[gstreamer-bugs] [Bug 575736] New: mpeg2enc's bitrate parameter does not work properly

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-bad | Ver: 0.10.10
           Summary: mpeg2enc's bitrate parameter does not work properly
           Product: GStreamer
           Version: 0.10.10
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: gnucash at thoth.purplefrog.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


I attempted to reencode a 15-minute sample video using mpeg2enc.  I picked
bitrate=3180 since the CableLabs VOD standard specifies 3180000 bits/s.  When I
graphed the bit rate of the resulting stream the results were drastically
wrong.  It started out good, but after a few seconds exploded to 15Mbits/s with
spikes to 27Mbit/s.

I experimented with varying bit rates.  2750 Kbits/s worked for the entire
15-minute encoding.  2900 exploded near the end.  3000-3050 exploded in the
middle, went sane later on, and exploded again at the end.


gst-launch-0.10 -v filesrc location=/var/tmp/The\ Drinky\ Crow\ Show\ -\
Tunnel\ Girls.mpeg ! decodebin name=db ! queue ! videoscale ! video/x-raw-yuv,
width=352, height=480, pixel-aspect-ratio=1920/1056 ! mpeg2enc b-per-refframe=2
bitrate=2900  min-gop-size=15 max-gop-size=15 sequence-header-every-gop=true
aspect=2 ! ttvpeswrapper silent=true ! filesink location=/var/tmp/x/dc.m2v 
db.! queue  ! audioconvert ! ffenc_ac3 bitrate=192000 ! ttvpeswrapper
silent=true stream-id=189 ! filesink location=/var/tmp/x/dc.ac3

I have a screenshot of one of the graphs here:

http://www.purplefrog.com/~thoth/x/bitrate=3050.png


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