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• Can you explain how to understand what the 'iwconfig' command displays in Ubuntu-9.04?

  - by Shawn

  I'm having trouble making my wireless connection work, and I realized I don't really know how to use the tools I have, in this case, the iwconfig command in Ubuntu-9.04. Here is what I get: ***iwconfig*** - lo no wireless extensions. eth0 no wireless extensions. wmaster0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"Network" Mode:Managed Frequency:2.412 GHz Access Point: Not-Associated Tx-Power=20 dBm Retry min limit:7 RTS thr:off Fragment thr=2352 B Power Management:off Link Quality:0 Signal level:0 Noise level:0 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 vboxnet0 no wireless extensions. pan0 no wireless extensions. "Network" is the name of my wireless network, btw. But what does this all mean? How can this information help me aquire a working wireless connection? When I try associating a key using sudo iwconfig wlan0 key s:my_key I get the following error message: Error for wireless request "Set Encode" (8B2A) : SET failed on device wlan0 ; Invalid argument. I do have the right key though, so what's the problem?

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• Image Erosion for face detection in C#

  - by Chris Dobinson

  Hi, I'm trying to implement face detection in C#. I currently have a black + white outline of a photo with a face within it (Here). However i'm now trying to remove the noise and then dilate the image in order to improve reliability when i implement the detection. The method I have so far is here: unsafe public Image Process(Image input) { Bitmap bmp = (Bitmap)input; Bitmap bmpSrc = (Bitmap)input; BitmapData bmData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; int stride2 = bmData.Stride * 2; IntPtr Scan0 = bmData.Scan0; byte* p = (byte*)(void*)Scan0; int nOffset = stride - bmp.Width * 3; int nWidth = bmp.Width - 2; int nHeight = bmp.Height - 2; var w = bmp.Width; var h = bmp.Height; var rp = p; var empty = CompareEmptyColor; byte c, cm; int i = 0; // Erode every pixel for (int y = 0; y < h; y++) { for (int x = 0; x < w; x++, i++) { // Middle pixel cm = p[y * w + x]; if (cm == empty) { continue; } // Row 0 // Left pixel if (x - 2 > 0 && y - 2 > 0) { c = p[(y - 2) * w + (x - 2)]; if (c == empty) { continue; } } // Middle left pixel if (x - 1 > 0 && y - 2 > 0) { c = p[(y - 2) * w + (x - 1)]; if (c == empty) { continue; } } if (y - 2 > 0) { c = p[(y - 2) * w + x]; if (c == empty) { continue; } } if (x + 1 < w && y - 2 > 0) { c = p[(y - 2) * w + (x + 1)]; if (c == empty) { continue; } } if (x + 2 < w && y - 2 > 0) { c = p[(y - 2) * w + (x + 2)]; if (c == empty) { continue; } } // Row 1 // Left pixel if (x - 2 > 0 && y - 1 > 0) { c = p[(y - 1) * w + (x - 2)]; if (c == empty) { continue; } } if (x - 1 > 0 && y - 1 > 0) { c = p[(y - 1) * w + (x - 1)]; if (c == empty) { continue; } } if (y - 1 > 0) { c = p[(y - 1) * w + x]; if (c == empty) { continue; } } if (x + 1 < w && y - 1 > 0) { c = p[(y - 1) * w + (x + 1)]; if (c == empty) { continue; } } if (x + 2 < w && y - 1 > 0) { c = p[(y - 1) * w + (x + 2)]; if (c == empty) { continue; } } // Row 2 if (x - 2 > 0) { c = p[y * w + (x - 2)]; if (c == empty) { continue; } } if (x - 1 > 0) { c = p[y * w + (x - 1)]; if (c == empty) { continue; } } if (x + 1 < w) { c = p[y * w + (x + 1)]; if (c == empty) { continue; } } if (x + 2 < w) { c = p[y * w + (x + 2)]; if (c == empty) { continue; } } // Row 3 if (x - 2 > 0 && y + 1 < h) { c = p[(y + 1) * w + (x - 2)]; if (c == empty) { continue; } } if (x - 1 > 0 && y + 1 < h) { c = p[(y + 1) * w + (x - 1)]; if (c == empty) { continue; } } if (y + 1 < h) { c = p[(y + 1) * w + x]; if (c == empty) { continue; } } if (x + 1 < w && y + 1 < h) { c = p[(y + 1) * w + (x + 1)]; if (c == empty) { continue; } } if (x + 2 < w && y + 1 < h) { c = p[(y + 1) * w + (x + 2)]; if (c == empty) { continue; } } // Row 4 if (x - 2 > 0 && y + 2 < h) { c = p[(y + 2) * w + (x - 2)]; if (c == empty) { continue; } } if (x - 1 > 0 && y + 2 < h) { c = p[(y + 2) * w + (x - 1)]; if (c == empty) { continue; } } if (y + 2 < h) { c = p[(y + 2) * w + x]; if (c == empty) { continue; } } if (x + 1 < w && y + 2 < h) { c = p[(y + 2) * w + (x + 1)]; if (c == empty) { continue; } } if (x + 2 < w && y + 2 < h) { c = p[(y + 2) * w + (x + 2)]; if (c == empty) { continue; } } // If all neighboring pixels are processed // it's clear that the current pixel is not a boundary pixel. rp[i] = cm; } } bmpSrc.UnlockBits(bmData); return bmpSrc; } As I understand it, in order to erode the image (and remove the noise), we need to check each pixel to see if it's surrounding pixels are black, and if so, then it is a border pixel and we need not keep it, which i believe my code does, so it is beyond me why it doesn't work. Any help or pointers would be greatly appreciated Thanks, Chris

