There are two types of compression, lossy and lossless. Lossless
compression allows you to decompress the file at any time and see a
bit-for-bit copy of the original. This means that you can use lossless
compression on any type of file since the content of the files doesn't
really get effected. Zip, rar, gzip and bzip are all examples of
general purpose lossless compression.
Lossy compression can examine certain types of files and remove data
that "seems unneeded". Lossy compression is most frequently used on
media such as images, video and audio. Mp3, jpg, and mpg are all
examples of file types that are compressed using lossy compression.
Every time you use lossless compression, you lose a little more
information - the quality of the information decreases. The image
becomes more pixelated, colors are removed, sound becomes garbled, etc.
Lossless compression doesn't work well on them because they are already
highly compressed - so much so that certain pieces of data in the file
has been irreversibly removed to make the data easier to compress.
So, you have an mpg file, a file that is already highly compressed using
lossy compression. How do you make the file smaller? There are only
two ways to get that file smaller: the first is to lower the quality of
your video. The second is to switch to a higher quality compression
engine. This will also cause some loss in quality, but not as bad as
trying to make mpg work better. This second solution may not be
possible. Mpg is a container, not a compression technology. We would
need to know if your mpg file is already an h.264 file. If it is, then
you are already using one of the highest quality video compressors
available. You can find out what the content of the mpg file is by
right-clicking on the file and chosing file properties. I'm not a
Windows user, so you may need to get further help to determine this.
Once you know what type of data is in the mpg file, let us know, and we
can tell you if it's even possible to make it a smaller file without
sacrificing too much quality.
--David
On 09/03/2011 07:09 PM, IKnowComputers wrote:
>
> I need something with the best ratio. I am trying to compress mpg
> files. I have tried zip and rar and get little space savings. Any ideas.
>
>
[Non-text portions of this message have been removed]
http://tech.groups.yahoo.com/group/simplycomputers2
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