Video Compression

[pulkit]

Can anyone please explain how video compression works ? And wether convertion to a compressed format necessarily result in loss of quality ?

[JaKiri]

It works the same as any other compression; cutting out useless bits. Basically.

 

As for 'loss of quality' it depends what you mean; it is a sampling technique, which, by definition, can never, no matter the sampling rate, have precisely the same quality as the original. However, it's fairly easy to create compressed files which cannot be easily told from the originals.

[bloodhound]

most of the video compression works by using key frames. they are like snapshots. and the video is compressed by analysing the difference between those keyframes

[Dave]

MPEG4 uses a rather nice technique of trying to distinguish the foreground from the background, and then (since the background shouldn't theoretically change all that much), it's simply a matter of looking at how the foreground changes.

 

It's a lot more complex than that, but that's the basic idea.

[pulkit]

Could you please tell me the names of some of the algorithms involved in such compression techniques ?

[Dave]

Just do a google for MPEG (or similar), that should give you a pretty detailed summary of what algorithms each standard uses.

[mossoi]

http://www.cctv-information.co.uk/ucompression.html

[Guest James]

Hello, I recently purchased DVD stuido pro and with it comes compressor. I have some dv footage on final cut pro that I need compressed so that I can put the footage on a dvd. I've been reading compressor but i'm having trouble making it work. Sometimes the sound doesn't transfer over. Any help would be great. Thanks for your time.

james

[5614]

i dont know why that happens james, may i suggest re-installing your software, and maybe contacting the software's manufacturer,

 

this is possibly a bug in the program, which hasnt been fixed yet, try downloading a patch from the website.

 

alternatively, try the programs helpl menu, possibly there is a sound box, which you must tick, for sound to be compressed with the video, and default it 'off' im not sure, but check the options,

 

and check that the sound format is compatible with the program, or that the program is compatable with the sound format, and video format, for that matter, it should be, but worth a check.