英文原文地址：https://www.codeproject.com/Articles/85763/C-NET-RTP-MJPEG-Player
通过RTP实现RTP和MJPEG，支持大型帧和组播。
介绍
这是C＃中RTP / MJPEG协议的实现。 我在2005年写了这个代码。
背景
这个代码被用于Elphel网络摄像机，组播RTP / MJPEG，但它应该几乎兼容所有的RTP / MJPEG技术。 此代码是通过阅读相关的RFC编写的。
使用代码
RtpPacket.cs
using System;
using System.Collections.Generic;
using System.Text;
namespace RTPLib
{
public class RtpPacket
{
public static readonly int rtp_version = 2; /* the version of RTP supported */
public static readonly int rtp_length = 12; /* fixed RTP packet header size */
public int version; /* the version of RTP should be 2 */
public byte padding; /* the padding flag **/
public byte extension; /* the extension flag - if any extra headers
for higher protocol */
public int csrc_count; /* the source count */
public bool marker; /* the marker status */
public int payload_type; /* the type of payload */
public ushort sequence_no; /* the sequence number of the RTP packet */
public uint timestamp; /* the timestamp of the RTP packet */
public uint source_id; /* the source id of the RTP packet */
public RtpPacket(byte[] _data)
{
decode(_data);
}
public void decode(byte[] data)
{
/*byte[] data = new byte[12];
Array.Copy(_data, data, 12);*/ /* there should be no need
to copy the header */
version = data[0] >> 6;
padding = (byte)(0x1 & (data[0] >> 5));
extension = (byte)(0x1 & (data[0] >> 4));
csrc_count = 0x1F & (data[0]);
marker = ((data[1] >> 7) == 1);
payload_type = data[1] & 0x7f; /* we will assume it's 26 -> RTP/MJPEG */
sequence_no = Utils.HostToNetworkOrderShort
(System.BitConverter.ToUInt16(data, 2));
timestamp = Utils.SwapUnsignedInt(System.BitConverter.ToUInt32(data, 4));
source_id = Utils.SwapUnsignedInt(System.BitConverter.ToUInt32(data, 8));
}
}
}JPEGFrame.cs
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Drawing;
using System.Runtime.InteropServices;
using System.ComponentModel;
namespace RTPLib
{
public unsafe class JPEGFrame : IDisposable
{
private byte[] _buffer;
private int _offset;
private MemoryStream _stream_buffer;
private bool _alreadyDisposed;
private Image _frame_img;
private bool _initialized;
public int type_specific; /** 8 bits **/
public int fragment_offset; /** 24 bits **/
public int next_fragment_offset;
/** 0-63 fixed q no restart markers **/
public int jpeg_type; /** 8 bits **/
/** 64-127 Restart Marker header appears immediately
following the main JPEG header **/
public int q; /** 8 bits **/ /** multiply by 8 **/
/** 128-255 qtable is present and right after the
restart marker header if present **/
/** 128 to 254 q is static to be read only once**/
public int width; /** 8 bits **/ /** multiply by 8 **/
public int height; /** 8 bits **/ /** multiply by 8 **/
/** Restart Marker header **/
public ushort restart_interval; /** 16 bits **/
public ushort f; /** 1 bit **/
public ushort l; /** 1 bit **/
public ushort restart_count; /** 14 bits **/ /** f and l must be set to 1
and 0x3FFF if set reassemble the frame before decoding **/
/** Quantization Table header **/
/** must be present after the restart marker header if it is present**/
public ushort mbz; /** 8 bits **/
public ushort precision; /** 8 bits **/
public ushort qlength; /** 16 bits **/
public byte[] qtable; /** qtables **/
public static int max_size = 8192 * 250;
private byte[] _frag; /** hold the fragment offset number for conversion **/
private ImageProcessing imgProceesor;
private unsafe byte* buffer_ptr;
public JPEGFrame()
{
//qtable = new byte[1024];
//imgProceesor = new ImageProcessing();
_buffer = new byte[max_size];
unsafe
{
fixed (byte* buf_ptr = _buffer)
buffer_ptr = buf_ptr;
}
_frag = new byte[4];
_initialized = false;
_offset = 0;
}
public bool Decode(byte * data, int offset) //Decode(ref byte[] data, int offset)
{
if (_initialized == false)
{
type_specific = data[offset + 0];
_frag[0] = data[offset + 3];
_frag[1] = data[offset + 2];
_frag[2] = data[offset + 1];
_frag[3] = 0x0;
fragment_offset = System.BitConverter.ToInt32(_frag, 0);
jpeg_type = data[offset + 4];
q = data[offset + 5];
width = data[offset + 6];
height = data[offset + 7];
