Book Image

Learning VirtualDub: The Complete Guide to Capturing, Processing and Encoding Digital Video

Book Image

Learning VirtualDub: The Complete Guide to Capturing, Processing and Encoding Digital Video

Overview of this book

VirtualDub is one of the most popular video processing applications for Windows. As an open source application, it's free, and is constantly updated and expanded by an active community of developers and experts. VirtualDub is particularly popular for capturing video from analogue sources such as video tape, cleaning up the image and compressing it ready for distribution over the Internet. This book provides a rapid and easy to use tutorial to the basic features of VirtualDub to get you up and running quickly. It explains how to capture great quality video from various sources, use filters to clean up the captured image and add special effects. The book also shows how to use VirtualDub to cut and paste video to remove or insert sequences, including removing ad breaks or trailers. It goes on to cover the art of effective encoding and compression, so you end up with great quality videos that won't hog your bandwidth forever. VirtualDub is the fastest and most effective way to capture, process and encode video on your PC. This book gets you started fast, and goes on to give you full control of all the features of this legendary tool.
Table of Contents (14 chapters)
Learning VirtualDub
Credits
About the Authors
Introduction

Cropping and Resizing


Before we continue with the specifics of cropping and resizing, it is essential to understand the notion of aspect ratio. As you might imagine, it is the ratio of width over height. In mathematical notation:

A lot of the time, this is given. For example, video recorded by my camcorder has an aspect ratio of 4:3 (4 units across to 3 unit’s height), although the size is 720x576. Calculating the aspect ratio from the pixel resolution would give 5:4, which is not correct. This is because the pixels are not square in most analogue devices; the pixel aspect ratio is not 1:1 and it is not the case on computer screens. Because of this, you will need to know the aspect ratio beforehand or, guess it!

Often it is necessary to resize i.e. change the dimensions of a video, usually to increase the coding efficiency and therefore reduce the size of the output. Other reasons include conformance to video standards; if you plan to burn your video onto PAL VideoCD for example, you will...