Try svn version: 
svn checkout http://qmmp.googlecode.com/svn/branches/qmmp-0.2/ qmmp-0.2 

Tried r809 on the branch, same results.

OK, try another player. If qmmp only has this problem, show its output during
starting playback.

> OK, try another player.

I have dozens of multimedia programs on this computer, and all work fine with OSS
audio output.

> If qmmp only has this problem, show its output during starting playback.

OutputOSS: uninitialize
DecoderMAD: deleting input_buf
DecoderMAD: deleting output_buf
SoundCore: creating decoder
ok
SoundCore: decoder was created successfully
DecoderMAD: 152 bytes skipped
DecoderMAD: Fixed rate detected
DecoderMAD: Total time: 12
DecoderMAD: 152 bytes skipped

OK, try r818. If the problem still exists, show output again.

I appreciate your persistence.  I build r818 from the branch, the results are still
the same, here's the output with a 12s MP3 which played at 1/8 speed:

SoundCore: creating decoder
ok
SoundCore: decoder was created successfully
DecoderMAD: 152 bytes skipped
DecoderMAD: Fixed rate detected
DecoderMAD: Total time: 12
OutputOSS: frequency=44100, channels=2, bits=16
DecoderMAD: 152 bytes skipped

With a 68s Ogg/Vorbis file, the speed was approx. 1/4:

SoundCore: creating decoder
ok
SoundCore: decoder was created successfully
DecoderVorbis: initialize
OutputOSS: frequency=44100, channels=1, bits=16
file info:
ARTIST =
TITLE =
ALBUM =
COMMENT =
GENRE = Other
YEAR = 0
TRACK = 0
LENGTH = 68

Testing a few different files, the speed seems to be 1/(4 * channels); 1/4 for mono,
1/8 for stereo.  Does that help?

OK, try again. I hope, it shows more useful info now.

Sorry, output and results are exactly the same.

May be qWarning() doesn't show messages under windows. Find outputoss.cpp file and
change all "qWarning" functions to "qDebug". Than try again. I consider, "/dev/oss"
doesn't support 44kHz.

Cygwin != Windows, and qWarning does show messages (I added one unconditionally to
verify).  I assure you that these files do play on other audio players with their OSS
backends.

OK, yet another attempt. Try to remove this lines from outputoss.cpp

    int flags;
    if ((flags = fcntl(m_audio_fd, F_GETFL, 0)) > 0)
    {
        flags &= O_NDELAY;
        fcntl(m_audio_fd, F_SETFL, flags);
    }

Sorry, no change. :-(

OK, try to increase sample rate. Change "m_frequency = freq" to something like
"m_frequency = freq*4" or 8. Does it change anything? 

Using freq*4, I got an additional message:

OutputOSS: can't set frequency, using 176400 instead

With freq*8, the message was 352800.  That comes from the if(m_frequency != freq)
conditional which you added.

Playback was still as slow.

Looks like "/dev/dsp" doesn't use samplerate settings. And I can't find any
differences in oss code between mpd, audacious and qmmp. 
I consider, this is last difference: 
- open(m_audio_device.toAscii(), O_WRONLY, 0);
+ open(m_audio_device.toAscii(), O_WRONLY);

Looking at the Cygwin sources, I see now that SNDCTL_DSP_GETODELAY is not supported.
 GStreamer and PulseAudio use SNDCTL_DSP_GETOSPACE as a backup.

If you're out of ideas, then I'll try to figure this out myself, and if I'm
successful, I'll propose a patch here.  I appreciate your efforts nevertheless.

Yes, you are right. I haven,t more ideas. So I'm waiting for your patches. 

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