/// <summary>
/// 获取标签帧长度
/// </summary>
/// <returns></returns>
private void GetTAGFrameLength()
{
//必须为"ID3"否则认为标签不存在
byte[] mp3Header = MP3Buffer.GetRange(0, 3).ToArray();
//MP3Stream.Read(mp3Header, 0, mp3Header.Length);
if (Encoding.ASCII.GetString(mp3Header) != "ID3")
{
throw new NotImplementedException("暂只能识别ID3的MP3音频");
}
//版本号 ID3V2.3 就记录 3
byte ver = MP3Buffer[3];
//副版本号此版本记录为
byte Revision = MP3Buffer[4];
//存放标志的字节,这个版本只定义了三位
byte flag = MP3Buffer[5];
//标签大小,包括标签头的 10 个字节和所有的标签帧的大小
byte[] size = MP3Buffer.GetRange(6, 4).ToArray();
//MP3Stream.Read(size, 0, size.Length);
MP3Buffer.RemoveRange(0, 10);
TAGFrameLength = (size[0] & 0x7F) * 0x200000 + (size[1] & 0x7F) * 0x400 + (size[2] & 0x7F) * 0x80
+ (size[3] & 0x7F);
}
/// <summary>
/// 获取标签帧
/// </summary>
/// <returns></returns>
public byte[] GetTAGFrame()
{
GetTAGFrameLength();
byte[] frameBuffer = MP3Buffer.GetRange(0, TAGFrameLength).ToArray();
MP3Buffer.RemoveRange(0, TAGFrameLength);
//MP3Stream.Read(frameBuffer, 0, frameBuffer.Length);
return(frameBuffer);
}
/// <summary>
/// 获取数据帧长度
/// </summary>
/// <returns></returns>
private int GetAuidoFrameLength(out double playTime)
{
playTime = 0;
byte[] headerBuffer = MP3Buffer.GetRange(0, 4).ToArray();
//MP3Stream.Read(headerBuffer, 0, headerBuffer.Length);
////读取位置回到ff fb
//MP3Stream.Position = MP3Stream.Position - 4;
if (headerBuffer[0] != 0xFF)
{
Console.WriteLine("没有读取到FF头");
return(0);
}
MP3AudioFrameHeader header = new MP3AudioFrameHeader(headerBuffer);
int length = 0;
//每帧采样数
int frameCount = FrameCountDictionary[header.Version][header.Layer];
//比特率
int kbps = KBPSDictionary[header.Version][header.Layer][header.BitrateIndex];
//采样率
double khz = KHZDictionary[header.Version][header.SamplingFrequency];
switch (header.Layer)
{
//11 -> Layer 1, L1
case "11":
break;
//10 -> Layer 2, L2
//01 -> Layer 3, L3
case "10":
case "01":
length = (int)Math.Floor(((frameCount / 8 * kbps) / khz)) + (header.Padding == "0" ? 0 : 1);
playTime = frameCount / khz;
break;
default:
break;
}
return(length);
}
public byte[] GetAudioFrame(out double playTime)
{
playTime = 0;
if (MP3Buffer.Count == 0)
{
return(new byte[0]);
}
int audioFrameLength = GetAuidoFrameLength(out playTime);
if (audioFrameLength == 0)
{
return(new byte[0]);
}
byte[] audioBuffer = MP3Buffer.GetRange(0, audioFrameLength).ToArray();
//MP3Stream.Read(audioBuffer, 0, audioFrameLength);
MP3Buffer.RemoveRange(0, audioFrameLength);
return(audioBuffer);
}
