Author Archives: Johannes Sasongko

Transliterating arbitrary text into Latin script

This post explores one of the capabilities of the PyICU library, namely its text transformation module. Specifically, we’ll look at the simplest use case: transliterating text into Latin script.

Say you are given a list of phrases, names, titles, whatever, in a script that you can’t read. You want to be able to differentiate them, but how, when they all look like random lines and curves? Well, let’s turn them into Latin characters!

>>> import icu
>>> tr = icu.Transliterator.createInstance('Any-Latin; Title').transliterate
>>> tr('Ἀριστοτέλης, Πλάτων, Σωκράτης')
'Aristotélēs, Plátōn, Sōkrátēs'

There we go. Even if you still can’t pronounce these names correctly, at least they’re hopefully easier to recognise because they are now in a script that you are more used to reading (unless you’re Greek, of course).

'Any-Latin; Title' means we want to transliterate from any script to Latin, then convert it to title case. If that’s too simple, the ICU documentation has the gory details of all the supported transforms.

Easy, no?

Caveats

Do not rely on the output as pronunciation guide unless you know what you’re doing. For example, the Korean character 꽃 is transliterated by ICU as kkoch to keep it reversible, even though the word certainly does not sound like the gunmaker’s nor Kochie’s last names, and definitely not like the synonym for rooster (the modern romanisation, which matches closer to the correct pronunciation, is kkot).

The transliteration of Han characters (shared between Chinese, Japanese, and Korean) uses Chinese Pinyin, and thus may not resemble the Japanese and Korean romanisations at all. This makes the transliteration of many Japanese texts particularly awful.

>>> tr('日本国')  # "Nippon-koku" = Japan
'Rì Běn Guó'

Oops, that could start an Internet war. Use a different library if you are primarily dealing with Japanese text.

Another unfortunate thing with ICU is that there are still scripts that it doesn’t support at all. For example, it can’t transliterate to/from Javanese.

>>> tr('ꦫꦩꦏꦮꦸꦭꦲꦶꦁꦱ꧀ꦮꦂꦒ')
'ꦫꦩꦏꦮꦸꦭꦲꦶꦁꦱ꧀ꦮꦂꦒ'

Maybe one day.

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Using GitLab’s CI server

GitLab provides a continuous integration server, which is pretty nice for building, testing, and packaging your software and having all the UI integrated in GitLab. If you’re just using the free GitLab.com hosting, you get to utilise their Docker-based runner. (If your build process requires a non-Linux OS you’ll have to provide your own runner.)

Getting a basic build up and running is pretty simple. For example, here’s one job named test that only runs make check:

test:
  script:
    - make check

If your test suite can measure code coverage, GitLab can also show it in the UI. At the moment this feature is rather rudimentary and requires you to go to the project settings and enter a regular expression to find the coverage amount in the build output.

The following is an example that works with coverage.py when you only have a single Python file. I haven’t tried it with multiple files; it may require a wrapper script that calculates the total coverage amount.

test:
  image: python:3-alpine
  script:
    - pip install coverage
    - coverage run foo.py
    - coverage report -m

# Regex that matches the coverage amount:
# ^\S+\.py\s+\d+\s+\d+\s+(\d+\%)

A few lessons learnt from setting up test hooks for a small Python app:

  • There is no way to test changes to your build script without pushing a commit. And then the build results will stay in your project page forever with no way to clean up the irrelevant ones. You can run builds locally with gitlab-runner, e.g. gitlab-runner exec shell test to run the test job on the local shell (replace shell with docker to use Docker). (Thanks Evan Felix for the info about gitlab-runner.)
  • GitLab.com’s default Docker image (ruby:2.1 at the time of writing) is really fast to spin up, possibly because it’s cached. However, you should still explicitly name a Docker image in case the default changes.
  • Installing packages is slower than downloading a Docker image. It’s not worth going out of your way to use the default image if you then have to call apt-get. Try to find a pre-built Docker image that has all the packages you need instead. However, we’re talking about differences of about ten seconds, so just choose the image that is most convenient.
  • The ruby:2.1 image has Python 2 but not Python 3.
  • Docker’s Python repository lists a number of Alpine-based images. As you would expect, these are smaller and slightly faster to download than the other (Debian-based) images.
  • The coverage regex requires the percent sign to be escaped (\%).

The Moodbar audio visualisation method

One of the niftiest legacies of the old Amarok music player (version 1) is the Moodbar visualisation method. The idea behind it is simple: take the source audio signal, analyse it, and create a colourful representation of the sound as a timeline.

[Image showing Exaile with Moodbar visualisation, in which the original seek bar is replaced by a colourful-looking bar]

Exaile with Moodbar replacing the standard seek bar

Back in 2009, Solyanov Michael created an external plugin to add Moodbar support to Exaile, and at some point it was imported into the Exaile tree. Now that we’re upgrading Exaile to GTK+ 3, I have been rewriting the plugin’s UI code to use Cairo instead of GDK drawing functions, which don’t exist anymore. (Unfortunately I don’t think I’ll have the time and motivation to implement all features of the existing plugin.) The above screenshot shows a sneak peek of how the new UI currently looks like.

What do the colours mean?

Moodbar is explained in a 2005 paper by Gavin Wood and Simon O’Keefe, which presents a number of algorithms for visualising audio signals. Specifically, the Bandwise Spectral Magnitude method is the one implemented as Moodbar.

Long story short, for each point in the timeline, the red channel represents low frequencies, green represents mid frequencies, and blue represents high frequencies. In practice, however, it is often difficult to imagine what an audio segment will sound like just based on its colour. The only thing you can pretty accurately guess is the audio level based on colour intensity (bright=loud, dark=quiet).

