I currently blog at several other places


https://searchvoidstar.tumblr.com (programming)
https://videomeltdown.tumblr.com (glitch art)
https://github.com/cmdcolin (github)
https://twitter.com/cmdcolin


Feel free to visit or follow/say hi

chaotic pendulum

way to go blogger

glitchdrone

experiment with raw video codecs and synth track

prefast code analyze

Visual C++ has a static code analyzer called PREfast that ist now ditributes in the new-ish Windows SDK v6.1. PREfast analyze used to be distributed in the DDK, and it used in part by the Microsoft Secure Development Lifecycle (SDL). The analysis basically catches stuff you forget when you're dealing with a lot of code

- Checking for NULL pointers or parameters in your functions
- Out of bounds indexing or buffer overflows for example in array indexes in 'for' loops
- Local variable scope masking other scopes

To make code analyze work with visual studio, for example VS2005, I set up this batch file

; devenv-prefast.bat
call "C:\Program Files\Windows SDK\v6.1\vcvars32.bat"
start "C:\Program Files\Microsoft Visual Studio 8.0\VC\Common7\IDE\devenv.exe" /UseEnv

This uses the PATH, INCLUDES, and LIBS from vcvars32.bat, and uses them in the Visual Studio environment. Then, you add /analyze to the Project -> C/C++ Command line options and it does the static code analysis

dotfiles

Everyone knows linux stuff is totally customizable -- but what I figured out was that a lot of the configuration options are in hidden 'dotfiles'! I wanted to give cygwin a dark theme, so here's the most basic dark theme for vim and xterm

vim using .vimrc

" Example .vimrc here http://www.vi-improved.org/vimrc.php
" Vim colorschemes generator http://inspiration.sweyla.com/code/
" {
set background=dark " we plan to use a dark background
colorscheme inspiration907827
syntax on " syntax highlighting on
" }

xterm using .Xdefaults

XTerm*Background: black
XTerm*Foreground: grey
XTerm*utf8: 1

-- check out http://dotfiles.org/ for more of this stuff

opengl post processing

I figured out how to use OpenGL for post processing ... finally -- sort of used it as an excuse for valentines day to make something that would run on a Mac



Uses this pixel shader to make the big pixel convolution - http://www.lighthouse3d.com/opengl/ledshader/

wtl for the poor

I've always liked WTL. I learned programming by exploring Windows programming and C++ -- For me, just using the "Win32 API" was a good exercise (was it really though?). As I got better, I was constantly using C++ in weird ways, but when WTL came out, I knew that that it was actually good C++ for the Windows programming


WTL project circa 2006 - http://zxcvbn.googlecode.com/svn/trunk/wtltrip/

Recently though, Microsoft made WTL not so free, by taking rid of the MFC/ATL in the "Platform SDK" (which is now called the "Microsoft SDK").

The SDK does not have ATL base classes anymore, and it does not come with the Visual Studio Express Editions either. Free open source web browser Google Chrome uses WTL on Windows, and has some extensive workarounds for the issues


I found that I could get the ATL base classes if I register with MSDN and download the WDK here ...wait what? the device driver development kit? Microsoft acknowledges this in the WDK release notes : Windows Driver Kit (WDK) Version 7.0.0 Release Notes

[August 2009] ATL Best Practice - Use the Visual Studio release

ATL is included in the WDK as a convenience for driver developers who need to create Windows applets for their drivers. ATL should not be used for software development beyond this scope. The ATL that is available through Visual Studio provides a more complete and current set of libraries and should be used for development of software and web applications. Visual C++ Express Edition is available for free from MSDN.

