[gst-devel] Audio caputure too fast and distorted.

Francis Rammeloo francis.rammeloo at gmail.com
Tue Feb 2 13:19:08 CET 2010

I am trying to make a screen casting tool based on the GStreamer libs.
The application combines a screen capture with the webcam video and
microphone streams. The pipeline is constructed using gst_parse_launch
from this text:

      mic. ! queue
           ! ffenc_wmav2 bitrate=100000
           ! muxer.
      desktop. ! queue
               ! ffmpegcolorspace
               ! videoscale
               ! videorate
               ! video/x-raw-yuv,width=640,height=400,rate=15/1
               ! videobox right=-320
               ! ffmpegcolorspace
               ! vmix.sink_0
      webcam. ! queue
              ! ffmpegcolorspace
              ! videoscale
              ! videorate
              ! video/x-raw-yuv,width=320,height=240,rate=15/1
              ! vmix.sink_1
      logo. ! queue
            ! jpegdec
            ! ffmpegcolorspace
            ! videoscale
            ! videorate
            ! video/x-raw-yuv,width=320,height=160,rate=15/1
            ! vmix.sink_2
      vmix. ! t.
      t. ! queue
         ! ffmpegcolorspace
         ! ffenc_wmv2 bitrate=700000
         ! muxer.
      t. ! queue
         ! ffmpegcolorspace
         ! dshowvideosink
      muxer. ! queue
             ! filesink location="opname.wmv"
      dshowaudiosrc name="mic"
      gdiscreencapsrc name="desktop"
      dshowvideosrc name="webcam"
      multifilesrc name="logo" location="chrome/skin/ivpv.jpg"
      videomixer name=vmix
                 sink_0::xpos=0 sink_0::ypos=0 sink_0::zorder=0
                 sink_1::xpos=640 sink_1::ypos=0 sink_1::zorder=1
                 sink_2::xpos=640 sink_2::ypos=240 sink_2::zorder=2
      tee name="t"
      ffmux_asf name=muxer

This produces an output file successfully, however there are a few issues:
- audio playback is a little too fast (around 25% too fast I think).
- audio is distorted there are crack and thud noises (similar to the
sound of raindrops when standing under an umbrella).

Does anyone have an idea how to fix these problems?

I am using windows (Vista and 7) and I use the WinBuilds distribution
on GStreamer (the most recent GPL release).


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