MPEG2 is a "lossless" compression

[drewson99]

Is this statement true? According to what I have read here in the forum this is not the case, but maybe I misunderstood.

This quote was taken from the easy joiner web site FAQ.

Andy

http://doeasier.org/joiner/faq.html#faq2

[Mirror_Image]

All MPEG is lossy compression.

http://bmrc.berkeley.edu/frame/research/mpeg/

[drewson99]

so what was the meaning of the statement, or is it just flat out wrong?

[jkl]

they are the first that i've seen to say lossless. mpeg compression can be as high 200:1. so the higher the compression the more you loose. i guess that at a lower compression of 30:1,pretty much average more or less, there is "less loss" then at the maximum compression. remember lossless does not mean no loss. any compression technique results in at least some loss. but mpeg is generally known as lossy compression.
btw, i wanted to add this quote from sonic's website-

"The act of converting a video stream to MPEG-2 format using a “live” source is called "encoding”, and is done either in software or hardware. "Transcoding" refers to the act of compressing a video clip from a file on your hard drive and is typically done in software only."

so i guess a lot of you encoders out there should really call yourselves transcoders.

[Spicuzza]

According to your link they wrote quote:

"MPEG-2 is a compressed digital format that is used in DVD authoring and DSS satellite dishes. It is considered a "lossless" compression. This is what allows for large video files to fit on a DVD disk."

They never said "MPEG2 is a "lossless" compression" those are your words!

I think most people would agree that commercially produced DVDs can be "considered" lossless.

[drewson99]

Now you did the same thing I did!!!!

You may be right, some people may consider commercially produced DVDs to be lossless (not I) but the quote was referring to MPEG2 (MPEG2 itself, in all its forms, the format itself) NOT commercially produced DVDs. Commercially produced DVDs only portray a minute cross-section of MPEG2 use by all people.

Andy

[adam]

Under no circumstance can a dvd be considered lossless. Lossless compression means all of the original information is preserved so that it can be recovered during decompression. Mpeg2, and any other form of mpeg encoding for that matter, is lossy compression so dvds are inherantly lossy regardless of what bitrate the content is encoded in. In actuality all comercial dvds are highly compressed and a great deal of information is lost from the original master film source.

That FAQ is completely wrong. Their definition of mpeg2 doesn't even make sense. If you want accurate info about mpeg2 go to the link Mirror_Image posted.

[drewson99]

took the words out of my mouth. technically, when you leave the celluliod you begin loss, as no form of compression will be able to represent the images composed of light-sensitive silver.

Andy

[adam]

Well that may be a little too technical. The quality loss you are talking about is inherant in any conversion, but not necessarily in any compression method. When you talk about lossy vs lossless compression you have assume you have a digitized source. In your example if you encoded using a lossless codec the loss of information would be caused from the digitizing of the film, not the compression method. There are lossless forms of compression, mpeg2 just isn't one of them.