[Bug 661909] Remuxing gravity.mpeg doesn't work

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=661909
  GStreamer | gst-plugins-good | git

--- Comment #6 from Vincent Penquerc'h <vincent.penquerch at collabora.co.uk> 2011-11-09 19:43:48 UTC ---
What a WTF ride :D

So, it took me a while to realize that no demuxer was plugged by decodebin2,
because there are two pipelines: a first one for discovery, and a second one
for transcoding, and grepping for "creating element" showed everyhting I
expected.
Still, it was plugging in a MPEG video pipeline all fine, hiding that demuxer's
absence.

In the end, it turns out the bug was in transmageddon :p
For whatever reasons, a muxed MPEG stream has a media type of "video/mpeg,
systream=(true)", while the video inside has "video/mpeg,
systemstream=(false)".
On the second (transcoding) pipeline, transmageddon choses to set the caps
property to the contained codecs, to prevent decoders from being plugged.
However, it choses to remove all fields from the video media type, which gets
rid of "systemstream=false", and ends up matching "systemstream=true".
So autoplugging stopped just before plugging the demuxer, as caps were deemed
final.

The following patch (disabling the code which removes fields from the video
codec media type) fixes the issue, but I guess you may want to replace this
with something that special cases systemstream, as whetever issue caused you to
do this would likely show up again.

I tested by remuxing to Matroska. The remuxed output looks chuggy, but that's
another issue.


diff --git a/src/transmageddon.py b/src/transmageddon.py
index 51dfb5f..d61de41 100644
--- a/src/transmageddon.py
+++ b/src/transmageddon.py
@@ -706,7 +706,7 @@ class TransmageddonUI:
                textdata=gst.Caps.to_string(self.vsourcecaps)
                sep= ','
                minitext  = textdata.split(sep, 1)[0]
-               videocodec = minitext
+               videocodec = textdata #minitext
            self.outputdirectory=self.videodirectory
        else:
            self.outputdirectory=self.audiodirectory

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