So there aren't any good free sources for the MFC/ATL base, so the WTL is no longer a free software platform like it should be.

sources:
http://www.caloni.com.br/blog/archives/como-usar-wtl-com-o-atl-do-ddk

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last.fm 2009

Last.fm has a cool API that let's you gewt almost any sort of data from them just using a web request in XML or JSON format. During their countdown for the top artists of 2009 they encouraged people to use the API, and I used the Last.fm API to show how many plays you scrobbled from each artist in the top 40.

http://zxcvbn.t35.com/lastfm-2009.html

Features:

• Uses Last.fm API to get JSON data for number of songs listened to
  
• Dynamic page effect using JavaScript to organize page elements
  
• Uses last.fm javascript client API
  

The program is pretty simple, it uses the Library.getTracks API method to retrieve your listening data. I create a last.fm object. you need an 'API key' and 'API secret', which you 'apply' for on their API page http://www.last.fm/api. Then, you can call any of the methods of the API you like

Using my program as an example

/* Create last.fm object */
var lastfm = new LastFM(
{
apiKey: 'Apply for key at http://www.last.fm/api',
apiSecret: 'Apply for API code at http://www.last.fm/api',
cache: cache
});

/* Success function parses JSON data. note: stringify JSON data before parsing */
function success(json_data) {
var json_string = JSON.stringify(json_data);
var json_parse = JSON.parse(json_string);
var tracks = json_parse.tracks;
}

/* Failure function parses error codes */
function failure(code, message) {
alert(code + ': ' + message);
}

/* Call the api function with JSON format API parameters */
lastfm.library.getTracks({ user: "LastFM Username", artist: "Britney Spears" },
success_function_callback, failure_function_callback);

Update:
I made it so you can find out how many songs you've listened to by any artist you type in. It's not very easy to find out if the artist isn't in your top charts

http://zxcvbn.t35.com/lastfm-2009.html

cpu post processing

Out of curiosity, I tried to replicate the post processing effect using the CPU instead of using shaders on the GPU. This is complicated because we're not supposed to access the graphics data directly, but uh-hmm -- whatever

To get the rendered graphics data, I use GetRenderTextureData which uses the system memory pool. But MSDN says that : "system memory is not typically accessible by the Direct3D device". So we must wait on a lock to copy from the system memory to default memory. This is a really costly operation and basically is the failure of my experiment. Running in exclusive (fullscreen) mode, takes about ~50ms to run, and the framerate is killed to <20fps

// Texture surfaces with given CreateTexture parameters
// renderTexture is D3DUSAGE_RENDERTARGET, D3DPOOL_DEFAULT
// systemMemTexture is D3DUSAGE_DYNAMIC, D3DPOOL_SYSTEMMEM
// defaultMemTexture is D3DUSAGE_DYNAMIC, D3DPOOL_DEFAULT

pd3dDevice->GetRenderTargetData(renderTextureSurface, systemMemSurface);
systemMemSurface->LockRect(&source, NULL, 0);
defaultMemSurface->LockRect(&dest, NULL, 0);
copy(source.pBits, dest.pBits);
systemMemSurface->UnlockRect();
defaultMemSurface->UnlockRect();

Apparently, GPGPU programming is enabled by hardware and the software. For example in nVidia CUDA it let's programmers control shared memory for hardware the graphics that enables programmer control (see Toms's Hardware: CUDA from the Hardware Point of View )



From the GPGPU FAQ it says about the shared memory

"Texture read operations are routed through a cache structure to allow efficient exploitation of reference locality. Read operations also factor into shader thread scheduling as read operations that miss the cache will block the thread and cause other ready threads to run while waiting for the read to memory to complete. Writes are routed through different logic that does some amount of buffering to maximize the efficieny of writes."

gpu post-processing

I wanted to explain an overview of the post-processing effects using GPU shader programs since I've been working on this for awhile now. Basically, the rendering for post processing is broken into two steps

- we render-to-texture using normal rendering routines
- then use a pixel shader to texture a square with the render-target texture

The code I used the DirectX SDK sample ($SDK\Samples\C++\Direct3D\PostProcess)
Here is a simple model of the rendering

// render-to-texture
graphics->SetRenderTarget( offscreenTexture );
graphics->RenderScene( );

// square is the size of the screen, from back buffer description
VERTEX quad [4] = /* use the BackBufferDescription( ); */

// set shader parameters
shader->SetTechnique( "RenderPostProcess" );
shader->SetTexture( “offscreen_texture", offscreenTexture );

// square is textured by the pixel shader effect
graphics->SetRenderTarget( screen );
graphics->DrawPrimitive( quad );

I based this code off of the DirectX SDK sample ($SDK\Samples\C++\Direct3D\PostProcess, definitely look at that this if you are trying this). The square is calculated to fit the screen (using DXUTGetD3D9BackBufferSurfaceDesc). Then we texture the "fullscreen square" using our RTT texture, and we can use pixel shader effects during this rendering.

