tTesting of Nikon D-90 in May's Issue

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tTesting of Nikon D-90 in May's Issue

Postby vonholtz » Sun May 03, 2009 4:50 pm

In the testing and Analysis section of your tests for the four DSLR's in the May issue, you stated that the video files in the D-90 were compressed. Being a D-90 owner, I thought this was wrong and when I checked the file extension of my videos which I had taken with the D-90, I found that they were '.avi' files. 'AVI' files from what I have worked with and understand are not compressed. I have worked with this type of file in my video editing sessions and found them to take a lot of space. In fact I have an 8 gig memory card in my D-90, and it is only capable of holding 20 minutes worth of video at the camera's highest resolution. Please let me know if I am wrong on this. -- Paul
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RE: tTesting of Nikon D-90 in May's Issue

Postby brianb » Sun May 03, 2009 5:06 pm

[quote]'AVI' files from what I have worked with and understand are not compressed.[/quote]
Sometimes they are ... to play an AVI file in e.g. Windows Media Player, you need the appropriate decoder, which should be loaded from the device driver disk supplied with the camera. The camera manufacturer can essentially do what they want. Note that web cams almost always use compression, how much compression is used depends on the frame rate, high frame rates need quite heavy compression in order to cope with the limited bandwidth on a USB v1 connection. The Imaging Source cameras do record "raw" (and therefore need a USB v2 connection) but you still need decoder software to play back the AVI. Registax can manage without the IS decoder, but Windows Media Player will turn its nose up if you try to play back an AVI recorded from a DMK camera on a system that hasn't had the Imaging Source DMK drivers installed.

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RE: tTesting of Nikon D-90 in May's Issue

Postby lukeskywatcher » Mon May 04, 2009 8:53 pm

The Nikon D90 uses an AVI file format called "Motion JPG", which is a compressed file system.
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RE: tTesting of Nikon D-90 in May's Issue

Postby pulsar » Thu May 07, 2009 10:46 pm

[:D] I like AVI'S [:D]
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RE: tTesting of Nikon D-90 in May's Issue

Postby Pete Lawrence » Fri May 08, 2009 7:36 pm

AVI is a bit like the TIFF of the image world in that it's simply a carrier format for whatever data the originator wants to put into it. The nature of the data is held in the header of the file and it's this which determines whether it's uncompressed or compressed. Compression takes essentially two forms in that you can have lossy compression where information is lost from the original or lossless where the data is compressed but nothing is thrown away. The way the data is compressed and ultimately decompressed for replay in an AVI file is via a codec. In the case of the D90 the codec used is the MJPEG as Paul (Lukeskywatcher) stated.

In summary, if you see a file with an AVI extension, you can't tell whether it contains compressed data or uncompressed data.
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RE: tTesting of Nikon D-90 in May's Issue

Postby lukeskywatcher » Mon May 11, 2009 1:30 am

[i][b]In summary, if you see a file with an AVI extension, you can't tell whether it contains compressed data or uncompressed data. [/b][/i]

True. But is it fair to say/assume that any digital camera/DSLR camera that has video capture function most likely does use a compressed data file, whereas any camcorder uses an uncompressed data file?
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RE: tTesting of Nikon D-90 in May's Issue

Postby pulsar » Mon May 11, 2009 1:30 am

My mini dv camcorder only creates in videots. Vob and Ifo files which are quite a pain to convert to avi which is very user friendly I find as I use them a lot for video and musical applications.
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