Tag Archive for 'linux'

Adventures in Vector Quantization

Published on 01/08/2011 in Tutorials. 0 Comments Tags: cinepak, comprsesion, ffmpeg, linux, mencoder, question, Ubuntu, vqa.

Ever since seeing Radio Dada by Rosa Menkman I’ve been forever trying to reproduce the style of compression/glitches it uses.

In my limited knowledge about the production of the video I do know what it uses compression artifacts found in the Cinepak codec. So, I set out to try and find a way of converting a video to a video that uses the Cinepak codec. If you’ve been following me you’ll that I’ve asked for help on many fora and mailing lists for help with initially little success.

Hidden somewhere in the documentation for MEncoder is a page detailing how to use Windows codecs on Linux for encoding. The copy of the Cinepak codec (iccvid.dll) that came with MEncoder/medibuntu was a bit broken so I had to use Google to download a new version.

Once I had that I used MEncoder to convert a video to an avi with the Cinepak codec. (I’m using mencoder version 2:1.0~svn33951~natty):

mencoder infile.avi -ovc vfw -xvfwopts codec=iccvid.dll -oac mp3lame -o outfile.avi

Unfortunately for me this did not produce the compression artifacts that I was after. I tried reencoding the video using the Cinepak codec several times but this only just made the video darker:

(Original video)

Also, my attempt to encode the video using the Cinepak codec but with a low bitrate didn’t work as, at least when using MEncoder, the codec doesn’t have any encoding options. Drats! With that said, if anyone knows of a way of encoding using Cinepak with low/different bitrates on Linux using only freely available/open source software please do let me/the world know.

After this I felt very disheartened until I did a little bit of digging into the actual codec. I discovered that this codec is one of a few is based on Vector Quantization. I don’t know much about this but I felt that this must be the key. The video codecs that are based on Vector Quantization are Sorenson, Indeo and VQA.

I had no luck finding a way of converting to Sorenson and Indeo. However, I’ve had more luck with VQA. Wikipedia has a bit of information on the codec:

Vector Quantized Animation, known by its acronym VQA is a file format originally developed by Westwood Studios for video encoding in their game The Legend of Kyrandia and monopoly.

If you ever came across a Sega Saturn you probably will have come across videos encoded using VQA. As that Wikipedia article states, apart from the one used by Westwood Studios, only one VQA encoder exists. VQA Encoder v0.5 beta 2 by ugordan is the only known VQA encoder and luckily it works perfectly using Wine (I’m using version 1.2.3-0ubuntu1~ppa1) on Ubuntu 11.04. You’ll have to download some additional DLLs. Just do some research to find out which ones.

In order to use the software you need to convert your video to image files. I’ve had luck with converting the video to PCX files using FFMPEG:

ffmpeg -i infile.avi -sameq outfile_%03d.pcx

Then, in the VQA Encoder v0.5 beta 2 copy these options:

VQA encoder options

The program will automatically recognise that there are many images in the folder. After encoding has finished you should have a file called out_.vqa. In FFMPEG execute:

ffmpeg -i out_.vqa -sameq outfile.avi

You should now have a video that has similar compression to the Cinepak codec used with low bitrates:

(Original video)

Brilliant! Well, not so brilliant. The problems with using this software are the following:

The software is no long being updated
Because of this it could stop working at any time and no support would be offered
It can only output video at 640×400, which you can see by the way it crops the video
It isn’t open source, though that only matters if you exclusively use open source software

So, is there any other way to achieve these compression artifacts, preferably using open source software?

What Glitch? scripts

Published on 11/03/2011 in Art and Tutorials. 5 Comments Tags: batch, databend, glitch, linux, scripts.

For the What is Your Glitch? videos I wanted to build up on some of the extensive work that has already gone into the documentation, deconstruction and glitching of file formats. Rosa Menkman has already done a great job of documenting some of the more well-known file format glitches in the Vernacular of File Formats, which I recommend you all read. For this exercise I wanted to explore some of the more obscure file formats. Using open source software and Ubuntu has given me access to a wealth of programs that can still generate obscure file formats, such as pcx, pix and sgi. Through these experiments I also found inconsistencies in the way that different programs generate files, which is evident through my decision to use GIMP to convert files rather than Imagemagick in some of the scripts. Enough chit-chat, download the scripts!

