Audio

前陣子，在工作上剛好需要對 wav 檔案格式進行判定，可是 NAudio 製作出來的格式用來作判斷又有錯誤，所以土法煉鋼寫了一個小 class：

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

class WavInfo
{
    private String _Error;
    public String Error
    {
        get
        {
            return this._Error;
        }
    }

    private Boolean _PCM;
    public Boolean PCM
    {
        get
        {
            return this._PCM;
        }
    }

    private uint _Channel;
    public uint Channel
    {
        get
        {
            return this._Channel;
        }
    }

    private uint _SampleRate;
    public uint SampleRate
    {
        get
        {
            return this._SampleRate;
        }
    }

    private uint _BitsPerSample;
    public uint BitsPerSample
    {
        get
        {
            return this._BitsPerSample;
        }
    }

    private uint _ByteRate;
    public uint ByteRate
    {
        get
        {
            return this._ByteRate;
        }
    }

    private uint _BlockAlign;
    public uint BlockAlign
    {
        get
        {
            return this._BlockAlign;
        }
    }

    public WavInfo(String FileName)
    {
        try
        {
            FileStream FS = File.OpenRead(@FileName);
            Byte[] ReadTmp = new Byte[36];

            FS.Read(ReadTmp, 0, 36);
            FS.Close();

            if (BitConverter.ToUInt16(ReadTmp, 20) == 1)
            {
                this._PCM = true;
            }

            this._Channel = BitConverter.ToUInt16(ReadTmp, 22);
            this._SampleRate = BitConverter.ToUInt32(ReadTmp, 24);
            this._BitsPerSample = BitConverter.ToUInt16(ReadTmp, 34);

            this._ByteRate = this._Channel * this._SampleRate * this._BitsPerSample / 8;
            this._BlockAlign = this._Channel * this._BitsPerSample / 8;

            this._Error = String.Empty;
        }
        catch (Exception e)
        {
             this._Error = e.ToString();
        }
    }
}

• 檢查 Error 是否為空字串，就知道是否成功取得 wav 檔案資訊。
• 檢查 PCM 是否為 true，就知道該檔案是不是 PCM 格式的 wav 檔。
• wav 檔播放的時間會等於 ByteRate。