I have an array of audio data, which is a lot of Int32 numbers represented by array of bytes (each 4 byte element represents an Int32) and i want to do some manipulation on the data (for example, add 10 to each Int32).
I converted the bytes to Int32, do the manipulation and convert it back to bytes as in this example:
//byte[] buffer;
for (int i=0; i<buffer.Length; i+=4)
{
Int32 temp0 = BitConverter.ToInt32(buffer, i);
temp0 += 10;
byte[] temp1 = BitConverter.GetBytes(temp0);
for (int j=0;j<4;j++)
{
buffer[i + j] = temp1[j];
}
}
But I would like to know if there is a better way to do such manipulation.
You can check the .NET Reference Source for pointers (grin) on how to convert from/to big endian.
class intFromBigEndianByteArray {
public byte[] b;
public int this[int i] {
get {
i <<= 2; // i *= 4; // optional
return (int)b[i] << 24 | (int)b[i + 1] << 16 | (int)b[i + 2] << 8 | b[i + 3];
}
set {
i <<= 2; // i *= 4; // optional
b[i ] = (byte)(value >> 24);
b[i + 1] = (byte)(value >> 16);
b[i + 2] = (byte)(value >> 8);
b[i + 3] = (byte)value;
}
}
}
and sample use:
byte[] buffer = { 127, 255, 255, 255, 255, 255, 255, 255 };//big endian { int.MaxValue, -1 }
//bool check = BitConverter.IsLittleEndian; // true
//int test = BitConverter.ToInt32(buffer, 0); // -129 (incorrect because little endian)
var fakeIntBuffer = new intFromBigEndianByteArray() { b = buffer };
fakeIntBuffer[0] += 2; // { 128, 0, 0, 1 } = big endian int.MinValue - 1
fakeIntBuffer[1] += 2; // { 0, 0, 0, 1 } = big endian 1
Debug.Print(string.Join(", ", buffer)); // "128, 0, 0, 0, 1, 0, 0, 1"
For better performance you can look into parallel processing and SIMD instructions - Using SSE in C#
For even better performance, you can look into Utilizing the GPU with c#
How about the following approach:
struct My
{
public int Int;
}
var bytes = Enumerable.Range(0, 20).Select(n => (byte)(n + 240)).ToArray();
foreach (var b in bytes) Console.Write("{0,-4}", b);
// Pin the managed memory
GCHandle handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
for (int i = 0; i < bytes.Length; i += 4)
{
// Copy the data
My my = (My)Marshal.PtrToStructure<My>(handle.AddrOfPinnedObject() + i);
my.Int += 10;
// Copy back
Marshal.StructureToPtr(my, handle.AddrOfPinnedObject() + i, true);
}
// Unpin
handle.Free();
foreach (var b in bytes) Console.Write("{0,-4}", b);
I made it just for fun.
Not sure that's less ugly.
I don't know, will it be faster? Test it.
I'm trying to optimize my screen sharing app. I've already used a few ways to make it faster and stable, such as only sending the deltas between two frames, and using Gzip to compress the data.