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• (Unity)Getting a mirrored mesh from my data structure

  - by Steve

  Here's the background: I'm in the beginning stages of an RTS game in Unity. I have a procedurally generated terrain with a perlin-noise height map, as well as a function to generate a river. The problem is that the graphical creation of the map is taking the data structure of the map and rotating it by 180 degrees. I noticed this problem when i was creating my rivers. I would set the River's height to flat, and noticed that the actual tiles that were flat in the graphical representation were flipped and mirrored. Here's 3 screenshots of the map from different angles: http://imgur.com/a/VLHHq As you can see, if you flipped (graphically) the river by 180 degrees on the z axis, it would fit where the terrain is flattened. I have a suspicion it is being caused by a misunderstanding on my part of how vertices work. Alas, here is a snippet of the code that is used: This code here creates a new array of Tile objects, which hold the information for each tile, including its type, coordinate, height, and it's 4 vertices public DTileMap (int size_x, int size_y) { this.size_x = size_x; this.size_y = size_y; //Initialize Map_Data Array of Tile Objects map_data = new Tile[size_x, size_y]; for (int j = 0; j < size_y; j++) { for (int i = 0; i < size_x; i++) { map_data [i, j] = new Tile (); map_data[i,j].coordinate.x = (int)i; map_data[i,j].coordinate.y = (int)j; map_data[i,j].vertices[0] = new Vector3 (i * GTileMap.TileMap.tileSize, map_data[i,j].Height, -j * GTileMap.TileMap.tileSize); map_data[i,j].vertices[1] = new Vector3 ((i+1) * GTileMap.TileMap.tileSize, map_data[i,j].Height, -(j) * GTileMap.TileMap.tileSize); map_data[i,j].vertices[2] = new Vector3 (i * GTileMap.TileMap.tileSize, map_data[i,j].Height, -(j-1) * GTileMap.TileMap.tileSize); map_data[i,j].vertices[3] = new Vector3 ((i+1) * GTileMap.TileMap.tileSize, map_data[i,j].Height, -(j-1) * GTileMap.TileMap.tileSize); } } This code sets the river tiles to height 0 foreach (Tile t in map_data) { if (t.realType == "Water") { t.vertices[0].y = 0f; t.vertices[1].y = 0f; t.vertices[2].y = 0f; t.vertices[3].y = 0f; } } And below is the code to generate the actual graphics from the data: public void BuildMesh () { DTileMap.DTileMap map = new DTileMap.DTileMap (size_x, size_z); int numTiles = size_x * size_z; int numTris = numTiles * 2; int vsize_x = size_x + 1; int vsize_z = size_z + 1; int numVerts = vsize_x * vsize_z; // Generate the mesh data Vector3[] vertices = new Vector3[ numVerts ]; Vector3[] normals = new Vector3[numVerts]; Vector2[] uv = new Vector2[numVerts]; int[] triangles = new int[ numTris * 3 ]; int x, z; for (z=0; z < vsize_z; z++) { for (x=0; x < vsize_x; x++) { normals [z * vsize_x + x] = Vector3.up; uv [z * vsize_x + x] = new Vector2 ((float)x / size_x, 1f - (float)z / size_z); } } for (z=0; z < vsize_z; z+=1) { for (x=0; x < vsize_x; x+=1) { if (x == vsize_x - 1 && z == vsize_z - 1) { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x - 1, z - 1].vertices [3]; } else if (z == vsize_z - 1) { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x, z - 1].vertices [2]; } else if (x == vsize_x - 1) { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x - 1, z].vertices [1]; } else { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x, z].vertices [0]; vertices [z * vsize_x + x+1] = DTileMap.DTileMap.map_data [x, z].vertices [1]; vertices [(z+1) * vsize_x + x] = DTileMap.DTileMap.map_data [x, z].vertices [2]; vertices [(z+1) * vsize_x + x+1] = DTileMap.DTileMap.map_data [x, z].vertices [3]; } } } } for (z=0; z < size_z; z++) { for (x=0; x < size_x; x++) { int squareIndex = z * size_x + x; int triOffset = squareIndex * 6; triangles [triOffset + 0] = z * vsize_x + x + 0; triangles [triOffset + 2] = z * vsize_x + x + vsize_x + 0; triangles [triOffset + 1] = z * vsize_x + x + vsize_x + 1; triangles [triOffset + 3] = z * vsize_x + x + 0; triangles [triOffset + 5] = z * vsize_x + x + vsize_x + 1; triangles [triOffset + 4] = z * vsize_x + x + 1; } } // Create a new Mesh and populate with the data Mesh mesh = new Mesh (); mesh.vertices = vertices; mesh.triangles = triangles; mesh.normals = normals; mesh.uv = uv; // Assign our mesh to our filter/renderer/collider MeshFilter mesh_filter = GetComponent<MeshFilter> (); MeshCollider mesh_collider = GetComponent<MeshCollider> (); mesh_filter.mesh = mesh; mesh_collider.sharedMesh = mesh; calculateMeshTangents (mesh); BuildTexture (map); } If this looks familiar to you, its because i got most of it from Quill18. I've been slowly adapting it for my uses. And please include any suggestions you have for my code. I'm still in the very early prototyping stage.