_frag[0] = data[offset + 8];
_frag[1] = data[offset + 9];
restart_interval = (ushort)(System.BitConverter.ToUInt16
(_frag, 0) & 0x3FF);
//restart_interval = (ushort)(System.BitConverter.ToUInt16
(data, offset + 8) & 0x3FF);
if (width == 0) /** elphel 333 full image size more than
just one byte less that < 256 **/
width = 256;
byte[] tmp = new byte[1024];
_offset = Utils.MakeTables(q, jpeg_type, height, width, tmp);
qtable = new byte[_offset];
Array.Copy(tmp, 0, _buffer, 0, _offset);
Array.Copy(tmp, 0, qtable, 0, _offset); //not needed but
_initialized = true;
tmp = null;
/*Utils.StaticDispose();
Utils.Dispose();*/
GC.Collect();
}
else
{
_frag[0] = data[15]; //12 + 3
_frag[1] = data[14]; //12 + 2
_frag[2] = data[13]; //12 + 1]
_frag[3] = 0x0;
fragment_offset = System.BitConverter.ToInt32(_frag, 0);
_frag[0] = data[offset + 8];
_frag[1] = data[offset + 9];
restart_interval = (ushort)(System.BitConverter.ToUInt16
(_frag, 0) & 0x3FF);
//restart_interval = (ushort)(System.BitConverter.ToUInt16
(data, offset + 8) & 0x3FF);
}
return (next_fragment_offset == fragment_offset);
}
public unsafe bool Write(byte * data,
int size, out bool sync) //Write(ref byte[] data, int size,out bool sync)
{
if (Decode(data, 12))
{
for (int i = 20; i < size;)
{
buffer_ptr[_offset] = data[i++];
++_offset;
buffer_ptr[_offset] = data[i++];
++_offset;
}
size -= 20;
next_fragment_offset += size;
sync = true;
return ((data[1] >> 7) == 1);
}
/*
if (Decode(data, 12))
{
size -= 20;
Array.Copy(data, 20, buffer, _offset, size);
next_fragment_offset += size;
_offset += size;
sync = true;
return ((data[1] >> 7) == 1);
}*/
else
{
_offset = qtable.Length;
next_fragment_offset = 0;
sync = false;
return false;
}
}
public Image GetFrame(out int motion_level)
{
if (_initialized == false)
throw new Exception();
_stream_buffer = new MemoryStream(_buffer, 0, _offset, false);
_frame_img = Image.FromStream(_stream_buffer, false, true);
_offset = qtable.Length;
motion_level = 0;
next_fragment_offset = 0;
_stream_buffer.Close();
_stream_buffer.Dispose();
_stream_buffer = null;
return _frame_img;
/*stream_buffer = new MemoryStream(_offset);
stream_buffer.Write(buffer, 0, _offset); */
//stream_buffer = new MemoryStream(10);
/* GCHandle handle = GCHandle.Alloc(buffer, GCHandleType.Normal);
IntPtr ptr = Marshal.UnsafeAddrOfPinnedArrayElement(buffer, 0);
frame_img = new Bitmap(width * 8, height * 8,
(width * 8), System.Drawing.Imaging.PixelFormat.Format24bppRgb, ptr);
*/
//Console.WriteLine(frame_img.PixelFormat.ToString() +
//" " + Image.GetPixelFormatSize(frame_img.PixelFormat) / 8);
/*GC.ReRegisterForFinalize(stream_buffer);*/
//Bitmap map = frame_img as Bitmap;
//imgProceesor.CompareUnsafeFaster(out motion_level, ref frame_img);
//motion_level = imgProceesor.MotionLevel;
//Console.WriteLine("motion " + motion_level);
}
~JPEGFrame()
{
Dispose(true);
}
protected virtual void Dispose(bool isDisposing)
{
if (_alreadyDisposed)
return;
// Don't dispose more than once.
if (isDisposing)
{
// TODO: free managed resources here.
if(_frame_img != null)
_frame_img.Dispose();
if(_stream_buffer != null)
_stream_buffer.Close();
//stream_buffer.Dispose();
_initialized = false;
_frame_img = null;
_stream_buffer = null;
qtable = null;
_buffer = null;
_alreadyDisposed = true;
}
// TODO: free unmanaged resources here.
// Set disposed flag:
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(true);
}
public override string ToString()
{
string ret = "type_specific= " + type_specific + "\r\n";
ret += "fragment_offset= " + fragment_offset + "\r\n";
ret += "type=" + jpeg_type + "\r\n";
ret += "q=" + q + "\r\n";
ret += "width=" + width + "\r\n";
ret += "height=" + height;
if (jpeg_type > 63)
{
ret += "\r\n" + "restart_interval=" + restart_interval + "\r\n";
ret += "f=" + f + " l=" + l + "\r\n";
ret += "restart_count=" + restart_count;
}
return ret;
}
}
}笔记
请理解，我在2005年编写了这个代码，并没有做任何更新。 如果您认为可以重新排列代码并提供意见，请让我知道。 我也希望现有的开源项目的RTP / H.264托管API实现。
兴趣点
我有兴趣创建互联网交换点。
历史
2005年第一版
注：本篇文章值得关注的是RTP包封装和Frame数据获取。
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