Here, the simplest "toon shader" ever

// render target from effect->settexture
texture offscreen_texture;
sampler2D s = sampler_state {
 Texture = <>;
};

// "toon shader"
float4 PostProcessPixel(float2 uv : TEXCOORD0) : COLOR
{
 float4 c = tex2D(s, uv_coord);
 c.rgba -= (Color.rgba % 0.3f );
 return c;
}

technique RenderPostProcess {
 pass p0 {
   VertexShader = null;
   PixelShader = compile ps_2_0 PostProcessPixel ();
   ZEnable = false;
 }
}

Thanks to gamedev for helping me with this miracle



Updated:

Source code - http://zxcvbn.googlecode.com/svn/trunk/skelly/
Wiki page - http://code.google.com/p/zxcvbn/wiki/skelly
Demo - http://zxcvbn.googlecode.com/files/Skelly.exe

graphics pipeline

It's important to know how shaders work with the graphics pipeline, because the "shader model" of graphics programming is totally different from the "fixed function model"! MSDN says here http://msdn.microsoft.com/en-us/library/ms800169.aspx

"The following user-mode display driver functions are not called by the Direct3D runtime when the vertex shader is enabled

• * MultiplyTransform
• * SetTransform
• * SetMaterial
• * SetLight
• * CreateLight
• * DestroyLight

This means that when you use shaders, you have to compute lighting and transformations! DirectX will also ignore flags like D3DRS_LIGHTING and texture state flags when you use shaders. When you program using the shader model, your shader program has responsibilities!

Contrast the API for the fixed function model, which uses the D3D device functions, with the shader model, which is similar but passeses parameters to your shader effects through the shader interface

IDirect3DDevice9::SetTexture vs ID3DXEffect::SetTexture
IDirect3DDevice9::SetTransform vs ID3DXEffect::SetMatrix
IDirect3DDevice9::SetLight vs ID3DXEffect::SetValue

I'll go over the exact responsibilities of shaders in your program. The MSDN page on the graphics pipeline says has some really important things about this - http://msdn.microsoft.com/en-us/library/ee415715(VS.85).aspx and I will use this gamasutra article for base code - http://www.gamasutra.com/features/20030418/engel_02.shtml



1) "The vertex-shader (VS) stage processes vertices ... performing per-vertex operations such as transformations, morphing, skinning, and per-vertex lighting."

Therefore, the vertex shader is typically responsible for worldview transformations and also calculating light values. The vertex shader sets up a VS_OUTPUT struct that contains transformed vertex information that is rasterized and passed to the pixel shader. The vertex shader outputs a VS_OUTPUT structure

struct VS_OUTPUT
{
float4 Pos : POSITION;
float3 Light : TEXCOORD0;
float3 Norm : TEXCOORD1;
};

VS_OUTPUT VS(float4 Pos : POSITION, float3 Normal : NORMAL)
{
VS_OUTPUT Out = (VS_OUTPUT)0;
Out.Pos = mul(Pos, matWorldViewProj); // transform Position wrt worldview
Out.Light = vecLightDir; // output light vector
Out.Norm = normalize(mul(Normal, matWorld)); // transform normal wrt world
return Out;
}

2) "A pixel shader is a program that combines texture data, per-vertex values, and other data to produce per-pixel outputs...Pixel shader inputs are interpolated from the vertex attributes of the primitive being rasterized"