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• Getting a mirrored mesh from my data structure

  - by Steve

  Here's the background: I'm in the beginning stages of an RTS game in Unity. I have a procedurally generated terrain with a perlin-noise height map, as well as a function to generate a river. The problem is that the graphical creation of the map is taking the data structure of the map and rotating it by 180 degrees. I noticed this problem when I was creating my rivers. I would set the River's height to flat, and noticed that the actual tiles that were flat in the graphical representation were flipped and mirrored. Here's 3 screenshots of the map from different angles: http://imgur.com/a/VLHHq As you can see, if you flipped (graphically) the river by 180 degrees on the z axis, it would fit where the terrain is flattened. I have a suspicion it is being caused by a misunderstanding on my part of how vertices work. Alas, here is a snippet of the code that is used: This code here creates a new array of Tile objects, which hold the information for each tile, including its type, coordinate, height, and it's 4 vertices public DTileMap (int size_x, int size_y) { this.size_x = size_x; this.size_y = size_y; //Initialize Map_Data Array of Tile Objects map_data = new Tile[size_x, size_y]; for (int j = 0; j < size_y; j++) { for (int i = 0; i < size_x; i++) { map_data [i, j] = new Tile (); map_data[i,j].coordinate.x = (int)i; map_data[i,j].coordinate.y = (int)j; map_data[i,j].vertices[0] = new Vector3 (i * GTileMap.TileMap.tileSize, map_data[i,j].Height, -j * GTileMap.TileMap.tileSize); map_data[i,j].vertices[1] = new Vector3 ((i+1) * GTileMap.TileMap.tileSize, map_data[i,j].Height, -(j) * GTileMap.TileMap.tileSize); map_data[i,j].vertices[2] = new Vector3 (i * GTileMap.TileMap.tileSize, map_data[i,j].Height, -(j-1) * GTileMap.TileMap.tileSize); map_data[i,j].vertices[3] = new Vector3 ((i+1) * GTileMap.TileMap.tileSize, map_data[i,j].Height, -(j-1) * GTileMap.TileMap.tileSize); } } This code sets the river tiles to height 0 foreach (Tile t in map_data) { if (t.realType == "Water") { t.vertices[0].y = 0f; t.vertices[1].y = 0f; t.vertices[2].y = 0f; t.vertices[3].y = 0f; } } And below is the code to generate the actual graphics from the data: public void BuildMesh () { DTileMap.DTileMap map = new DTileMap.DTileMap (size_x, size_z); int numTiles = size_x * size_z; int numTris = numTiles * 2; int vsize_x = size_x + 1; int vsize_z = size_z + 1; int numVerts = vsize_x * vsize_z; // Generate the mesh data Vector3[] vertices = new Vector3[ numVerts ]; Vector3[] normals = new Vector3[numVerts]; Vector2[] uv = new Vector2[numVerts]; int[] triangles = new int[ numTris * 3 ]; int x, z; for (z=0; z < vsize_z; z++) { for (x=0; x < vsize_x; x++) { normals [z * vsize_x + x] = Vector3.up; uv [z * vsize_x + x] = new Vector2 ((float)x / size_x, 1f - (float)z / size_z); } } for (z=0; z < vsize_z; z+=1) { for (x=0; x < vsize_x; x+=1) { if (x == vsize_x - 1 && z == vsize_z - 1) { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x - 1, z - 1].vertices [3]; } else if (z == vsize_z - 1) { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x, z - 1].vertices [2]; } else if (x == vsize_x - 1) { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x - 1, z].vertices [1]; } else { vertices [z * vsize_x + x] = DTileMap.DTileMap.map_data [x, z].vertices [0]; vertices [z * vsize_x + x+1] = DTileMap.DTileMap.map_data [x, z].vertices [1]; vertices [(z+1) * vsize_x + x] = DTileMap.DTileMap.map_data [x, z].vertices [2]; vertices [(z+1) * vsize_x + x+1] = DTileMap.DTileMap.map_data [x, z].vertices [3]; } } } } for (z=0; z < size_z; z++) { for (x=0; x < size_x; x++) { int squareIndex = z * size_x + x; int triOffset = squareIndex * 6; triangles [triOffset + 0] = z * vsize_x + x + 0; triangles [triOffset + 2] = z * vsize_x + x + vsize_x + 0; triangles [triOffset + 1] = z * vsize_x + x + vsize_x + 1; triangles [triOffset + 3] = z * vsize_x + x + 0; triangles [triOffset + 5] = z * vsize_x + x + vsize_x + 1; triangles [triOffset + 4] = z * vsize_x + x + 1; } } // Create a new Mesh and populate with the data Mesh mesh = new Mesh (); mesh.vertices = vertices; mesh.triangles = triangles; mesh.normals = normals; mesh.uv = uv; // Assign our mesh to our filter/renderer/collider MeshFilter mesh_filter = GetComponent<MeshFilter> (); MeshCollider mesh_collider = GetComponent<MeshCollider> (); mesh_filter.mesh = mesh; mesh_collider.sharedMesh = mesh; calculateMeshTangents (mesh); BuildTexture (map); } If this looks familiar to you, its because i got most of it from Quill18. I've been slowly adapting it for my uses. And please include any suggestions you have for my code. I'm still in the very early prototyping stage.