Code hosted on GitHub

The method of glitching used in most of the scripts is the much-documented find and replace method. If you take a look in the scripts – and I encourage you to do so – you can change the characters that are being searched for and replaced. I’ve simply chosen characters that are sure to get results and are less likely to completely destroy the file.

Required Dependencies

Each script has its own set of dependencies, but to ensure you can run each one you’ll need the following:

Sed
GIMP – I use 2.71 beta available for Ubuntu from this ppa. Other versions remain untested
Imagemagick
GlitchSVG
FFMPEG
Mplayer
WebP

Basic Usage

1. Make the file executable: In a terminal type chmod+x [name of script] (e.g. what_glitch_webp.sh)
2. Run ./what_glitch_webp.sh in a terminal window
3. Drop a video file into terminal window and press Enter
4. Get a cup of tea

Notes

The scripts have only been tested on Ubuntu 10.10. If you are able to get them working with other operating systems please feel free to share your techniques
These scripts seem to work best with avi video files that are 24 or 25 frames per second. Files that are 30 frames per second get out of sync with the audio
Make sure the name of the directory containing the video to glitch doesn’t contain spaces e.g. “untitled_folder” instead of “untitled folder”
The video needs audio order for this script to work. If you know what you’re doing you can edit parts of this script for it to work on files that have no audio
As these scripts processes each frame of a video file it will take a very long time to complete. It is recommended for use only on small video clips!

These scripts by no means even begin to cover all of the image file formats available. There were a few formats that were not as easy to batch-process or were simply too large to process, such as xpm and xbm. For these you’ll have to do it manually or explore other ways of batch processing. They’re also not the most efficient of scripts. Some way into processing 400 video frames the script would slow down a lot. I welcome any bug fixes or suggestions on fixing this

There’s still plenty of undiscovered glitches out there in the wild just waiting to be hunted down and exploited. I encourage anyone, everyone and their mother to pick from this long, but by no means complete list of image file formats and to find a way to glitch them!

Echobender

Published on 01/02/2010 in Art. 0 Comments Tags: code, databend, glitch, imagemagick, linux, script, shell, sox, Ubuntu.

Myself and Mez recently finished a script called Echobender that automatically databends images.

Click to download

To use it you’ll need:

A computer with Linux installed. I don’t have a Windows or Mac PC so I can’t test it on those
Sox. On Ubuntu you can install it via sudo apt-get install sox
Convert, which is part of ImageMagick. On Ubuntu you can install it via sudo apt-get install imagemagick

Once you have those installed just execute ./echobender.sh from the terminal and then drop a .jpg or .bmp file into it. The output will be in a folder called “echo”.

If you look closely at the script you can see a way to convert any data into an image! I’ll leave that one up to you… Here’s the source code for all those interested:

#!/bin/sh -e
# Echobender
# By Antonio Roberts and Martin Meredith
# www.hellocatfood.com | www.sourceguru.net
# GNU/GPL

segons=`(date "+%Y%m%d%H%M%S")`
outfile="${segons}"

if [ ! -d ./echo ]; then
	mkdir ./echo
fi
clear
echo -e "\033[31m---------------------------------------------------- \033[0m"
echo -e "\033[33m Echobender \033[0m"
echo -e "\033[32m---------------------------------------------------- \033[0m"
echo -e "\033[35m---------------------------------------------------- \033[0m"
read -p "DROP A FILE HERE> " foo
echo -e "\033[32mLets bend $foo \033[0m"
echo -e "\033[35m---------------------------------------------------- \033[0m"
foo="$(echo $foo | sed -e "s/'//" | sed -e "s/'//")"
bn=$(basename $foo | sed -e 's/\.[a-zA-Z0-9]*$//')
imsize=$(identify -format "%wx%h" $foo)
cp $foo ./echo
convert ./echo/${bn}.* ./echo/${bn}.bmp
cp ./echo/${bn}.bmp ./echo/${bn}.raw
sox -r 482170 -e u-law ./echo/${bn}.raw ./echo/${bn}2.raw echo 0.8 0.9 5000 0.3 1800 0.25
convert -size $imsize -depth 8 rgb:./echo/${bn}2.raw ./echo/${bn}.$outfile.bmp
rm ./echo/${bn}.raw ./echo/${bn}2.raw ./echo/${bn}.bmp ./echo/${bn}.jpg
echo -e "\033[33mJob done. Check ./echo \033[0m"
echo -e "\033[31m---------------------------------------------------- \033[0m"

Thanks to Imbecil‘s MPegFucker script for much of the inspiration.

