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Cavern.Format/Transcoders/EnhancedAC3Body/AllocationParsing.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,125 @@ | ||
| using System; | ||
| using System.Runtime.CompilerServices; | ||
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| using Cavern.Format.Utilities; | ||
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| namespace Cavern.Format.Transcoders { | ||
| partial class EnhancedAC3Body { | ||
| // Convert bitstream data to allocation data | ||
| partial class Allocation { | ||
| /// <summary> | ||
| /// Reference exponent for decoding others with offsets (absexp). | ||
| /// </summary> | ||
| public int absoluteExponent; | ||
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| /// <summary> | ||
| /// Grouped exponents read from the bitstream (gexp/exps). A 7-bit encoded exponent data contains 3 consecutive exponents. | ||
| /// </summary> | ||
| /// <remarks>Handling of this array differs from the reference code, | ||
| /// the first element is extracted to <see cref="absoluteExponent"/>.</remarks> | ||
| public readonly int[] groupedExponents; | ||
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| /// <summary> | ||
| /// Fully decoded, final exponents, used for shifting mantissas to place (exp). | ||
| /// </summary> | ||
| public readonly int[] exponents; | ||
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| /// <summary> | ||
| /// Exponents mapped for power spectral density. | ||
| /// </summary> | ||
| public readonly int[] psd; | ||
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| /// <summary> | ||
| /// PSD summed for each masked band (bndpsd). | ||
| /// </summary> | ||
| public readonly int[] integratedPSD; | ||
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| /// <summary> | ||
| /// Read grouped full-range channel exponent data from the bitstream and decode it. | ||
| /// </summary> | ||
| public void ReadChannelExponents(BitExtractor extractor, ExpStrat expstr, int nchgrps) { | ||
| ReadExponents(extractor, nchgrps); | ||
| extractor.Skip(2); // This is gainrng, telling the max gain as 1/(2^gainrng). It's useless. | ||
| UngroupExponents(nchgrps, expstr, 0, 1); | ||
| } | ||
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| /// <summary> | ||
| /// Read grouped coupling channel exponent data from the bitstream and decode it. | ||
| /// </summary> | ||
| public void ReadCouplingExponents(BitExtractor extractor, ExpStrat expstr, int startMantissa, int ncplgrps) { | ||
| ReadExponents(extractor, ncplgrps); | ||
| absoluteExponent <<= 1; | ||
| UngroupExponents(ncplgrps, expstr, startMantissa, startMantissa); | ||
| } | ||
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| /// <summary> | ||
| /// Read grouped LFE exponent data from the bitstream and decode it. | ||
| /// </summary> | ||
| public void ReadLFEExponents(BitExtractor extractor) { | ||
| absoluteExponent = extractor.Read(4); | ||
| groupedExponents[0] = extractor.Read(7); | ||
| groupedExponents[1] = extractor.Read(7); | ||
| UngroupExponents(nlfegrps, ExpStrat.D15, lfestrtmant, lfestrtmant + 1); | ||
| } | ||
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| /// <summary> | ||
| /// Read the grouped exponents from the bitstream. | ||
| /// </summary> | ||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| void ReadExponents(BitExtractor extractor, int ngrps) { | ||
| absoluteExponent = extractor.Read(4); | ||
| for (int group = 0; group < ngrps; group++) { | ||
| groupedExponents[group] = extractor.Read(7); | ||
| } | ||
| } | ||
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| /// <summary> | ||
| /// Ungroup what's grouped in <see cref="groupedExponents"/>, decode the differential coding, | ||
| /// and calculate power spectral density values. | ||
| /// </summary> | ||
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| void UngroupExponents(int ngrps, ExpStrat expstr, int startMantissa, int exponentOffset) { | ||
| // Ungrouping and decoding exponents | ||
| int grpsize = expstr != ExpStrat.D45 ? (int)expstr : 4, | ||
| absexp = absoluteExponent, // Rolling differential decoding value (dexp in the reference code) | ||
| endMantissa = exponentOffset; | ||
| exponents[0] = absexp; | ||
| for (int grp = 0; grp < ngrps; grp++) { | ||
| int expacc = groupedExponents[grp]; | ||
| absexp += expacc / 25 - 2; // Ungroup and unbias mapped values in the same step | ||
| for (int j = 0; j < grpsize; j++) { | ||
| exponents[endMantissa++] = absexp; | ||
| } | ||
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| absexp += expacc % 25 / 5 - 2; | ||
| for (int j = 0; j < grpsize; j++) { | ||
| exponents[endMantissa++] = absexp; | ||
| } | ||
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| absexp += expacc % 5 - 2; | ||
| for (int j = 0; j < grpsize; j++) { | ||
| exponents[endMantissa++] = absexp; | ||
| } | ||
| } | ||
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| // Exponent mapping into PSD | ||
| for (int bin = startMantissa; bin < endMantissa; bin++) { | ||
| psd[bin] = 3072 - (exponents[bin] << 7); | ||
| } | ||
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| // PSD integration | ||
| int i = startMantissa, | ||
| k = masktab[startMantissa], | ||
| lastbin; | ||
| do { | ||
| lastbin = Math.Min(bndtab[k], endMantissa); | ||
| integratedPSD[k] = psd[i++]; | ||
| while (i < lastbin) { | ||
| integratedPSD[k] = LogAdd(integratedPSD[k], psd[i++]); | ||
| } | ||
| k++; | ||
| } while (endMantissa > lastbin); | ||
| } | ||
| } | ||
| } | ||
| } |
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