Slopjongs weblog » Programming

ID3 batch editing

slopjong — Mon, 30 Aug 2010 15:16:22 +0000

Some of my music had no interpreter and title tags set thus I wrote a little shell script to batch edit these ID3 tags. The filenames of the songs looked like “01 Interpret – Song Title.mp3″. In a few moments I wrote the following php script¹ which split the filename into the interpreter and the title.

All the python scripts listed here are using the library pytagger.

Unfortunately I forgot to strip the digits so all the interpreters had two leading digits afterwards.

I had to iterate over the files again. As id3.py creates new tag frames I had to write another script (fix_interpreters.py) that reads the old frames to get the old values.

#!/usr/bin/env python

from tagger import *
import sys, os, fnmatch, pickle, re

filename = sys.argv[1]

print "Processing '", filename, "'"

try:
  id3 = ID3v2(filename)

  if id3.tag_exists():
    interpret_frame = None
    for frame in id3.frames:
      interpretfid = 'TPE1'
      if id3.version == 2.2:
        interpretfid = 'TP1'

      if frame.fid == interpretfid:
        interpret_frame = frame
        break

    interpret = interpret_frame.strings[0]
    repaired = re.sub('^\d\d\s', '', interpret)

    print "Repairing "", interpret, "" => "",repaired,"""
    interpret_frame.set_text(repaired)

    # replace interpret frame
    id3.frames = [frame for frame in id3.frames if frame.fid != interpretfid]
    id3.frames.append(interpret_frame)
    id3.commit(pretend=0)

except ID3Exception, e:
  print("ID3 exception: %s" % str(e))

I didn’t want to rewrite the php script above because I thought that typing a loop in the shell would be easier (or at least faster).

for file in `ls -1 *.mp3`; do ./fix_interpreters.py $file; done

I tried it with this loop but ls -1 *.mp3 doesn’t list each mp3 file one per line as expected. Instead it splits the filenames after each whitespace. Thankfully to Greg Miller’s post about Handling Filenames With Spaces this wasn’t no problem anymore. I changed the loop into

find ./ -name '* *' | while read filename; do ls -ld "$filename"; ./fix_interpreters.py "$filename"; done

and ta-da, it worked.

PHP scripts can be executed in a shell. Use php -f script.php to execute a file or use -r instead of -f to run inline code. ↩

jQuery: eq() vs. get()

slopjong — Thu, 15 Jul 2010 17:07:32 +0000

There are several ways to access queried DOM elements. You get either a DOM element using get() or a jQuery object using eq(). This can be confusing while you try to call jQuery API functions on DOM elements.

The example shows how to get the first array element on three different ways.

Instead of using the filter method eq() you can combine the filter with the selector like this

var elem = $("li:eq(0)");

var elem = $("li:first");

To turn a DOM element into a jQuery object you can wrap it with jQuery(element) or $(element) if you’re not in conflict mode. But keep in mind that this creates a new object which ~~wastes~~ consumes memory so pay attention if you do this in a loop.

Java kills people

slopjong — Thu, 08 Jul 2010 14:48:42 +0000

www.youtube.com/watch?v=A-Rp6wMZ1-s

Matlab commands for feedback controls

slopjong — Mon, 14 Jun 2010 14:32:59 +0000

Here is a small matlab reference for feedback calculations or simulations:

roots: Find polynomial roots
poly: Convert roots to polynomial
conv: Convolution and polynomial multiplication
polyval: Evaluate polynomial
tf: Creation of transfer functions or conversion to transfer function
pzmap: Pole-zero map of LTI models
pole: Compute the poles of LTI models
zero: Computes the transmission zeros of LTI models
series: Series interconnection of the two LTI models
parallel: Parallel interconnection of two LTI models
feedback: Feedback connection of two LTI models
minreal: Minimal realization and pole-zero cancellation
step: Step response of LTI models

Accessing the right method in Java

slopjong — Tue, 20 Apr 2010 14:13:16 +0000

A inner class can call methods of an outer class.

public class Dummy1
{
	private class Dummy2
	{
		public Dummy2()
		{
			method();
		}
	}

	private void method() { }
}

So far so good but if the inner class has the same method this will be called instead. To avoid this ambiguity one can call the method in a more specific way. To be able to call the method of the outer class the prefix Dummy1.this can be added.

public class Dummy1
{
	private class Dummy2
	{
		public Dummy2()
		{
			Dummy1.this.method();
		}

		private void method() { }
	}

	private void method() { }
}

Urinal manual

slopjong — Sat, 10 Apr 2010 14:01:28 +0000

Based on the tikz flowchart example I created my first flowchart in Latex. Creating such a flowchart with Latex is not as easy as it looks like. Sometimes you don’t get an error message even if there is an error (especially missing semicolons) in the code. In my case pdftex just hang up. One thing was a bit tricky but first have a look at my code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}

\begin{document}

\pagestyle{empty}

% Define block styles
\tikzstyle{decision} = [diamond, draw, fill=blue!20,
text width=4.5em, text badly centered, node distance=3cm, inner sep=0pt]

\tikzstyle{block} = [rectangle, draw, fill=blue!20,
text width=4cm, text centered, rounded corners, minimum height=4em, minimum width=4.5cm]