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• How to extract $lastexitcode from c# powershell script execution.

  - by scope-creep

  Hi, I've got a scipt executing in C# using the powershell async execution code on code project here: http://www.codeproject.com/KB/threads/AsyncPowerShell.aspx?display=PrintAll&fid=407636&df=90&mpp=25&noise=3&sort=Position&view=Quick&select=2130851#xx2130851xx I need to return the $lastexitcode and Jean-Paul describes how you can use a custom pshost class to return it. I can't find any method or property in pshost that returns the exit code. This engine I have needs to ensure that script executes correctly. Any help would be appreciated. regards Bob. Its the $lastexitcode and the $? variables I need to bring back. Hi, Finally answered. I found out about the $host variable. It implements a callback into the host, specifically a custom PSHost object, enabling you to return the $lastexitcode. Here is a link to an explanation of $host. http://mshforfun.blogspot.com/2006/08/do-you-know-there-is-host-variable.html It seems to be obscure, badly documented, as usual with powershell docs. Using point 4, calling $host.SetShouldExit(1) returns 1 to the SetShouldExit method of pshost, as described here. http://msdn.microsoft.com/en-us/library/system.management.automation.host.pshost.setshouldexit(VS.85).aspx Its really depends on defining your own exit code defintion. 0 and 1 suffixes I guess. regards Bob.

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• JOGL Double Buffering

  - by Bar

  What is eligible way to implement double buffering in JOGL (Java OpenGL)? I am trying to do that by the following code: ... /** Creating canvas. */ GLCapabilities capabilities = new GLCapabilities(); capabilities.setDoubleBuffered(true); GLCanvas canvas = new GLCanvas(capabilities); ... /** Function display(…), which draws a white Rectangle on a black background. */ public void display(GLAutoDrawable drawable) { drawable.swapBuffers(); gl = drawable.getGL(); gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT); gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); gl.glColor3f(1.0f, 1.0f, 1.0f); gl.glBegin(GL.GL_POLYGON); gl.glVertex2f(-0.5f, -0.5f); gl.glVertex2f(-0.5f, 0.5f); gl.glVertex2f(0.5f, 0.5f); gl.glVertex2f(0.5f, -0.5f); gl.glEnd(); } ... /** Other functions are empty. */ Questions: — When I'm resizing the window, I usually get flickering. As I see it, I have a mistake in my double buffering implementation. — I have doubt, where I must place function swapBuffers — before or after (as many sources says) the drawing? As you noticed, I use function swapBuffers (drawable.swapBuffers()) before drawing a rectangle. Otherwise, I'm getting a noise after resize. So what is an appropriate way to do that? Including or omitting the line capabilities.setDoubleBuffered(true) does not make any effect.

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• Adding & Removing Dynamic Controls in C# WinForms.

  - by gsvirdi

  I have three Tabs in my WinForm; depending on the selected RaioButton in the TabPages[0] I added few dynamic controls on the relevant TabPage. On Button_Click event the controls are added, but the prob is the I'm not able to remove the Dynamically added controls from the other (irrelevant) TabPage. Here's my code: Label label235 = new Label(); TextBox tbMax = new TextBox(); label235.Name = "label235"; tbMax.Name = "txtBoxNoiseMax"; label235.Text = "Noise"; tbMax.ReadOnly = true; label235.ForeColor = System.Drawing.Color.Blue; tbMax.BackColor = System.Drawing.Color.White; label235.Size = new Size(74, 13); tbMax.Size = new Size(85, 20); if (radioButton1.Checked) { label235.Location = new Point(8, 476); tbMax.Location = new Point(138, 473); tabControl.TabPages[1].Controls.Add(label235); tabControl.TabPages[1].Controls.Add(tbMax); tabControl.TabPages[2].Controls.RemoveByKey("label235"); tabControl.TabPages[2].Controls.RemoveByKey("tbMax"); } else { label235.Location = new Point(8, 538); tbMax.Location = new Point(138, 535); tabControl.TabPages[1].Controls.RemoveByKey("label235"); tabControl.TabPages[1].Controls.RemoveByKey("tbMax"); tabControl.TabPages[2].Controls.Add(label235); tabControl.TabPages[2].Controls.Add(tbMax); } Where am I making that mistake?????

