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Compression

FFmpeg: The ultimate Video and Audio Manipulation Tool

February 24, 2012 by slhck. 15 comments

What is FFmpeg?

Chances are you’ve probably heard of FFmpeg already. It’s a set of tools dedicated to decoding, encoding and transcoding video and audio. FFmpeg is based on the popular libavcodec and libavformat libraries that can be found in many other video conversion applications, like Handbrake.

So why would you need FFmpeg? Got a video in an obscure format that every other player couldn’t recognize? Transcode it with FFmpeg. Want to automate cutting video segments out of movies? Write a short batch script that uses FFmpeg. Where I work, I constantly have to encode and process video material, and I’d never want to go back to using a GUI tool for doing this.

This post is a follow-up on Video Conversion done right: Codecs and Software, where I discussed the various codecs and containers that you can find these days. For a quick overview, I’d suggest to read this one as well, because it covers some important basics.

Now, let’s dive into the more practical aspects.

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Video Conversion done right: Codecs and Software

November 7, 2011 by slhck. 8 comments

Videos are everywhere. They come in quite a few different formats – all with their own advantages and disadvantages. Converting videos from one format to another is a very simple task, given the right tools. In this post, we will go through the most popular video codecs and the software you need to get the best results.

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Compression and Encryption: The ZIP Years.

April 2, 2011 by flibs. 1 comments

In a comment to my last post Compression and Encryption, nhinkle asked:

Do you know then how encrypted ZIP files work? Encryption seems to be built into many encryption formats like zip, rar, 7z, etc. Do these usually compress and then encrypt, or somehow do both at once?

Well, ZIP handles this in its own special way. First let’s look at how a ZIP file is made up. A ZIP file consists of one or more ‘file entries’ – blocks of data that make up the actual content of the zip file, followed by a final ‘central directory’:

ZIP

As you can see each file in the ZIP file has its own local header which contains the information about how the file is compressed. This allows each file in the ZIP file to be compressed in a different way – from “Store” (no compression – ideal for adding pre-compressed files) right up to the maximum and slowest compression available.

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