This is my client code:
private void Form1_Load(object sender, EventArgs e)
{
Thread th = new Thread(startSend);
th.Start();
}
private void startSend()
{
Bitmap curr;
Bitmap diff;
encoderParams.Param[0] = qualityParam;
Bitmap pre = screenshot();
bmpBytes = imageToByteArray(pre);
SendVarData(handler, bmpBytes);
while (true)
{
curr= screenshot();
diff= Difference(pre, curr);
bmpBytes = imageToByteArray(diff);
SendVarData(handler, bmpBytes);
pre = curr;
}
}
Screenshot:
public Bitmap screenshot()
{
Bitmap screenshot = new Bitmap(SystemInformation.VirtualScreen.Width,
SystemInformation.VirtualScreen.Height,
PixelFormat.Format24bppRgb);
Graphics screenGraph = Graphics.FromImage(screenshot);
screenGraph.CopyFromScreen(0,
0,
0,
0,
SystemInformation.VirtualScreen.Size,
CopyPixelOperation.SourceCopy);
return screenshot;
}
The Difference method:
public Bitmap Difference(Bitmap bmp0, Bitmap bmp1)
{
Bitmap bmp2;
int Bpp = 3;
bmp2 = new Bitmap(bmp0.Width, bmp0.Height, bmp0.PixelFormat);
var bmpData0 = bmp0.LockBits(
new Rectangle(0, 0, bmp0.Width, bmp0.Height),
ImageLockMode.ReadOnly, bmp0.PixelFormat);
var bmpData1 = bmp1.LockBits(
new Rectangle(0, 0, bmp1.Width, bmp1.Height),
ImageLockMode.ReadOnly, bmp1.PixelFormat);
var bmpData2 = bmp2.LockBits(
new Rectangle(0, 0, bmp2.Width, bmp2.Height),
ImageLockMode.ReadWrite, bmp2.PixelFormat);
bmp0.UnlockBits(bmpData0);
bmp1.UnlockBits(bmpData1);
bmp2.UnlockBits(bmpData2);
int len = bmpData0.Height * bmpData0.Stride;
// MessageBox.Show(bmpData0.Stride.ToString());
bool changed=false;
byte[] data0 = new byte[len];
byte[] data1 = new byte[len];
byte[] data2 = new byte[len];
Marshal.Copy(bmpData0.Scan0, data0, 0, len);
Marshal.Copy(bmpData1.Scan0, data1, 0, len);
Marshal.Copy(bmpData2.Scan0, data2, 0, len);
for (int i = 0; i < len; i += Bpp)
{
changed = ((data0[i] != data1[i])
|| (data0[i + 1] != data1[i + 1])
|| (data0[i + 2] != data1[i + 2]));
// this.Invoke(new Action(() => this.Text = changed.ToString()));
data2[i] = changed ? data1[i] : (byte)2; // special markers
data2[i + 1] = changed ? data1[i + 1] : (byte)3; // special markers
data2[i + 2] = changed ? data1[i + 2] : (byte)7; // special markers
if (Bpp == 4) data2[i + 3] =
changed ? (byte)255 : (byte)42; // special markers
}
// this.Invoke(new Action(() => this.Text = changed.ToString()));
Marshal.Copy(data2, 0, bmpData2.Scan0, len);
return bmp2;
}
and the SendVarData function:
int total = 0;
byte[] datasize;
private int SendVarData(Socket s, byte[] data)
{
total = 0;
int size = data.Length;
int dataleft = size;
int sent;
datasize = BitConverter.GetBytes(size);
sent = s.Send(datasize);
sent = s.Send(data, total, dataleft, SocketFlags.None);
total += sent;
dataleft -= sent;
// MessageBox.Show("D");
return total;
}
This is the server - I'm just receiving a full image in the beginning, and then just deltas:
public void startListening()
{
prev = byteArrayToImage(ReceiveVarData(client.Client));
theImage.Image = prev;
while (true)
{
data = ReceiveVarData(client.Client);
curr = byteArrayToImage(data) ;
merge = Merge(prev, curr);
theImage.Image = merge;
count++;
prev = merge;
}
}
public static Bitmap Merge(Bitmap bmp0, Bitmap bmp1)
{
int Bpp = 3;
Bitmap bmp2 = new Bitmap(bmp0.Width, bmp0.Height, bmp0.PixelFormat);
var bmpData0 = bmp0.LockBits(
new System.Drawing.Rectangle(0, 0, bmp0.Width, bmp0.Height),
ImageLockMode.ReadOnly, bmp0.PixelFormat);
var bmpData1 = bmp1.LockBits(
new System.Drawing.Rectangle(0, 0, bmp1.Width, bmp1.Height),
ImageLockMode.ReadOnly, bmp1.PixelFormat);
var bmpData2 = bmp2.LockBits(
new System.Drawing.Rectangle(0, 0, bmp2.Width, bmp2.Height),
ImageLockMode.ReadWrite, bmp2.PixelFormat);
bmp0.UnlockBits(bmpData0);
bmp1.UnlockBits(bmpData1);
bmp2.UnlockBits(bmpData2);
int len = bmpData0.Height * bmpData0.Stride;
byte[] data0 = new byte[len];
byte[] data1 = new byte[len];
byte[] data2 = new byte[len];
Marshal.Copy(bmpData0.Scan0, data0, 0, len);
Marshal.Copy(bmpData1.Scan0, data1, 0, len);
Marshal.Copy(bmpData2.Scan0, data2, 0, len);
for (int i = 0; i < len; i += Bpp)
{
bool toberestored = (data1[i] != 2 && data1[i + 1] != 3 &&
data1[i + 2] != 7 && data1[i + 2] != 42);
if (toberestored)
{
data2[i] = data1[i];
data2[i + 1] = data1[i + 1];
data2[i + 2] = data1[i + 2];
if (Bpp == 4) data2[i + 3] = data1[i + 3];
}
else
{
data2[i] = data0[i];
data2[i + 1] = data0[i + 1];
data2[i + 2] = data0[i + 2];
if (Bpp == 4) data2[i + 3] = data0[i + 3];
}
}
Marshal.Copy(data2, 0, bmpData2.Scan0, len);
return bmp2;
}
I think it's coded fine, but I'm still unable to get more than 6~7fps (of 8kb-100kb) when running on 2 different computers with a fast and stable internet connection, and a maximum of 11fps when running both client and server on the same computer. I think it's because of the complexity of the delta and merging algorithms, but i dont know.