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• How to avoid saving a blank model which attributes can be blank

  - by auralbee

  Hello people, I have two models with a HABTM association, let´s say book and author. class Book has_and_belongs_to_many :authors end class Author has_and_belongs_to_many :books end The author has a set of attributes (e.g. first-name,last-name,age) that can all be blank (see validation). validates_length_of :first_name, :maximum => 255, :allow_blank => true, :allow_nil => false In the books_controller, I do the following to append all authors to a book in one step: @book = Book.new(params[:book]) @book.authors.build(params[:book][:authors].values) My question: What would be the easiest way to avoid the saving of authors which fields are all blank to prevent too much "noise" in the database? At the moment, I do the following: validate :must_have_some_data def must_have_some_data empty = true hash = self.attributes hash.delete("created_at") hash.delete("updated_at") hash.each_value do |value| empty = false if value.present? end if (empty) errors.add_to_base("Fields do not contain any data.") end end Maybe there is an more elegant, Rails-like way to do that. Thanks.

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• Should all public methods of an API be documented?

  - by cynicalman

  When writing "library" type classes, is it better practice to always write markup documentation (i.e. javadoc) in java or assume that the code can be "self-documenting"? For example, given the following method stub: /** * Copies all readable bytes from the provided input stream to the provided output * stream. The output stream will be flushed, but neither stream will be closed. * * @param inStream an InputStream from which to read bytes. * @param outStream an OutputStream to which to copy the read bytes. * @throws IOException if there are any errors reading or writing. */ public void copyStream(InputStream inStream, OutputStream outStream) throws IOException { // copy the stream } The javadoc seems to be self-evident, and noise that just needs to be updated if the funcion is changed at all. But the sentence about flushing and not closing the stream could be valuable. So, when writing a library, is it best to: a) always document b) document anything that isn't obvious c) never document (code should speak for itself!) I usually use b), myself (since the code can be self-documenting otherwise)...

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• Finding text orientation in image (angle for rotation)

  - by maximus

  There is an image captured by camera, and I need to find the angle of the text in order to rotate it to make the image better for OCR results. So I know that the fourier transform can be used for that purpose, My question is, does it really gives good results or may be it is better to use something different than that? Can you tell me if there is a good method for this purpose? I am afraid that not every image containing the text will give me a good result after using fourier transform method. Actually, if I make like it is written here: link text (see the part related with an example of text image) calculating the logarithm of the magnitude of the Fourier transform of image with text and then thresholding it, I get that points and I can calculate the line approximately passing through them, and after getting the line calculate the angle, and then make an affine transform, But, what if I do not get a good result every time using this method , and make a false transform? Any ideas please to judge wether the result is correct or not, or may be another method is better? The binary image can contain noise, even if there are not so much of them, the angle found as a result can be not accurate.

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• Figuring out the Nyquist performance limitation of an ADC on an example PIC microcontroller

  - by AKE

  I'm spec-ing the suitability of a dsPIC microcontroller for an analog-to-digital application. This would be preferable to using dedicated A/D chips and a separate dedicated DSP chip. To do that, I've had to run through some computations, pulling the relevant parameters from the datasheets. I'm not sure I've got it right -- would appreciate a check! (EDITED NOTE: The PIC10F220 in the example below was selected ONLY to walk through a simple example to check that I'm interpreting Tacq, Fosc, TAD, and divisor correctly in working through this sort of Nyquist analysis. The actual chips I'm considering for the design are the dsPIC33FJ128MC804 (with 16b A/D) or dsPIC30F3014 (with 12b A/D).) A simple example: PIC10F220 is the simplest possible PIC with an ADC Runs at clock speed of 8MHz. Has an instruction cycle of 0.5us (4 clock steps per instruction) So: Taking Tacq = 6.06 us (acquisition time for ADC, assume chip temp. = 50*C) [datasheet p34] Taking Fosc = 8MHz (? clock speed) Taking divisor = 4 (4 clock steps per CPU instruction) This gives TAD = 0.5us (TAD = 1/(Fosc/divisor) ) Conversion time is 13*TAD [datasheet p31] This gives conversion time 6.5us ADC duration is then 12.56 us [? Tacq + 13*TAD] Assuming at least 2 instructions for load/store: This is another 1 us [0.5 us per instruction] Which would give max sampling rate of 73.7 ksps (1/13.56) Supposing 8 more instructions for real-time processing: This is another 4 us Thus, total ADC/handling time = 17.56us (12.56us + 1us + 4us) So expected upper sampling rate is 56.9 ksps. Nyquist frequency for this sampling rate is therefore 28 kHz. If this is right, it suggests the (theoretical) performance suitability of this chip's A/D is for signals that are bandlimited to 28 kHz. Is this a correct interpretation of the information given in the data sheet in obtaining the Nyquist performance limit? Any opinions on the noise susceptibility of ADCs in PIC / dsPIC chips would be much appreciated! AKE

