在上一篇FLV文件格式解析中，我们对FLV的文件结构有了一定了解，现在我们就可以对FLV文件解析解析了。我这里用的是c#，只要理解了过程java、c++都是可以的。
废话少说，先上效果图：
1.工具类
在解析的过程中，我们会和byte做各种运算，所以我定义了一个byte工具类ByteUtils：
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.IO;namespace FLVParer.Utils{ class ByteUtils { public static uint ByteToUInt(byte[] bs, int length) { if (bs == null || bs.Length < length) return 0; uint rtn = 0; for (int i = 0; i < length; i++) { rtn <<= 8; rtn |= bs[i]; } return rtn; } public static double ByteToDouble(byte[] bs) { if (bs == null || bs.Length < 8) return 0; byte[] b2 = new byte[8]; for (int i = 0; i < 8; i++) { b2[i] = bs[7 - i]; } return BitConverter.ToDouble(b2, 0); } public static short ReadUI16(Stream src) { byte[] bs = new byte[2]; if (src.Read(bs, 0, 2) <= 0) return 0; return (short)((bs[0] << 8) | bs[1]); } public static uint ReadUI24(Stream src) { byte[] bs = new byte[3]; if (src.Read(bs, 0, 3) <= 0) throw new IOException("Stream end."); return ByteToUInt(bs, 3); } public static uint ReadUI32(Stream src) { byte[] bs = new byte[4]; if (src.Read(bs, 0, 4) <= 0) throw new IOException("Stream end."); return ByteToUInt(bs, 4); } public static string GetTime(uint time) { return (time / 60000).ToString() + ":" + (time / 1000 % 60).ToString("D2") + "." + (time % 1000).ToString("D3"); } }}
2.FLV类
FLV类，主要的类，里面包括一个header和许多的tag，也就是一个FLV文件的结构：
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.IO;using FLVParer.Utils;namespace FLVParer.Model{ class FLV { public Header header { get; private set; } List<Tag> tags; public FLV(Stream stream) { header = new Header(); header.readHeader(stream); stream.Seek(header.size, SeekOrigin.Begin); tags = new List<Tag>(); while (stream.Position < stream.Length-4) { tags.Add(readTag(stream)); } } private Tag readTag(Stream stream) { Tag tag = null; byte[] buf = new byte[4]; stream.Read(buf, 0, 4); int type = stream.ReadByte(); switch (type) { case 8: tag = new AudioTag(); break; case 9: tag = new VideoTag(); break; case 18: tag = new ScriptTag(); break; } tag.presize = ByteUtils.ByteToUInt(buf, 4); tag.datasize = ByteUtils.ReadUI24(stream); tag.timestamp = ByteUtils.ReadUI24(stream); tag.timestamp_ex = stream.ReadByte(); tag.streamid = ByteUtils.ReadUI24(stream); tag.readData(stream); return tag; } }}
2.1.Header类
Header类，保存FLV文件的头信息：
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.IO;using FLVParer.Utils;namespace FLVParer.Model{ class Header { public String type { get; private set; } public int version { get; private set; } public bool hasVideo { get; private set; } public bool hasAudio { get; private set; } public uint size { get; private set; } public void readHeader(Stream stream) { byte[] buf = new byte[4]; stream.Read(buf, 0, 3); type = Encoding.Default.GetString(buf); stream.Read(buf, 0, 1); version = buf[0]; stream.Read(buf, 0, 1); buf[0] &= 0x0f; if ((buf[0] & 0x01) == 1) { hasVideo = true; } if ((buf[0] & 0x04) == 4) { hasAudio = true; } stream.Read(buf, 0, 4); size = ByteUtils.ByteToUInt(buf, 4); } }}
2.2.Tag类
Tag类是一个抽象类，因为tag的种类有三种，为了统一管理，抽象出Tag类：
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.IO;namespace FLVParer.Model{ enum TagType { video, audio, Script } abstract class Tag { public TagType tagType;//tag类型 public uint presize;//前一tag大小 public uint datasize;//数据区大小 public uint timestamp; //时间戳 单位ms public int timestamp_ex;//时间戳扩展 public uint streamid;//ID public long offset;//偏移量 public byte[] data;//数据 //对tag进行读取 public abstract void readData(Stream stream); }}
2.2.1.ScriptTag类
脚本tag类，继承自Tag类，并添加成员变量Values，用于保存脚本信息：
using System.Collections.Generic;using System.Text;using System.IO;using FLVParer.Utils;namespace FLVParer.Model{ class ScriptTag : Tag { public List<KeyValuePair<string, object>> Values { get; private set; } public ScriptTag() { tagType = TagType.Script; Values = new List<KeyValuePair<string, object>>(); } public override void readData(Stream stream) { offset = 0; Values.Clear(); byte[] bs = new byte[3]; while (offset < this.datasize) { stream.Read(bs, 0, 3); if (bs[0] == 0 && bs[1] == 0 && bs[2] == 9) { offset += 3; break; } stream.Seek(-3, SeekOrigin.Current); AddElement("#" + offset, ReadElement(stream)); } } private void AddElement(string key, object o) { Values.Add(new KeyValuePair<string, object>(key, o)); } private object ReadElement(Stream src) { int type = src.ReadByte(); offset++; switch (type) { case 0: // Number - 8 return ReadDouble(src); case 1: // Boolean - 1 return ReadByte(src); case 2: // String - 2+n return ReadString(src); case 3: // Object return ReadObject(src); case 