We basically receive a VS_OUTPUT from our vertex shader as our pixel shader input, but the vertex data is interpolated. We use the NORMAL value to calculate lighting in our pixel shader, because the NORMAL in our pixel shader is interpolated from the rasterizer for our little pixel! The pixel shader outputs is a RGBA

float4 PS(float3 Light: TEXCOORD0, float3 Norm : TEXCOORD1) : COLOR
{
float4 diffuse = { 1.0f, 0.0f, 0.0f, 1.0f};
float4 ambient = {0.1, 0.0, 0.0, 1.0};
return ambient + diffuse * saturate(dot(Light, Norm));
}

Note: The POSITION register is not valid in the pixel shader, we are using pixels and not 3D space, but we still use the NORMAL data for lighting. The rasterization stage that converts our vertex shader data into pixel shader data is interesting. See the wikipedia page is good http://en.wikipedia.org/wiki/rasterization

erasing linux passwords also

I actually forgot my root password on a debian linux, for real! I was actually able to reset the root password on my the linux also pretty easily. I had to boot into single user mode, by way of the grub command line, add the option (see in the picture where it says press e to edit? add this onto the end)

single init=/bin/bash

apparently, it skipped loading the operating system or something, gave me a root shell in single user mode, butthen I was getting the error 'Authentication token lock busy' trying to reset the password. presumably this was because it was read only, so in the bash shell entered

mount -o remount,rw /

this made gave me read-write and then I was able to I was then able to reset the password using the passwd program like normally. wow.

erasing windows passwords

I thought that to fix a windows computer if you've forgotten a password, you needed to like recover the sam file (using like a recovery disk) and crack the password hashes using a program, some complicated process! It turns out that it is actually very simple to just clear the password on the passworded account using a boot disk, without harming anything, using the offline nt password editor - http://pogostick.net/~pnh/ntpasswd/

you burn the boot disk image to a cd using nero or some other program, and the boot disk automatically detects hard drive partitions with windows installed, and the accounts on the computer, and erases the password on the given accounts. It has lots of automatic and default options and is absolutely easy to use, you just literally hit enter a couple times and it will erase the password for you to login to an admin account. too easy

xkcd lols

doctor fill

I set up emacs to run with the sml/nj for one of my classes, and it turns out for my sanity that emacs comes with this artificial intelligence psychotherapist named doctor fill. it's pretty funny -- here's some things it says

F: Maybe your life have something to do with this.
F: What makes you believe your life has nothing to do with this?
F: Can you elaborate on that?
F: Is it because of the people you hang around with that you are going through all this?
F: I would appreciate it if you would continue.
F: Go on, don't be afraid.
F: Is it because of problems at school that you say you say arghh?
F: My secretary will send you a bill.
F: Bye bye.

It's pretty funny, it just keeps asking you to explain your reasoning, which is pretty good if you're being irrational in the first place. If you want a pretty good personal psychotherapist you can download it here (http://ftp.gnu.org/pub/gnu/emacs/windows/)
get the bin, the barebin download you have to download the sources also so just get the bin. you can use the sml-mode if you create a site-start.el file in the emacs/site-start/ directory.. follow the instructions here http://www.smlnj.org/software.html.

also very newest version (23.1, 07/30/09) has M-x butterfly ... "Do you really want to unleash the powers of the butterfly? (yes or no)"

record last.fm radio with foobar

I found a weird applciation of some foobar components that allows you to record last.fm radio.

I posted about foo_lastfm_radio earlier, the component let's you not just stream, but sample from a playlist of like 4-8 songs on average. interestingly you can also copy this stream using the foo_converter component. the converter tool automatically comes with foobar. just select any number of songs in the playlist, and then use the converter utility to download the songs.



unfortunately, this method generates transcodes, because of the converter utility, but if you don't care very much about the quality, then this method works pretty well. unfortunently, you cannot use foo_fileops to 'copy' the file from the last.fm radio but there might be a way to copy the radio stream without transcoding it.

analog-to-digital

I have recently learned how to 'rip' cassettes and stuff to digital so I thought I'd share some tips. I used this technique to rip cassettes but you can defintiely take this advice for ripping vinyl, the procedure is the same, it's just the set up is different. anyways, here's what you need to get started