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• sql server 2005 stored procedure unexpected behaviour

  - by user283405

  i have written a simple stored procedure (run as job) that checks user subscribe keyword alerts. when article posted the stored procedure sends email to those users if the subscribed keyword matched with article title. One section of my stored procedure is: OPEN @getInputBuffer FETCH NEXT FROM @getInputBuffer INTO @String WHILE @@FETCH_STATUS = 0 BEGIN --PRINT @String INSERT INTO #Temp(ArticleID,UserID) SELECT A.ID,@UserID FROM CONTAINSTABLE(Question,(Text),@String) QQ JOIN Article A WITH (NOLOCK) ON A.ID = QQ.[Key] WHERE A.ID > @ArticleID FETCH NEXT FROM @getInputBuffer INTO @String END CLOSE @getInputBuffer DEALLOCATE @getInputBuffer This job run every 5 minute and it checks last 50 articles. It was working fine for last 3 months but a week before it behaved unexpectedly. The problem is that it sends irrelevant results. The @String contains user alert keyword and it matches to the latest articles using Full text search. The normal execution time is 3 minutes but its execution time is 3 days (in problem). Now the current status is its working fine but we are unable to find any reason why it sent irrelevant results. Note: I am already removing noise words from user alert keyword. I am using SQL Server 2005 Enterprise Edition.

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• Is it possible that a single-threaded program is executed simultaneously on more than one CPU core?

  - by Wolfgang Plaschg

  When I run a single-threaded program that i have written on my quad core Intel i can see in the Windows Task Manager that actually all four cores of my CPU are more or less active. One core is more active than the other three, but there is also activity on those. There's no other program (besided the OS kernel of course) running that would be plausible for that activitiy. And when I close my program all activity an all cores drops down to nearly zero. All is left is a little "noise" on the cores, so I'm pretty sure all the visible activity comes directly or indirectly (like invoking system routines) from my program. Is it possible that the OS or the cores themselves try to balance some code or execution on all four cores, even it's not a multithreaded program? Do you have any links that documents this technique? Some infos to the program: It's a console app written in Qt, the Task Manager states that only one thread is running. Maybe Qt uses threads, but I don't use signals or slots, nor any GUI. Link to Task Manager screenshot: http://img97.imageshack.us/img97/6403/taskmanager.png This question is language agnostic and not tied to Qt/C++, i just want to know if Windows or Intel do to balance also single-threaded code on all cores. If they do, how does this technique work? All I can think of is, that kernel routines like reading from disk etc. is scheduled on all cores, but this won't improve performance significantly since the code still has to run synchronous to the kernel api calls. EDIT Do you know any tools to do a better analysis of single and/or multi-threaded programs than the poor Windows Task Manager?

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• Looping HTML5 audio on the iPhone

  - by Peeps

  I'm trying to make a HTML5 webapp that simply plays a sound over and over and over again, on my iPhone. I don't know any Obj-C to do it natively. What I have works fine, but the sound only plays once: <!DOCTYPE html> <html> <head> <title>noisemaker!</title> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <meta name="viewport" content="maximum-scale=1, minimum-scale=1, width=device-width, user-scalable=no" /> <meta name="apple-mobile-web-app-capable" content="yes" /> </head> <body> <audio src="noise.mp3" autoplay controls loop></audio> </body> </html> Is there a way to either bypass the QuickTime audio screen and loop it in the webpage, or get the QuickTime audio screen to loop the sound?

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• Getting nice sound from Java

  - by Peter Lang

  I managed to play midi files using Java, but it produces some distracting noise. I figured out that this is caused by the poor quality soundbank file shipped with Java 6 SDK/JRE. How can I improve that quality? Here is what I have so far: MidiNote example using a Receiver works fine (sounds the same as when playing midi files with other players), so it does not seem to use the Soundbank shipped with Java but the fallback mechanism that uses a hardware MIDI port. Using SimpleMidiPlayer example to play a Midi file works, but the quality is poor. When I delete lib/audio/soundbank.gm, the quality is not bad any more, so the fallback is used again. When I put soundbank-deluxe.gm into the same directory, it is used and produces much better sound. Messing with the clients soundbank file as described in the official Installation Instructions certainly isn't an option, so I tried to put the new soundbank-file into the jar-file and load it: Soundbank soundbank = MidiSystem.getSoundbank( getClass().getResourceAsStream("soundbank-deluxe.gm")); if(synthesizer.isSoundbankSupported(soundbank)) { System.out.println(synthesizer.loadAllInstruments(soundbank)); } This prints true, but the sound remains unchanged. What am I doing wrong loading the soundbank file? Can I force the hardware MIDI port to be used instead of the standard soundbank file?