4: // MovieClip return ReadString(src); case 5: // Null break; case 6: // Undefined break; case 7: // Reference - 2 return ReadUShort(src); case 8: // ECMA array return ReadArray(src); case 10: // Strict array return ReadStrictArray(src); case 11: // Date - 8+2 return ReadDate(src); case 12: // Long string - 4+n return ReadLongString(src); } return null; } private object ReadObject(Stream src) { byte[] bs = new byte[3]; ScriptObject obj = new ScriptObject(); while (offset < this.datasize) { src.Read(bs, 0, 3); if (bs[0] == 0 && bs[1] == 0 && bs[2] == 9) { offset += 3; break; } src.Seek(-3, SeekOrigin.Current); string key = ReadString(src); if (key[0] == 0) break; obj[key] = ReadElement(src); } return obj; } private double ReadDate(Stream src) { double d = ReadDouble(src); src.Seek(2, SeekOrigin.Current); offset += 2; return d; } private ScriptObject ReadArray(Stream src) { byte[] buffer = new byte[4]; src.Read(buffer, 0, 4); offset += 4; uint count = ByteUtils.ByteToUInt(buffer, 4); ScriptObject array = new ScriptObject(); for (uint i = 0; i < count; i++) { string key = ReadString(src); array[key] = ReadElement(src); } src.Seek(3, SeekOrigin.Current); // 00 00 09 offset += 3; return array; } private ScriptArray ReadStrictArray(Stream src) { byte[] bs = new byte[4]; src.Read(bs, 0, 4); offset += 4; ScriptArray array = new ScriptArray(); uint count = ByteUtils.ByteToUInt(bs, 4); for (uint i = 0; i < count; i++) { array.Add(ReadElement(src)); } return array; } private double ReadDouble(Stream src) { byte[] buffer = new byte[8]; src.Read(buffer, 0, 8); offset += 8; return ByteUtils.ByteToDouble(buffer); } private byte ReadByte(Stream src) { offset++; return (byte)src.ReadByte(); } private string ReadString(Stream src) { byte[] bs = new byte[2]; src.Read(bs, 0, 2); offset += 2; int n = (int)ByteUtils.ByteToUInt(bs, 2); bs = new byte[n]; src.Read(bs, 0, n); offset += n; return Encoding.ASCII.GetString(bs); } private string ReadLongString(Stream src) { byte[] bs = new byte[4]; src.Read(bs, 0, 4); offset += 4; int n = (int)ByteUtils.ByteToUInt(bs, 4); bs = new byte[n]; src.Read(bs, 0, n); offset += n; return Encoding.ASCII.GetString(bs); } private ushort ReadUShort(Stream src) { byte[] buffer = new byte[2]; src.Read(buffer, 0, 2); offset += 2; return (ushort)ByteUtils.ByteToUInt(buffer, 2); } } public class ScriptObject { public static int indent = 0; private Dictionary<string, object> values = new Dictionary<string, object>(); public object this[string key] { get { object o; values.TryGetValue(key, out o); return o; } set { if (!values.ContainsKey(key)) { values.Add(key, value); } } } public override string ToString() { string str = "{\r\n"; ScriptObject.indent += 2; foreach (KeyValuePair<string, object> kv in values) { str += new string(' ', ScriptObject.indent) + kv.Key + ": " + kv.Value + "\r\n"; } ScriptObject.indent -= 2; //if (str.Length > 1) // str = str.Substring(0, str.Length - 1); str += "}"; return str; } } public class ScriptArray { private List values = new List(); public object this[int index] { get { if (index >= 0 && index < values.Count) return values[index]; return null; } } public void Add(object o) { values.Add(o); } public override string ToString() { string str = "["; int n = 0; foreach (object o in values) { if (n % 10 == 0) str += "\r\n"; n++; str += o + ","; } if (str.Length > 1) str = str.Substring(0, str.Length - 1); str += "\r\n]"; return str; } }}
2.2.2.VideoTag类
视频tag类：
using System.IO;namespace FLVParer.Model{ class VideoTag : Tag { public int frameType;//帧类型 public int encodeID;//编码ID public VideoTag() { tagType = TagType.video; } public override void readData(Stream stream) { int info = stream.ReadByte(); frameType = info >> 4; encodeID = info & 0x0f; data = new byte[datasize - 1]; stream.Read(data, 0, (int)datasize - 1); } }}
2.2.3.AudioTag 类
音频tag类：
using System.IO;namespace FLVParer.Model{ class AudioTag : Tag { public int formate;//音频格式 public int rate;//采样率 public int size;//采样的长度 public int type;//音频类型 public AudioTag() { tagType = TagType.audio; } public override void readData(Stream stream) { int info = stream.ReadByte(); formate = info >> 4; rate = (info & 0x0c) >> 2; size = (info & 0x02) >> 1; type = info & 0x01; data = new byte[datasize - 1]; stream.Read(data, 0, (int)datasize - 1); } }}
3.使用方法
用法很简单，new出来的时候把FLV文件的stream对象传进去就行了，比如我这样的：
FLV flv = null;using (FileStream fs = new FileStream("t31_stract.flv", FileMode.Open, FileAccess.Read)){ flv = new FLV(fs);}
之后就可以使用flv对象来分析当前flv的信息了。