\tikzstyle{line} = [draw, -latex']

\tikzstyle{cloud} = [draw, ellipse,fill=red!20, node distance=3cm,
minimum height=2em]

\begin{tikzpicture}[node distance = 3cm, auto]
% The nodes
\node[cloud] (business) {Business};
\node[block, below of=business] (person) {i:=person};
\node[decision, below of=person] (sex) { i.sex = male ?};
\node[decision, below of=sex, node distance=4cm] (sex2) { i.sex = pre-op transsexuel female ?};    

\node[block, right of=sex2, node distance=6cm] (execution_block_1) {i.enter(toilet)\\
i.open(trousers)\\
i.target(eyes, center)\\
i.target(hands, center)
};

\node[block, below of=execution_block_1] (open_bladder) { i.open(bladder) };
\node [decision, below of=open_bladder, text width=2cm] (bladder_empty) {i.bladder = empty?};

\node[block, below of=bladder_empty] (execution_block_2) { i.close(bladder)\\
 i.close(trousers)\\
 i.flush(urinal)
 };

\node [block, below of=execution_block_2] (exit) { i.exit() };

% The connections
\path [line] (business) -- (person);
\path [line] (person) -- (sex);
\path [line] (execution_block_1) -- (open_bladder);
\path [line] (execution_block_2) -- (exit);

\path [line] (sex) -- node [near start] {no} (sex2);
\path [line] (sex) -| node [near start] {yes} (execution_block_1);
\path [line] (sex2) -- node [near start] {no} (execution_block_1);
\path [line] (sex2) |- node [near start] {yes} (exit);
\path [line] (open_bladder) -- (bladder_empty);
\path [line] (bladder_empty) -- node [near start] {yes} (execution_block_2);
\path [line] (bladder_empty) -- +(4,0) -- +(4,3) -- node [near start] {no} (open_bladder);
\end{tikzpicture}

\end{document}

The decision block with the bladder emptiness check has more than one curve. -| or |- didn’t work so the trick here is that you have to add coordinates (x,y) to the connection line where it should curve.

jQuery injection using Firebug?

slopjong — Sat, 27 Mar 2010 11:47:34 +0000

A new day, a new question.

I was trying to load a json object while using Firebug and jQuerify to inject jQuery code into the website of the currently active tab. If you don’t know what I’m talking about, these are firefox add-ons. Firebug is a great debugging tool whereas jQuerify adds the jQuery library to any website if it’s not yet loaded.

Now some details to my recent problem. If I enter the URL into the browsers location field I get a proper json object back. If I send an XMLHttpRequest to the same URL the server responses with the status code 301 Moved Permanently. Has this issue to do with the Same Origin Policy (SOP) ?

If so I need a workaround because this URL will be the new API URL for some web apps.

Any suggestions what this could be?

Edit:
It wasn’t a SOP problem but I also had to face with such a problem later. The above described behaviour came from a missing / at the end of the URL. Entering such a URL into the location field the browser automatically add the tailing slash if it’s missing. After I found that out I wasn’t able to fetch the json from another domain. It’s been months that I’ve been coding jQuery a lot so I forgot one little but important information. The server has to send an additional header to allow other domains. More about this later in a seperate post.

svn2web

slopjong — Tue, 02 Mar 2010 11:20:42 +0000

svn2web is a subversion hook script that uploads the committed files to a server by the ftp or sftp protocol. With this script it’s very easy to keep your local development branch of your web project synchronized with your server as long as you don’t make server-side changes.

Be aware that you complete the PATH variable as the script isn’t executed in an interactive shell. This means no .bashrc or .profile are read. So you have to set PATH by yourself. You also have to pay attention to the order of the binary locations. I had some trouble with the Leopard¹ svn installation and the macports installation. The former was an older version which couldn’t work with repository created by the latter.

If you get one of these error messages

svnlook expected fs format '2'; found format '4'

Invalid change kind in rev file

take a look at the PATH before you start debugging svn2web

For those who want to set ftp/sftp options you can do this by setting the svn property svn2web-options. Unfortunately this is nowhere documented so if it’s not working properly you should contact the dev team or fix it by yourself. Don’t forget to spread the bugfix with the world.

The cat I got from the Apple zoo ↩

How to use BackPress?

slopjong — Sun, 21 Feb 2010 17:56:58 +0000

For my recent project I want to use some WordPress core functions but it’s too disproportionate to install the full system. Then I found BackPress which is exactly what I need. It’s a collection of WordPress, bbPress and GlotPress libraries.

The usage of this library collection requires some work. In fact you only need to include functions.core.php and the libraries you need. But to find out what files you exactly need can be hard because some functions have a lot of dependencies so my proposal is to include everything as you needn’t to care about any dependencies later on.

Furthermore some files have to be included exclusive-or what means that either the one has to be included or the other one. Download backpress.php and include the extracted file in your web project.

Facebook Lite

slopjong — Sat, 13 Feb 2010 18:54:06 +0000

I wrote a script for minimizing the facebook theme. For this you need the Greasemonkey firefox add-on.

To install the script click on this link Facebook Lite