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• Application lifecycle and onCreate method in the the android sdk

  - by Leif Andersen

  I slapped together a simple test application that has a button, and makes a noise when the user clicks on it. Here are it's method: @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button b = (Button)findViewById(R.id.easy); b.setOnClickListener(this); } public void onClick(View v) { MediaPlayer mp = MediaPlayer.create(this, R.raw.easy); mp.start(); while(true) { if (!mp.isPlaying()) { mp.release(); break; } } } My question is, why is onCreate acting like it's in a while loop? I can click on the button whenever, and it makes the sound. I might think it was just a property of listeners, but the Button object wasn't a member variable. I thought that Android would just go through onCreate onse, and proceed onto the next lifecycle method. Also, I know that my current way of seeing if the sound is playing is crap...I'll get to that later. :) Thank you.

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• Too many false positives when using FxCop.

  - by mark

  Dear ladies and sirs. We are using FxCop and it generates too many false positives to our liking. For instance, if a private method is invoked using reflection, then this method is reported as potentially unused - understandable and we suppress this warning explicitly using the SuppressMessage attribute. However, FxCop reports the same warning for the methods invoked from that method, which we already suppressed warnings about. This is stupid and generates too much noise. There are also false reports on member variables used in these methods. Also, there are problems with generic types (I even saw something about it in MS connect). Anyway, I am wondering if anyone knows whether Microsoft is going to upgrade FxCop, because it seems to be stuck in version 1.36 for a long time. BTW, I we do not use StyleCop, because it is way too picky and we just do not have the time to examine all the zillion messages in order to suppress them all. Besides, the StyleCop report seem to augment, rather than replace FxCop. Maybe anyone can suggest a good alternative to FxCop? We are using VS2008 pro. Thanks.

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• Overload Resolution and Optional Arguments in C# 4

  - by Dale McCoy

  I am working with some code that has seven overloads of a function TraceWrite: void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, string Data = ""); void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, bool LogToFileOnly, string Data = ""); void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, string PieceID, string Data = ""); void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, LogWindowCommandENUM LogWindowCommand, string Data = ""); void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, bool UserMessage, int UserMessagePercent, string Data = ""); void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, string PieceID, LogWindowCommandENUM LogWindowCommand, string Data = ""); void TraceWrite(string Application, LogLevelENUM LogLevel, string Message, LogWindowCommandENUM LogWindowCommand, bool UserMessage, int UserMessagePercent, string Data = ""); (All public static, namespacing noise elided above and throughout.) So, with that background: 1) Elsewhere, I call TraceWrite with four arguments: string, LogLevelENUM, string, bool, and I get the following errors: error CS1502: The best overloaded method match for 'TraceWrite(string, LogLevelENUM, string, string)' has some invalid arguments error CS1503: Argument '4': cannot convert from 'bool' to 'string' Why doesn't this call resolve to the second overload? (TraceWrite(string, LogLevelENUM, string, bool, string = "")) 2) If I were to call TraceWrite with string, LogLevelENUM, string, string, which overload would be called? The first or the third? And why?

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• How to read/write high-resolution (24-bit, 8 channel) .wav files in Java?

  - by dB'

  I'm trying to write a Java application that manipulates high resolution .wav files. I'm having trouble importing the audio data, i.e. converting the .wav file into an array of doubles. When I use a standard approach an exception is thrown. AudioFileFormat as = AudioSystem.getAudioFileFormat(new File("orig.wav")); --> javax.sound.sampled.UnsupportedAudioFileException: file is not a supported file type Here's the file format info according to soxi: dB$ soxi orig.wav soxi WARN wav: wave header missing FmtExt chunk Input File : 'orig.wav' Channels : 8 Sample Rate : 96000 Precision : 24-bit Duration : 00:00:03.16 = 303526 samples ~ 237.13 CDDA sectors File Size : 9.71M Bit Rate : 24.6M Sample Encoding: 32-bit Floating Point PCM Can anyone suggest the simplest method for getting this audio into Java? I've tried using a few techniques. As stated above, I've experimented with the Java AudioSystem (on both Mac and Windows). I've also tried using Andrew Greensted's WavFile class, but this also fails (WavFileException: Compression Code 3 not supported). One workaround is to convert the audio to 16 bits using sox (with the -b 16 flag), but this is suboptimal since it increases the noise floor. Incidentally, I've noticed that the file CAN be read by libsndfile. Is my best bet to write a jni wrapper around libsndfile, or can you suggest something quicker? Note that I don't need to play the audio, I just need to analyze it, manipulate it, and then write it out to a new .wav file. * UPDATE * I solved this problem by modifying Andrew Greensted's WavFile class. His original version only read files encoded as integer values ("format code 1"); my files were encoded as floats ("format code 3"), and that's what was causing the problem. I'll post the modified version of Greensted's code when I get a chance. In the meantime, if anyone wants it, send me a message.

