Embedded Media Processing
Covering the entire spectrum of EMP-related design issues, this practical book will be an invaluable aid to every engineer working with EMP, from the beginner to the seasoned expert.
TABLE OF CONTENTS Embedded Media Processing
Compression/Decompression
Over the past decade or so, image, video and audio standards all have undergone revolutionary changes. As Figure 6.26 conveys, whereas historical progress was primarily based on storage media evolution, the dawn of digital media has changed this path into one of compression format development. That is, once in the digital realm, the main challenge becomes "How much can I condense this content while maximizing attainable quality?" Naturally, consumers view this format proliferation as a distraction that obscures the real prize access to a plethora of multimedia content.
Figure 6.26: Historical progression of media
Lossless versus Lossy Compression
"Lossless" compression implies that the original content can be reconstructed identically, whereas "lossy" compression allows some degradation in reconstruction quality in order to achieve much higher compression ratios. In JPEG, for instance, lossless compression typically achieves ratios of perhaps 2:1, whereas lossy schemes can compress a source image by 10:1 or more.
So what does image or video "quality" really mean? Well, it really entails several different measures. For instance, what's the pixel resolution compared with the image size? Also, how much color depth(bits per pixel) exists? For video, is the frame rate high or low? Too low a frame rate will cause noticeable flicker. Finally, quality can be measured by what is sufficient for the application. Given the intensive processing that video demands, it's advantageous to strive for quality that's "good enough" for an application, but not excessively expensive.
In the compression domain, the required level of quality translates...
Copyright Elsevier Inc. 2006 under license agreement with Books24x7
