37 lines
1.3 KiB
C#
37 lines
1.3 KiB
C#
/*
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* NLayer - A C# MPEG1/2/2.5 audio decoder
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*
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*/
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using System;
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namespace NLayer.Decoder
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{
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// Layer I is really just a special case of Layer II... 1 granule, 4 allocation bits per subband, 1 scalefactor per active subband, no grouping
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// That (of course) means we literally have no logic here
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class LayerIDecoder : LayerIIDecoderBase
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{
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static internal bool GetCRC(MpegFrame frame, ref uint crc)
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{
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return LayerIIDecoderBase.GetCRC(frame, _rateTable, _allocLookupTable, false, ref crc);
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}
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// this is simple: all 32 subbands have a 4-bit allocations, and positive allocation values are {bits per sample} - 1
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static readonly int[] _rateTable = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
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static readonly int[][] _allocLookupTable = { new int[] { 4, 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 } };
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internal LayerIDecoder() : base(_allocLookupTable, 1) { }
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protected override int[] GetRateTable(IMpegFrame frame)
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{
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return _rateTable;
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}
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protected override void ReadScaleFactorSelection(IMpegFrame frame, int[][] scfsi, int channels)
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{
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// this is a no-op since the base logic uses "2" as the "has energy" marker
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}
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}
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}
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