March Networks MNM4 Codec

Another interesting codec implementation!

When the disk produced by the DVR autoruns, the above menu appears. It all appears quite self explanatory.  However, on an XP and a Win7 PC, even when ONLY the Run Evidence Reviewer has been selected, it has placed files into the PC. Importantly, these were the codec dll and the necessary registry entries. Worryingly, there is no notification of this and no un-install to remove them. Rather naughty!

Due to this version being a couple of years old, you may come across newer versions that don’t install anything.

The player is pretty heavy but relatively easy to navigate around and make sense of.

The video files are inside ‘Case’ Folders. They are standard AVI format utilising a proprietary March Networks Codec with a 4CC of MNM4. The fact that you have run the player now means that the codec is now installed in your PC – probably without you realising.

It appears quite an old codec, but it’s interesting to see some of the analysis results.

Gspot appears to be telling me that the file has 242,904 frames although only 25,234 are being read as part of the GOP structure. At 30 FPS this makes 8096.8 seconds… or just under 2 1/4 hours.

AVInaptic reports that the mpeg is made up of 1687 Frames :

I-VOPs: 169

P-VOPs: 1518

So, where are the rest, and what are they.

In order to take a closer look, I utilised Mencoder to remove every duplicate frame from the file. I used the same method as described in the FJHT article. After adding the Codec into the codecs folder and adding the following entry into the codecs.conf file, I could play the video in SMplayer.

videocodec MNM4
info “March MPEG4”
status buggy
fourcc MNM4
driver vfw
dll “mnmpeg4.dll”
out RGB24,RGB32,BGR32,BGR24 flip

I have added this to my SMplayer that is downloadable from my shared BOX on the right.

Using Mencoder I transcoded to an interim file to assess non duplicate images. For this test I used the lossless FFmpeg HuffYUV codec to keep sizes manageable. This is a great interim codec suitable for further transcoding to Video DVD etc.

mencoder originalfile.avi -noskip -vf decimate=-0.99999 -ovc lavc 
-lavcopts vcodec=ffvhuff -nosound -of avi -o outputfile.avi

It parsed all 242, 904 frames and resulted in a clean video file with no duplicates.

Spot the issue! There were 6117 Frames…,

The first and the last frame was a match to the original file. I chose three points in the video file where there was vehicle movement and by comparing frame by frame, they matched exactly with no loss of frames.

From reviewing the file in the original player, and by watching very carefully, it would appear that some clever motion detection is being utilised within the mpeg video. Due to the proprietary nature of the codec, a lot of in depth analysis is not possible. This serves as good caution to never rely fully on standard analysis programs when dealing with non standard video.

During testing, I used the software to extract a still image.

Although the added Metadata is great for single images, the limitations in the software are going to cause a few headaches if you require to do anything more in depth.

In conclusion, although you can review and pre-process the files using Mencoder, verification of dropped frames etc is pretty difficult. It would all really depend on the nature of your requirements. Also, due to the change in frame rate of times when there is limited or no motion, any time or frame rate re processing is impossible.

The Mencoder method is ideal (as it only takes a couple of minutes ) to quickly grab all the images to assess movement or possible further clarification without being hindered by the proprietary player.

Hope it helps…. and onto the next one!

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