/// <summary>
/// コンストラクタ
/// </summary>
/// <param name="offset">フレームのバイトオフセット</param>
public AdtsFrameInfo(AacAdtsHeader hdr, long offset)
{
// 1 aac frame is 1024 samples
// AAC files always have 1024 samples per frame.
// In MP4 files it can be 960 too,
// 1024 samples per frame, per channel
Header = hdr;
Offset = offset;
Duration = 1024.0 / Header.SamplingRate;
Bps = Header.FrameSize * 8 / Duration;
}
/// <summary>
/// ストリームパーシング処理本体
/// </summary>
/// <param name="br">バイナリ読み込みオブジェクト</param>
/// <param name="remain">読み取り可能なバイトサイズ</param>
/// <returns></returns>
private dynamic parse(BinaryReader br, long remain)
{
while (remain > 7)
{
// ヘッダー分読み込む
long offset = br.BaseStream.Position;
byte[] b = br.ReadBytes(7);
var hdr = new AacAdtsHeader();
// Sync Header
if (b[0] != 0xFF && (b[1] & 0xF0) != 0xF0)
{
System.Diagnostics.Debug.WriteLine("error");
return(new { Result = 1, Remain = remain });
}
// ID
hdr.ID = ((b[1] & 0x08) == 0x08);
// Layer, 常に0
if ((b[1] & 0x06) != 0)
{
System.Diagnostics.Debug.WriteLine("error");
return(new { Result = 2, Remain = remain });
}
// Protection bit
hdr.ProtectionBit = ((b[1] & 0x01) == 0x01);
// Profile
hdr.Profile = (byte)((b[2] >> 6) & 0x03);
// Fs
hdr.Fs = (byte)((b[2] >> 2) & 0x0F);
// PrivateBit
hdr.PrivateBit = ((b[2] & 0x02) == 0x02);
byte tmp = (byte)(b[2] & 0x01);
tmp <<= 2;
tmp |= (byte)((b[3] >> 6) & 0x3);
hdr.Channel = tmp;
// オリジナル
hdr.Original = ((b[3] & 0x20) == 0x20);
hdr.Home = ((b[3] & 0x10) == 0x10);
hdr.Copyright = ((b[3] & 0x08) == 0x08);
hdr.Icopyright = ((b[3] & 0x04) == 0x04);
// フレームサイズ
UInt16 size = (byte)(b[3] & 0x03);
size <<= 8;
size |= b[4];
size <<= 3;
size |= (UInt16)(b[5] >> 5);
hdr.FrameSize = (Int16)size;
// バッファサイズ
size = (byte)(b[5] & 0x1F);
size <<= 6;
size |= (UInt16)((b[6] >> 2) & 0x3F);
hdr.BufferSize = (Int16)size;
// オフセット
hdr.DBOffset = (byte)(b[6] & 0x03);
if (!hdr.ProtectionBit)
{
hdr.CRC = br.ReadUInt16();
}
// 保存
AdtsFrameInfo fi = new AdtsFrameInfo(hdr, offset);
m_List.Add(fi);
// 移動
br.BaseStream.Seek(offset + hdr.FrameSize, SeekOrigin.Begin);
remain -= hdr.FrameSize;
}
return(new { Result = 0, Remain = remain });
}