Databending using Audacity

Published on 16/11/2009 in Tutorials. 18 Comments Tags: abstract, Audacity, data, databending, experimentation, File format, Filename extension, glitch, Graphics, Image file formats, linux, osx, Ubuntu, windows.

Thanks to some help on the Audacity forum I finally know out how to use Audacity to databend. Previously I’d been using mhWavEdit, which has its limitations and just doesn’t feel as familiar as Audacity. From talk on the various databending discussion boards I found that people would often use tools like Cool Edit/Adobe Audition for their bends. Being on Linux and restricting myself to things that run natively (i.e. not under Wine) presented a new challenge. Part of my task was to replicate the methods others have found but under Linux. My ongoing quest is to find things that only Linux can do, which I’m sure I’ll find when I eventually figure out how to pipe data through one program into another!

Here’s some of my current results using Audacity:

Just so you don’t have to go trawling through the posts on the Audacity forum here’s how it’s done. It’s worth noting that this was on using Audacity 1.3.12-2 on Linux. Versions on other operating systems may be different. Before I show you this it’s probably better if you work with an uncompressed image format, such as .bmp or .tif. As jpgs are compressed data there’s always more chance of completely breaking a picture, rather than bending it. So, open up GIMP/your faviourite image editor and convert it to an uncompressed format. I’ll be using this picture I took at a Telepaphe gig awhile back

Next, download Audacity. You don’t need the lame plugin as we wont be exporting to mp3, though grab it if you plan to use it for that feature in the future. Once you have it open go to File > Import > Raw Data and choose your file. What you’ll now be presented is with options on how to import this raw data, which is where I would usually fall flat.

Import Raw Data

Under Encoding you’ll need to select either U-Law or A-Law (remember which one you choose). When you choose any other format you’ll be converting the data into that format. Whilst you want to achieve data modification this is bad because it’ll convert the header of the image file, thereby breaking the image. U/A-Law just imports the data. The other settings do have significance but I wont go into that here. When you’re ready press Import and you’ll see your image as data!

Image as sound

Press play if you dare, but I’d place money on the fact that it’ll probably sound like either white noise or ~~Aphex Twin~~ glitchy goodness. This is where the fun can begin. For this tutorial select everything from about five seconds into the audio. The reason for this is because, just like editing an image in a text editor, the header is at the beginning of the file. Unless you know the size of the header and exactly where it ends (which you can find out with a bit of research), you can usually guess that it’s about a few seconds into the audio. The best way to find it out is to try it out!

Anyway, highlight that section and then go to Effect > Echo

Apply the echo

Leave the default settings as they are and press OK

You’ll see that your audio has changed visually. It still wont sound any better but the magic happens when you export it back to an image file, which is the next step.

Once you’re happy with your modifications go to File > Export. Choose a new location for your image and type in the proposed new file name but don’t press save just yet. You’ll need to change the export settings to match the import settings.

Change the file format to Other Uncompressed Files and then click on the Options button.

Export settings

Change the settings to match the ones above (or to A-Law if you imported as A-Law). With that now all set you can now press Save! If you entered a file extension when you were choosing a file name you’ll get a warning about the file extension being incorrect, but you can ignore it and press Yes. If you didn’t choose a file extension, when the file is finished exporting, add the appropriate extension to the file. In my case I’d be adding .bmp to the end.

Here’s the finished image:

Freaky!

There’s of course so many different filters available in Audacity, so try each of them out! If you’re feeling really adventurous try importing two or more different images and then exporting them as a single image.

Comments on this post are now closed. If you need help on this try the Audacity forum