Flac vs Lame

In a previous post I discussed lossless audio encoding and presented a Bash script using flac to rip and process CD audio files. I also commented on how the psycho-acoustic model used in a MP3 encoder will dominate encoding as bit-rate increases, without much quantitative evidence. In this post, I present some.

The Minimalist Calculus Cheat Sheet

We do not know closed form solutions for all optimization problems, even when they are somewhat innoccent-looking. One of the many possible methods in such as case is to use (stochastic) gradient descent to iteratively refine the solution to the problem. This involves the computation of… yes, the gradient.

In its simplest form, the gradient descent algorithm computes the gradient of an objective function relative to the parameters, evaluated on all training examples, and uses that gradient to adjust the model’s parameters. The gradient of a (not necessarily objective) function has the general form

Looking At Flac Compression Ratios

In a previous post, I told you about a short script to rip and encode CDs using Flac, and I discussed a bit about how LPC works. In this post, let us have a look on how efficient Flac is.

Let us use a quantitative approach to this. Since I have a great number of songs, we can use statistics to give us a good idea of what kind of compression we can expect.

Wallpaper: The Color of NOT having Backups

(The Color Of NOT Having Backups, 1920×1200)

You can find more wallpapers here

(Random Musings) On Floats and Encodings

The float and double floating-point data types have been present for a long time in the C (and C++) standard. While neither the C nor C++ standards do not enforce it, virtually all implementations comply to the IEEE 754—or try very hard to. In fact, I do not know as of today of an implementation that uses something very different. But the IEEE 754-type floats are aging. GPU started to add extensions such as short floats for evident reasons. Should we start considering adding new types on both ends of the spectrum?

The next step up, the quadruple precision float, is already part of the standard, but, as far as I know, not implemented anywhere. Intel x86 does have something in between for its internal float format on 80 bits, the so-called extended precision, but it’s not really standard as it is not sanctioned by the IEEE standards, and, generally speaking, and surprisingly enough, not really supported well by the instruction set. It’s sometimes supported by the long double C type. But, anyway, what’s in a floating point number?

Medians (Part III)

So in the two previous parts of this series, we have looked at the selection algorithm and at sorting networks for determining efficiently the (sample) median of a series of values.

In this last installment of the series, I consider an efficient (but approximate) algorithm based on heaps to compute the median.

Wallpaper: Frontières imaginées

(Frontières imaginées, 1920×1200)

You can find more wallpapers here

Wallpaper: Sibérie minimaliste

(Sibérie Minimaliste, 1920×1200)

You can find more wallpapers here

Lossless Coding of CD Audio

Once upon a time, I discussed how to pick bit-rate for MP3, while considering re-ripping all my CDs. But if I’m to re-rip everything, I might as well do it one last time and use lossless compression.

In this post, we’ll discuss the simple script I cooked up to do just that, and a bit on how Flac works, and how it compares to MP3.

Suggested Reading: National Audubon Society Guide To Photographing National Parks

Tim Fitzharris — National Audubon Society Guide To Photographing National Parks (Digital Edition) — Firefly Books 2009, 192 pp. ISBN 978-1-55407-455-6

(Buy At Amazon.com)

Contrary to what the title may indicate, this book has little to do with actual digital photography techniques for landscapes or natural wonders; it is rather a tourist guide of everything you should see in the major american national parks. After expediting the basics of landscape photography, the guide leads you into a detailed journey into the United States major national parks, giving you all the good hints as to how to reach this-or-that natural wonder, what time of year, or even the time of day will lend itself the best for photography.

While this seems moderately interesting for a foreigner (especially if one doesn’t really want to visit all the state parks), the book is entirely redeemed by Fitzharris’ absolutely superb photography. A must get, especially if you’re interested in landscape photography.