This program with full C# source code allows you to dump the calls
captured in Tethereal, Ethereal, or
Wireshark. You will have the sound files to
play Incoming, Outgoing, and Combined audio. The program demonstrates
the use of ULAW to Signed Linear
functions and Signed Linear to
ULAW.
tshark -w myoutput.pcap
pcaptosip_rtp myoutput.pcap
We use this to debug some of our Phone Notify
service calls. We can call into a VOIP system and check how notify
performs with answering machines and more.
private static byte linear2ulaw(short pcm_val) /*2's complement(16-bit range)*/
{
short mask;
short seg;
byte uval;
/* Get the sign and the magnitude of the value. */
pcm_val = (short)((int)pcm_val >> 2);
if (pcm_val < 0)
{
pcm_val = (short)-pcm_val;
mask = 0x7F;
}
else
{
mask = 0xFF;
}
if (pcm_val > 8159) pcm_val = 8159; /* clip the magnitude */
pcm_val += 0x84 >> 2;
/* Convert the scaled magnitude to segment number. */
seg = search(pcm_val, seg_end, 8);
/*
* Combine the sign, segment, quantization bits;
* and complement the code word.
*/
if (seg >= 8) /* out of range, return maximum value. */
return (byte)(0x7F ^ mask);
else
{
uval = (byte)((seg << 4) | ((pcm_val >> (seg + 1)) & 0xF));
return ((byte)(uval ^ mask));
}
}
static short search(
short val,
short[] table,
short size)
{
short i;
for (i = 0; i < size; i++)
{
if (val <= table[i])
return (i);
}
return (size);
}
static short[] seg_end = { 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF };
private static Int16[] ULAW_TO_LINEAR_16_BIT = new Int16[]{
-32124, -31100, -30076, -29052, -28028, -27004, -25980, -24956, -23932, -22908, -21884, -20860, -19836, -18812,
-17788, -16764, -15996, -15484, -14972, -14460, -13948, -13436, -12924, -12412, -11900, -11388, -10876, -10364,
-9852, -9340, -8828, -8316, -7932, -7676, -7420, -7164, -6908, -6652, -6396, -6140, -5884, -5628, -5372, -5116,
-4860, -4604, -4348, -4092, -3900, -3772, -3644, -3516, -3388, -3260, -3132, -3004, -2876, -2748, -2620, -2492,
-2364, -2236, -2108, -1980, -1884, -1820, -1756, -1692, -1628, -1564, -1500, -1436, -1372, -1308, -1244, -1180,
-1116, -1052, -988, -924, -876, -844, -812, -780, -748, -716, -684, -652, -620, -588, -556, -524, -492, -460,
-428, -396, -372, -356, -340, -324, -308, -292, -276, -260, -244, -228, -212, -196, -180, -164, -148, -132, -120,
-112, -104, -96, -88, -80, -72, -64, -56, -48, -40, -32, -24, -16, -8, 0, 32124, 31100, 30076, 29052, 28028,
27004, 25980, 24956, 23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764, 15996, 15484, 14972, 14460, 13948,
13436, 12924, 12412, 11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316, 7932, 7676, 7420, 7164, 6908, 6652, 6396,
6140, 5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092, 3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004, 2876, 2748,
2620, 2492, 2364, 2236, 2108, 1980, 1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436, 1372, 1308, 1244, 1180, 1116,
1052, 988, 924, 876, 844, 812, 780, 748, 716, 684, 652, 620, 588, 556, 524, 492, 460, 428, 396, 372, 356, 340,
324, 308, 292, 276, 260, 244, 228, 212, 196, 180, 164, 148, 132, 120, 112, 104, 96, 88, 80, 72, 64, 56, 48, 40,
32, 24, 16, 8, 0};
}
static void ByteArrayToStructure(byte[] bytearray, ref object obj)
{
int len = Marshal.SizeOf(obj);
IntPtr i = Marshal.AllocHGlobal(len);
Marshal.Copy(bytearray, 0, i, len);
obj = Marshal.PtrToStructure(i, obj.GetType());
Marshal.FreeHGlobal(i);
}
static byte[] StructureToByteArray(object obj)
{
int len = Marshal.SizeOf(obj);
byte[] arr = new byte[len];
IntPtr ptr = Marshal.AllocHGlobal(len);
Marshal.StructureToPtr(obj, ptr, true);
Marshal.Copy(ptr, arr, 0, len);
Marshal.FreeHGlobal(ptr);
return arr;
}