I would very appreciate if anyone could suggest how could optimize it further.
You may organize data2 in a different manner to send less data.
The below "compression" algorithm is very basic but will provide an improved compression compared to your implelmentation.
Search for differences, by identifying start and end of consecutive differences. When you find an interval where all pixels are different, store the length of identical data before that interval using 2 bytes, then store the number of consecutive differences, finally write 3 RGB bytes for each different pixel.
In case of 65535 different pixels, block the max interval length to 65535 and after storing the interval values. The next difference interval starting just after the stored interval, the identical count for next interval will be 0.
In case of 65535 identical pixels, just write $FFFF followed by $0000 indicating an empty sequence of different pixels.
Clarification: What I mean by "identifying start and end of consecutive differences" ?
In the above example, letters identify colors, i.e W(white), P(Pink), O(Orange):
The word "identical" refers to a comparison between data 0 and data1 (not comparing data1[i] with data1[i-1]).
Data0 = WWPWWOWOOOWWOOOPP
Data1 = WWPWPWP OOOWWPP OPP
You have 4 identical pixels (WWPW) followed by an interval (length 3) starting on the 4th character and ending on the 6th where all pixels are different. Then five identical pixels, followed by a new interval with 2 differences. At the end, a few common pixels.
The output for data2 will be (the text in parenthesis are not part of the buffer and explains the previous buffer values :
04 00 (4 identical pixels) 03 00 (3 different pixels coded in next 9 bytes)
Pr Pg Pb (3 bytes RGB code for P) Wr Wg Wb (RGB code for W) Pr Pg Pb (RGB code for P)
05 00 (5 identical pixels) 03 00 (2 different pixels coded in next 6 bytes)
Pr Pg Pb (RGB code for P) ...
The code to write differences would look like to the following.
I let you build the code adressing the opposite action, i.e. reading differences to update the previous image.
