[pitivi] previewers: Avoid changing number of channels in proxies

[Thibault Saunier <tsaunier src gnome org>]

commit d9614c5736abd42256be097f1d827c1dcd8e4db5
Author: Thibault Saunier <tsaunier igalia com>
Date:   Tue Mar 3 17:27:02 2020 -0300

    previewers: Avoid changing number of channels in proxies
    
    We were forcing 1 channel because of the way the previewer was
    implemented.
    
    Fixes https://gitlab.gnome.org/GNOME/pitivi/issues/2338

 pitivi/timeline/previewers.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/timeline/previewers.py b/pitivi/timeline/previewers.py
index 531b1cf1..6af7a3f9 100644
--- a/pitivi/timeline/previewers.py
+++ b/pitivi/timeline/previewers.py
@@ -170,9 +170,9 @@ class WaveformPreviewer(PreviewerBin):
 
     def __init__(self):
         PreviewerBin.__init__(self,
-                              "audioconvert ! audioresample ! "
+                              "tee name=at ! queue ! audioconvert ! audioresample ! "
                               "audio/x-raw,channels=1 ! level name=level"
-                              " ! audioconvert ! audioresample")
+                              " ! fakesink at. ! queue")
         self.level = self.internal_bin.get_by_name("level")
         self.debug("Creating waveforms!!")
         self.peaks = None