0.7-1.2s part in Example 2, but that's hopefully enough to hear what I'm talking about.

Enjoy!
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  #11  
Old 2005-01-10, 06:49 AM
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Re: Weird playback problem

Quote:
Originally Posted by robkismet
Enjoy!
haha

okay, when I get home tonight I'll analyze the heck out of these and post all the information I can.
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  #12  
Old 2005-01-10, 05:50 PM
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Re: Weird playback problem

ahhah, just to make it even more fun, got a good solid example of the classic prolonged mono-whatever, simply remedied by pausing playback briefly halfway through.

I just had my first rush of nearly-panic-mode about exams. argh.
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  #13  
Old 2005-01-11, 12:39 PM
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Re: Weird playback problem



...just wanted to start with that. I'm puzzled as hell by all this, my only comfort is that it's not happening on my computer!! I feel bad for you, when you love music as much as we here all do, a problem like this really sucks.

I didn't come up with very much, I've spent about an hour pouring over these examples.

I see what you mean now by the left-channel mono thing. The left channel seems to take over, perfectly demonstrated with the example where there's supposed to be silence in the left and guitar in the right... but there's silence in both. Why? I dunno! The other parts where the volume drops and sound is almost mono, I took a close look and the sound is indeed nearly mono but is not perfect mono. That and the way the volume drops suggests stongly that something very strange is going on involving the L&R channels getting mixed together, plus something's happening with the phase. Of course, there's also the issue that there's sound in the left channel during the part where there's only supposed to be sound in the right channel. I found a small bit of useful evidence here:
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  #14  
Old 2005-01-11, 12:47 PM
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Re: Weird playback problem

Notice how the phase of the right channel is reversed! A-ha!! I couldn't find anything similar in the left channel (not to say it isn't there). I suspect that your right channel is out of phase and some of it has been blended (and the part blended into the left is IN PHASE ) with the left channel. Maybe the part that's been blended is in phase or out of phase, I'm not sure. I'd also guess that some of the left channel is somehow blended with the right, for sure it is during the "left channel mono" parts. What scares the hell out of me is the randomness of it all. Mixing channels and inverting phase suggests some kind of "super-surround!!!" kind of thing going on. But then that wouldn't explain the randomness.

Just in case, check Start > Settings > Control Panel > Sounds & Multimedia > Audio > Sound Playback > Advanced > Speaker Setup and tinker around with the settings in there and see if anything changes. This probably won't work and you've probably tried this, but I thought I'd mention it.
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Last edited by Five; 2005-01-11 at 12:54 PM.
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  #15  
Old 2005-01-11, 12:49 PM
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Re: Weird playback problem

and as mentioned before, check your windows mixer for any advanced settings available.
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