Data2Index = 0 ; // next index for additions in data2 ;
int idcount = 0 ;
int diffstart = -1 ;
int diffstart = -1 ;
for (int i = 0; i < len; i += Bpp)
{
changed = ((data0[i] != data1[i])
|| (data0[i + 1] != data1[i + 1])
|| (data0[i + 2] != data1[i + 2]));
if (!changed)
{
if (idcount==ushort.MaxValue)
{ // still identical, but there is a limitation on count
// write to data2 the identical count + differencecount equals to 0
AddIdCountDiffCountAndDifferences(idcount,0,0) ;
idcount = 0 ;
}
if (diffstart>0)
{ // after 0 or more identical values, a change was found
// write to data2 the identical count + difference count + different pixels
AddIdCountDiffCountAndDifferences(idcount,diffcount,diffstart) ;
idcount = 0 ;
diffcount= 0 ;
diffstart=-1 ;
}
else identicalcount++ ; // still identical, continue until difference found
}
else if (diffstart<0)
{ // a difference is found after a sequence of identical pixels, store the index of first difference
diffstart=i ; diffcount=1 ;
}
else
{ // different pixel follows another difference (and limitation not reached)
if (diffcount<ushort.MaxVakue) diffcount++ ;
}
else
{ // limitation reached, i.e. diffcount equals 65535
AddIdCountDiffCountAndDifferences(0,diffcount,diffstart) ;
diffstart+=diffcount ;
diffcount=0 ;
}
The procedure used to fill data2 here:
private int Data2Index = 0 ; // to be reset before
private void AddIdCountDiffCountAndDifferences(int idcount,int diffcount,int diffstart)
{
data2[Data2Index++]=(byte)(idcount && 0xFF) ; // low byte of the int
data2[Data2Index++]=(byte)(idcount >> 8 && 0xFF) ; // second byte of the int
data2[Data2Index++]=(byte)(diffcount && 0xFF) ; // low byte of the int
data2[Data2Index++]=(byte)(diffcount >> 8 && 0xFF) ; // second byte of the int
for (int i=0;i<diffcount;i++)
{
data2[Data2Index++]=data1[diffstart+Bpp*i ] ;
data2[Data2Index++]=data1[diffstart+Bpp*i+1] ;
data2[Data2Index++]=data1[diffstart+Bpp*i+2] ;
}
}
I copied some code somewhere in this forum that represents a wav file and wrote it into a MemoryStream. I try to play it when clicking on a button with some variables passed in: PlayBeep(8000,500,16383);
But the emulator crashes and says:
An exception of type 'System.InvalidOperationException' occurred in
Microsoft.Xna.Framework.ni.dll but was not handled in user code
Additional information: FrameworkDispatcher.Update has not been called
Here is the code:
public static void PlayBeep(UInt16 frequency, int msDuration, UInt16 volume = 16383)
{
var mStrm = new MemoryStream();
BinaryWriter writer = new BinaryWriter(mStrm);
const double TAU = 2 * Math.PI;
int formatChunkSize = 16;
int headerSize = 8;
short formatType = 1;
short tracks = 1;
int samplesPerSecond = 44100;
short bitsPerSample = 16;
short frameSize = (short)(tracks * ((bitsPerSample + 7) / 8));
int bytesPerSecond = samplesPerSecond * frameSize;
int waveSize = 4;
int samples = (int)((decimal)samplesPerSecond * msDuration / 1000);
int dataChunkSize = samples * frameSize;
int fileSize = waveSize + headerSize + formatChunkSize + headerSize + dataChunkSize;
// var encoding = new System.Text.UTF8Encoding();
writer.Write(0x46464952); // = encoding.GetBytes("RIFF")
writer.Write(fileSize);
writer.Write(0x45564157); // = encoding.GetBytes("WAVE")
writer.Write(0x20746D66); // = encoding.GetBytes("fmt ")
writer.Write(formatChunkSize);
writer.Write(formatType);
writer.Write(tracks);
writer.Write(samplesPerSecond);
writer.Write(bytesPerSecond);
writer.Write(frameSize);
writer.Write(bitsPerSample);
writer.Write(0x61746164); // = encoding.GetBytes("data")
writer.Write(dataChunkSize);
{
double theta = frequency * TAU / (double)samplesPerSecond;
// 'volume' is UInt16 with range 0 thru Uint16.MaxValue ( = 65 535)
// we need 'amp' to have the range of 0 thru Int16.MaxValue ( = 32 767)
double amp = volume >> 2; // so we simply set amp = volume / 2
for (int step = 0; step < samples; step++)
{
short s = (short)(amp * Math.Sin(theta * (double)step));
writer.Write(s);
}
}
mStrm.Seek(0, SeekOrigin.Begin);
SoundEffect mySoundEffect = SoundEffect.FromStream(mStrm);
//mySoundEffect.Play(); //Crashing here
writer.Close();
mStrm.Close();
}
I am trying to implement a function which takes an wav file, runs a 100th of a second worth of audio through the FFT by AForge. When I change the offset to alter where in the audio I am computing through the FFT, sometimes I will get results in which I can show in my graph but most of the time I get a complex array of NaN's. Why could this be?
