Analysing MJPEG-compressed movies with DIAdem

[smaerchy]

Hi!

I am trying to find out whether and how good MJPEG movies can be analysed with DIAdem.

I want to capture 4 video signals (PAL, 720x576, 25fps) with one PC. The video signals have to be compressed before they are saved to hard disc in order to reduce data. Afterwards I want to analyse the movies together with other measuring data using DIAdem 10.1.

I heard that MPEG-4 movies wobble in DIAdem and MPEG-2 works pretty well. But since most hardware compression devices only support MPEG-4 or MJPEG, I would like to use MJPEG. Can anybody tell me how MJPEG movies can be analyzed using DIAdem???

Is there anybody who has experiences with this compression type?

Thanks for any input

Sandra

[Ralf_Mueller]

Hello Sandra,

We tested two codecs which can be used for MJPEG videos: both the MainConcept Codec and the FFdshow codec worked well (without wobbling) in DIAdem VIEW.

An important question you didn't answer is how long are the videos you want to capture. For example 8 minutes of PAL video results in approx. 2GByte of raw (uncompressed) data. Of course you will get less data on your hard disk because the signal will be compressed. But the more compression you use the more CPU power you will need. And the synchronization with measurement data and between different videos requires a significant amount of overhead on top.

When you are synchronizing four videos from one hard disk simultaneously the heads of the hard disk have to jump very quickly to read the videos alternately. In our tests we had no problems with two or three videos but to synchronize four videos we had to split the videos on two different hard disks.

At the end it depends heavily of your PC hardware how well DIAdem can synchronize four videos simultaneously. Therefore we suggest to test your application which can be done with the DIAdem demo version. Usually the codecs are available in a demo mode as well and example videos can be found in the internet.

Please ask if you have further questions,

Ralf
National Instruments

[smaerchy]

Hi Ralf,

I just wanted to ensure that DIAdem can handle MJPEG-movies before buying expensive frame grabbers which can only compress to MJPEG.

Actually my videos will be at most 30 minutes long (usual are 20 minutes), but only one of the videos really has to be full resolution and full frame rate. Maybe I can reduce resolution and frame rate of the other videos in order to reduce amount of data…

Well, I will really have to test it J

But thanks for your help!

Sandra