On 22 Jul 2015 07:58 PM ,Ma <Doff@Modo.de> wrote:
> On 2015-07-23 01:45:36 +0000, Weener said:
>
> > Ma <Doff@Modo.de> wrote in news:201507222043245273-Doff@Modode:
> >
> >> most people in
> >> this group will use compression when posting and you have to decompress
> >> the file that they post so it's not like they'd have an exact copy once
> >> extracted, I thought either they are ignorant or just bitching to be
> >> bitching.
> >
> > Winrar and 7zip do indeed produce exact copies once extracted. Csv's and
> > crc values with PiCheck are what Vlad collectors use to verify them. Just
> > so you know.
> >
> > Weener
>
> ZIP is a very popular compression algorithm supported by many popular
> programs such as WinZip, 7-Zip, and recent versions of Microsoft
> Windows. ZIPping a file or set of files can often reduce their size
> significantly at the cost of needing to be unzipped before they can be
> used.
>
> The short answer
> To understand why that might be, we need to look into how compression
> works at a high level.
> About compression
> While the specifics of many different compression algorithms is often
> compression are actually fairly simple.
> The idea is that information stored on disk is often stored in a way
> purposes, but as a side effect, there may be redundant information in
> the data that could be represented differently.
> Consider the following text:
> This is a row of 10 asterisks: ********** followed by text.
> plus character, but rather an indicator that the next two characters
> are a count, and the third character the character that should be
> repeated that many times, we get this:
> This is a row of 10 asterisks: +10* followed by text.
> with 10 asterisks. The original uncompressed text is restored.
> This is a row of 10 asterisks: ********** followed by text.
> worked.
> Here's a single plus sign: + followed by text.
> The problem is that because it actually contains the plus sign, the
> just let it be. If we do, the decompression algorithm will look at it
> wrong.
> Unless we specially encode the plus character:
> Here's a single plus sign: +01+ followed by text.
> next three characters are a count (one, in this case) of the number of
> decompression algorithm works.
> was crafted to make it easy to show, but even the most advanced
> compression algorithm will have situations where compressing particular
> original.
> Compressing already compressed data
> One of the most common ways that compressed data can end up larger than
> the original is if the original is itself already compressed.
> This is a row of 10 asterisks: +10* followed by text.
> What happens if we try to compress that data again? Well, as we saw,
> This is a row of 10 asterisks: +01+10* followed by text.
> Or rather compressing the already-compressed data made it larger.
> This happens most reliably when you compress twice using the same
> something twice makes the second zip larger than the first. But ZIPping
> something bigger than the original.
> With that as background, we can finally explain our answer to the question.
> Pictures, music, and videos are already compressed
>
> One of the most common ways that compressed data can end up larger than
> the original is if the original is itself already compressed.
> Pictures in popular formats such as .jpg, .png or .gif are already compressed.
>
> Music files in formats like .mp3, .ogg, .aac, and so on are already compressed.
> Video files in formats like .wmv, .m4v, .mov, and more are already compressed.
> using, compressing an already-compressed file at best does very little
> and at worst makes the file bigger.
> movie, or an MP3.
>
>
> I use KeKa for folders to zip with 7z for cross-platform use and with
> NO COMPRESSION!
> For movie files like mpg or mp4 I simply split the file. Linux and Unix
> users can use the split command in bash, windows users can use
> HJSplitter, OSX users can use Split&Concat.
>
I hadn't read this thread before. And now that I have, being a newbie to usenet and all, I am confused. Katyalover told me to use Winrar and set it to "Store" so that it wouldn't compress the files. Does it compress them anyway? I haven't downloaded many vids from usenet and avoided the ones from torrents because of embedded viruses. But I have used Quickpar on them as of late. Is that a safe way to do it? Most of my vlad collection was downloaded on dialup so I always went for small files previously.
Lucky
I'm reading this in a.b.v.p. and hopefully posting elsewhere
--
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