Here is my code.
public double[] test()
{
OpenFileDialog file = new OpenFileDialog();
file.ShowDialog();
WaveFileReader reader = new WaveFileReader(file.FileName);
byte[] data = new byte[reader.Length];
reader.Read(data, 0, data.Length);
samepleRate = reader.WaveFormat.SampleRate;
bitDepth = reader.WaveFormat.BitsPerSample;
channels = reader.WaveFormat.Channels;
Console.WriteLine("audio has " + channels + " channels, a sample rate of " + samepleRate + " and bitdepth of " + bitDepth + ".");
float[] floats = new float[data.Length / sizeof(float)];
Buffer.BlockCopy(data, 0, floats, 0, data.Length);
size = 2048;
int inputSamples = samepleRate / 100;
int offset = samepleRate * 15 * channels;
int y = 0;
Complex[] complexData = new Complex[size];
float[] window = CalcWindowFunction(inputSamples);
for (int i = 0; i < inputSamples; i++)
{
complexData[y] = new Complex(floats[i * channels + offset] * window[i], 0);
y++;
}
while (y < size)
{
complexData[y] = new Complex(0, 0);
y++;
}
FourierTransform.FFT(complexData, FourierTransform.Direction.Forward);
double[] arr = new double[complexData.Length];
for (int i = 0; i < complexData.Length; i++)
{
arr[i] = complexData[i].Magnitude;
}
Console.Write("complete, ");
return arr;
}
private float[] CalcWindowFunction(int inputSamples)
{
float[] arr = new float[size];
for(int i =0; i<size;i++){
arr[i] = 1;
}
return arr;
}
A complex array of NaNs is usually the result of one of the inputs to the FFT being a NaN. To debug, you might check all the values in the input array before the FFT to make sure they are within some valid range, given the audio input scaling.
Question of the title.Recently using GDAL reading Terrasar—X data and dividing imaginary and real parts Like software NEST confuses me a lot.Any help and suggestion will be highly appreciated.Below is my implementation method:
string dataPath = #"E:\SARDATA\SampleData\TerraSar-X\SO_000009564_0002_1\SO_000009564_0002_1\TSX1_SAR__SSC______HS_S_SRA_20090223T204240_20090223T204241\TSX1_SAR__SSC______HS_S_SRA_20090223T204240_20090223T204241.xml";
Gdal.AllRegister();
Dataset dataset = Gdal.OpenShared(dataPath, Access.GA_ReadOnly);
Band band = dataset.GetRasterBand(1);
int xSize = band.XSize;
int ySize = band.YSize;
short[] realArray = new short[xSize * ySize];
short[] imgArray = new short[xSize * ySize];
if (band.DataType == DataType.GDT_CInt16)
{
short[] tmpArray = new short[2 * xSize * ySize];
band.ReadRaster(0, 0, xSize, ySize, tmpArray, xSize, ySize, 0, 0);
for (int i = 0; i < tmpArray.Length;i++ )
{
realArray[i] = tmpArray[i / 2];
imgArray[i] = tmpArray[i / 2 + 1];
}
tmpArray = null;
}
I think I have a solution to your problem. I also tried to read a complex TerraSAR-X and I encountered your answer.
The complex file format merges two Int16 for CInt16 and two Int32 for CInt32.
To read correctly the complex data you should split an Integer into two shorts. The correct reading should look like this:
string dataPath = #"E:\SARDATA\SampleData\TerraSar-X\SO_000009564_0002_1\SO_000009564_0002_1\TSX1_SAR__SSC______HS_S_SRA_20090223T204240_20090223T204241\TSX1_SAR__SSC______HS_S_SRA_20090223T204240_20090223T204241.xml";
Gdal.AllRegister();
Dataset dataset = Gdal.OpenShared(dataPath, Access.GA_ReadOnly);
Band band = dataset.GetRasterBand(1);
int xSize = band.XSize;
int ySize = band.YSize;
short[] realArray = new short[xSize * ySize];
short[] imgArray = new short[xSize * ySize];
if (band.DataType == DataType.GDT_CInt16)
{
short[] tmpArray = new short[xSize * ySize];
band.ReadRaster(0, 0, xSize, ySize, tmpArray, xSize, ySize, 0, 0);
for (int i = 0; i < tmpArray.Length;i++ )
{
int value = tmpArray[i];
realArray[i] = (short)(value>>16);
imgArray[i] = (short)(value & 0xffff);
}
tmpArray = null;
}