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• Ignore case in Python strings

  - by Paul Oyster

  What is the easiest way to compare strings in Python, ignoring case? Of course one can do (str1.lower() <= str2.lower()), etc., but this created two additional temporary strings (with the obvious alloc/g-c overheads). I guess I'm looking for an equivalent to C's stricmp(). [Some more context requested, so I'll demonstrate with a trivial example:] Suppose you want to sort a looong list of strings. You simply do theList.sort(). This is O(n * log(n)) string comparisons and no memory management (since all strings and list elements are some sort of smart pointers). You are happy. Now, you want to do the same, but ignore the case (let's simplify and say all strings are ascii, so locale issues can be ignored). You can do theList.sort(key=lambda s: s.lower()), but then you cause two new allocations per comparison, plus burden the garbage-collector with the duplicated (lowered) strings. Each such memory-management noise is orders-of-magnitude slower than simple string comparison. Now, with an in-place stricmp()-like function, you do: theList.sort(cmp=stricmp) and it is as fast and as memory-friendly as theList.sort(). You are happy again. The problem is any Python-based case-insensitive comparison involves implicit string duplications, so I was expecting to find a C-based comparisons (maybe in module string). Could not find anything like that, hence the question here. (Hope this clarifies the question).

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• Database for Python Twisted

  - by Will

  There's an API for Twisted apps to talk to a database in a scalable way: twisted.enterprise.dbapi The confusing thing is, which database to pick? The database will have a Twisted app that is mostly making inserts and updates and relatively few selects, and then other strictly-read-only clients that are accessing the database directly making selects. (The read-only users are not necessarily selecting the data that the Twisted app is inserting; its not as though the database is being used as a message-queue) My understanding - which I'd like corrected/adviced - is that: Postgres is a great DB, but all the Python bindings - and there is a confusing maze of them - are abandonware There is psycopg2, but that makes a lot of noise about doing its own connection-pooling and things; does this co-exist gracefully/usefully/transparently with the Twisted async database connection pooling and such? SQLLite is a great database for little things but if used in a multi-user way it does whole-database locking, so performance would suck in the usage pattern I envisage MySQL - after the Oracle takeover, who'd want to adopt it now or adopt a fork? Is there anything else out there?

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• how would you like computer science classes to be taught?

  - by aaa

  hello I am a graduate student now, and hopefully someday I will teach. my interests are C++, Python, embedded languages, and scientific computing. Meanwhile I daydream about how I would teach. I was not quite happy with my undergraduate university as I found many computer science classes lacking. so I would like to ask you, if you were a student, how would you like your computer science classes to be taught? I understand it is a very subjective question, but nevertheless I think it's important to know what people want. Some specific points I am interested in: should computer languages be taught explicitly, or should students be required to pick up language on their own? what is better for learning, tests, projects, some sort of take-home exam? how do you think classtime should be used? theory, introduction, explanations, etc.? do you think the group projects are important? how much about computer architecture do you want to learn in computer science class, not necessarily assembler class. should particular operating system/editor be mandated or encouraged? Thanks thank you for your comments. Question has been closed because it is a discussion question rather than Q&A. If you know appropriate website for discussions of such sort with low noise ratio, please let me know.

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• Help me choose a web development framework/platform that will make me learn something

  - by Sergio Tapia

  I'm having a bit of an overload of information these past two days. I'm planning to start my own website that will allow local businesses to list their items on sale, and then users can come in and search for "Abercrombie t-shirt" and the stores that sell them will be listed. It's a neat little project I'm really excited for and I'm sure it'll take off, but I'm having problems from the get go. Sure I could use ASP.Net for it, I'm a bit familiar with it and the IDE for ASP.Net pages is bar-none, but I feel this is a great chance for me to learn something new to branch out a bit and not regurgitate .NET like a robot. I've been looking and asking around but it's all just noise and I can't make an educated decision. Can you help me choose a framework/platform that will make me learn something that's a nice thing to know in the job market, but also nice for me to grow as a professional? So far I've looked at: Ruby on Rails Kohana CakePHP CodeIgniter Symfony But they are all very esoteric to me, and I have trouble even finding out which IDE to use to that will let me use auto-complete for the proprietary keywords/methods. Thank you for your time.

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• Who likes #regions in Visual Studio?

  - by Nicholas

  Personally I can't stand region tags, but clearly they have wide spread appeal for organizing code, so I want to test the temperature of the water for other MS developer's take on this idea. My personal feeling is that any sort of silly trick to simplify code only acts to encourage terrible coding behavior, like lack of cohesion, unclear intention and poor or incomplete coding standards. One programmer told me that code regions helped encourage coding standards by making it clear where another programmer should put his or her contributions. But, to be blunt, this sounds like a load of horse manure to me. If you have a standard, it is the programmer's job to understand what that standard is... you should't need to define it in every single class file. And, nothing is more annoying than having all of your code collapsed when you open a file. I know that cntrl + M, L will open everything up, but then you have the hideous "hash region definition" open and closing lines to read. They're just irritating. My most stead fast coding philosophy is that all programmer should strive to create clear, concise and cohesive code. Region tags just serve to create noise and redundant intentions. Region tags would be moot in a well thought out and intentioned class. The only place they seem to make sense to me, is in automatically generated code, because you should never have to read that outside of personal curiosity.

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• Truly declarative language?

  - by gjvdkamp

  Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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