1) you should get one of these monster icables, or something that joins the rca->1/8'' for your line-in
2) you need 'exact audio copy' [1] to record the audio from the line-in and it helps create a 'cue sheet'
3) then cuetools [2] to split the wav into tracks using the cue sheet


so set it up so you have the cables running into your computers mic slot or line-in and run eac -> tools -> 'record wav'. you should be able to see levels, but if you can't try going into the volume control panel and go to properties -> recording controls and select the line-in checkbox



after you get the levels, just let it record the whole tape, both sides, and then select 'process wav'

in the 'process wav' tool, first delete the leading and ending silence, but not the silence on the tape though, just the silence that is recorded when the tape wasn't even playing. then you place the 'track start' and 'gap start' markers to create a 'cue sheet'. track changes are marked by 'silence' on the tape, and the silence is much easier to see if you use the spectral view instead of the waveform view (view -> spectral).



inserting track start markers generates track n index 1 and gap markers generate track n index 0. insert a track start at the beginning of the tape's first song, and change the first marker marked track 1 index 1 into track 1 index 0 (effectively making the beginning of the recording a pregap until the first song). I also make the end of the tape silence a whole track that I edit into the cue sheet as a postgap.

go through the whole tape and then you basically get a cue sheet that looks like this




tell eac to save this cue sheet and the open it in a text editor to make sure it's correct (sometimes it doesn't export the gaps correctly, or some of the gaps correctly! see [3] you might have to manually edit the cue sheet, the syntax is easy enough) after you have saved the cue sheet then load cuetools and use the default settings

audio output - wav
output style - gaps left out



this will generate all the tracks

Directory of C:\Music\Kites - 2007 - Deny 1\New

01.wav
02.wav
03.wav
04.wav
05.wav
06.wav
07.wav
08.wav
09.wav
CUESheet.cue

the final step is to tag the files and compress the wav. use either musicbrainz or foo_discogs to tag the files, and either foobar2000's converter utility or eac to compress the wav's.

my favorite way to do it is to load the cue sheet into foobar, select the cue sheet and tag it with the foo_discogs plugin, this writes the track metadata into the cue sheet, and then you can give the cue sheet to eac and it outputs the compressed files with properly formatted filenames!

I hope this can help you create proper rips of your music, either with your cassettes or your vinyl

corruption 2

corrupting every frame of a video movie and re-encoding it. source video is some video feedback with high-def digital camera, music is made from some fm synth effects

fractals

I got this book called 'chaos in wonderland' and decided to try out mathematica to create some of the fractals in the books. the fractals are 'dynamical systems' described by basically differential equations (x[n+1] can be thought of as a discrete form of dx) [1]

x[n+1] = sin(y[n]*a) + c*sin(y[n]*b)
y[n+1] = sin(x[n]*a) + d*sin(y[n]*b)

my first attempt at code

ListPlot[Table[
   xn = N[Sin[y*b] + c*Sin[x*b]];
   yn = N[Sin[x*a] + d*Sin[y*a]];
   {x = xn, y = yn},
{i, 0, 10000}]]

this worked great. but to create a more functional style of iterated programming, I use the nestlist function which creates a list {x, f(x), f(f(x)), ...}, however instead of the one parameter 'x', I have parameters {x, y}. to deal with this I have to pass nested lists that I flatted at the end

Iter[list_] :=
{
   {{x, y}} = list;
   xn = N[Sin[y*b] + c*Sin[x*b]];
   yn = N[Sin[x*a] + d*Sin[y*a]];
   {xn, yn}
}

FSystemsPlot[l_, ax_, bx_, cx_, dx_] :=
{
   a = ax; b = bx; c = cx; d = dx;
   list = NestList[Iter, {{0.1, 0.1}}, 10000];
   ListPlot[Flatten[list,1]]
}]

the book had a list interesting parameters for this system that created these graphs

http://img198.imageshack.us/g/image10jhh.png/