Chromium web browser not showing mp4 videos

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PROBLEM ::
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embedded playback of mp4 videos works in Firefox, fails in Chromium

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REPRODUCE ::
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examples are the videos in coursera.org If you are signed up for ml class,
start chromium-browser with url
https://class.coursera.org/ml/lecture/view?lecture_id=1
If chromium-codecs-ffmpeg-extra is not installed, which it isn't by default, you get a black screen for the video.
Reproduced on Ubuntu12.04 and 11.10
    chromium-browser --version
Chromium 18.0.1025.151 Ubuntu 12.04

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SOLUTION ::
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Ubuntu software center should suggest the addon plugin equivalent to:
sudo apt-get install chromium-codecs-ffmpeg-extra

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DETAILS ::
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To tell if the library is installed:
dpkg-query -l chromium-codecs-ffmpeg-extra

The needed library is installed as:
/usr/lib/chromium-browser/libffmpegsumo.so

I found this out with the command
dpkg-query -L chromium-codecs-ffmpeg-extra