I’ve prepared a few Moodbar examples with playable audio for you to see this in action. Some of the samples (Hypocrisy, What Is Love) are pretty good and show all sorts of colours differentiating song sections. Some are less exciting, either because the song mostly uses a single instrument (Spring) or because the song is relatively monotonous (Max).

Current support in media players

To my knowledge, there are only three actively-developed media players with Moodbar support, all of which are based on Amarok 1 to some degree: Exaile, Amarok 2, and Clementine. Ironically, Amarok 2’s Moodbar support is the least integrated; you need to manually scan your files, whereas Exaile and Clementine do this for you as they play individual files.

Currently Exaile and Amarok 2 still rely on the old, GStreamer 0.10-based Moodbar program. Clementine seems to have integrated Moodbar into their own code and is using it as a library. Their latest release is still using GStreamer 0.10, but their development tree already contains a GStreamer 1.x-based Moodbar.

Future

Right now we are focusing on finishing the GTK+ 3 port of Exaile, which includes getting the Moodbar plugin to a reasonable state. The basic Moodbar functionality is ready; I just have to implement a fallback UI for tracks that have not been or cannot be scanned for whatever reason.

Other Moodbar-related tasks on my radar (read: may or may not happen):

  • Steal split Clementine’s new Moodbar code into a separate library so that Exaile and other media players can make use of it. I have the code sitting ready to be published, but it still needs more testing, especially since I’ve just found out that it produces different output to the original Moodbar program.
  • Add some of the old features that don’t make the cut to the GTK+ 3 port (darken should be doable; waveform will be tricky, given the way the new drawing is done).
  • Add support to share the Moodbar cache with Clementine. Not terribly useful, to be honest.
  • Do more research to find a better timeline visualisation method.

Christoph Gohlke won a PSF Community Service Award in 2014 (and it went unnoticed)

In October 2014, Christoph Gohlke won a Python Software Foundation’s Community Service Award. Gohlke is the (sole?) maintainer of the most impressive collection of Windows binaries of Python extensions, and his website is often the only place to find Win64 builds of some libraries.

Despite his significant contribution, the award seems to have gone unnoticed. No official announcement, no news articles, no written acknowledgement of what he did that warranted the award. It’s not even listed in the PSF Community Service Awards page, which seems to have stopped being updated one year ago (update: this is fixed now).

I’m no management expert, but this looks bad on the PSF. The point of giving an award is not just to make the recipient feel good and continue what they’re doing, but also to encourage others to contribute to the award-giver’s interests. In this case, the first seems to have been cheapened, and the second is not accomplished at all.

CMake’s ugly programming language

I’ve just discovered Rosetta Code not long ago, and found it quite fun to browse around. It shows you the code for various programming tasks in different programming languages. While looking at the Quicksort page, I noticed that it didn’t have a CMake version, so I decided to try writing one.

function (quicksort array_var)
    set (array ${${array_var}})
    if ("${array}" STREQUAL "")
        return ()
    endif ()

    set (less)
    set (equal)
    set (greater)
    list (GET array 0 pivot)

    foreach (x ${array})
        if (x LESS pivot)
            list (APPEND less "${x}")
        elseif (x EQUAL pivot)
            list (APPEND equal "${x}")
        else ()
            list (APPEND greater "${x}")
        endif ()
    endforeach ()

    set (array)
    if (NOT less STREQUAL "")
        quicksort (less)
        list (APPEND array ${less})
    endif ()
    list (APPEND array ${equal})
    if (NOT greater STREQUAL "")
        quicksort (greater)
        list (APPEND array ${greater})
    endif ()
    set ("${array_var}" ${array} PARENT_SCOPE)
endfunction ()

set (a 4 65 2 -31 0 99 83 782 1)
quicksort (a)
message ("${a}")

I’ve worked with CMake for years, and I think it’s a good build system, but I really wish it had switched to a saner language. The CMake language is actually pretty simple and consistent at the syntax level: everything is in the form command(string), where the string syntax is slightly confusing but still rather understandable once you’ve figured out the quoting and variable expansion mechanisms. It’s how that string argument is used that can be messy, inconsistent, and ambiguous. Effectively, it’s as if every command had its own syntax.

Around 2008, there was an experiment to allow writing CMake scripts in Lua. The project never caught on and was abandoned. I think part of the reason was that the thread discussing it in Lua’s mailing list was single-handedly derailed into pointless bickering (which reminds me of the “poisonous people” talk).

CMake is stuck with a mediocre programming language for the foreseeable future. It’s not as bad as it sounds, though. The simplicity of the syntax has its advantages, and writing CMake buildfiles rarely gets frustrating. It would make a terrible general programming language, but as a build system scripting language it’s workable.

Authorisation UIs: design issues and going towards fixing them in Wayland

I was browsing the xfce4-dev mailing list when I stumbled on a request for comment by Steve Dodier-Lazaro (who I knew in the past through the #exaile IRC room) on his article regarding the design of authorisation UIs.

The article covers a lot of ground, from current issues plaguing these UIs (in Windows UAC dialog, gksu, etc.), to the types of operations in Wayland that are planned to require authorisation, to brainstorming ideas for moving forward. A lot of issues are still unsolved and I suspect will be years away from being solved, but I’m glad that people are talking about them. The article also calls for further academic research on fixing these issues.

Exaile dropping the 0.x versioning

The next version of Exaile, which was to be version 0.3.3, will be version 3.3.0. We feel that the 0.x versioning was more confusing than actually useful or representative of the development process; in addition, the new versioning avoids long version numbers like 0.3.2.1.

In related news, Exaile 3.3.0 is going to be released soon. The RC is already out; please help us test it and iron out last-minute bugs.