The audio is really really bad (with lots of noise) under windows when gst-launch-1.0.exe is used with the playbin command for mp3 or ac3 files or videos with these as audio. Tested this on my Laptop and my Desktop PC.
Both have Windows 7 64 bit.
I used the install files from here:
http://gstreamer.freedesktop.org/data/pkg/windows/
tested these versions:
gstreamer-1.0-x86-1.0.7.msi
gstreamer-1.0-x86-1.0.8.msi
gstreamer-1.0-x86-1.0.9.msi
gstreamer-1.0-x86_64-1.0.9.msi
All have the same result.

Example command lines:
gst-launch-1.0.exe playbin uri=file:///c:/temp/some.mp3
or for mp4 h264 video file with ac3 as audio:
gst-launch-1.0.exe playbin uri=file:///c:/temp/somevideo.mp4
Same when mp4 or mkv file with mp3 audio is used.

AAC for audio is fine.

I tried different mp3 and video files.

If I use this command:
gst-launch-1.0.exe filesrc location=some.mp3 ! mpegaudioparse ! avdec_mp3 ! autoaudiosink
the audio is perfect

The files work in an older GStreamer 0.10.x version (using playbin or playbin2).
I did not find an older 1.0.x version to test it.

As I said it also does not work on my Desktop PC so it does not seem to be a sound driver problem.

We use GStreamer in an application and want to just use playbin for video files but with these issues porting to the current version is not possible.

(I am on holiday for the next 2 weeks and can't therefore not answer any questions.)

thanks for the help