alac

# # Original C(++) version by Apple, http://alac.macosforge.org/ # # Javascript port by Jens Nockert and Devon Govett of OFMLabs, https://github.com/ofmlabs/alac.js # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # # File: ag_dec.coffee # Contains: Adaptive Golomb decode routines. class Aglib PB0 = 40 MB0 = 10 KB0 = 14 MAX_RUN_DEFAULT = 255 MAX_PREFIX_16 = 9 MAX_PREFIX_32 = 9 QBSHIFT = 9 QB = 1 << QBSHIFT MMULSHIFT = 2 MDENSHIFT = QBSHIFT - MMULSHIFT - 1 MOFF = 1 << (MDENSHIFT-2) N_MAX_MEAN_CLAMP = 0xFFFF N_MEAN_CLAMP_VAL = 0xFFFF MMULSHIFT = 2 BITOFF = 24 MAX_DATATYPE_BITS_16 = 16 lead = (input) -> output = 0 curbyte = 0 while true # emulate goto :) curbyte = input >>> 24 break if curbyte output += 8 curbyte = input >>> 16 break if curbyte & 0xff output += 8 curbyte = input >>> 8 break if curbyte & 0xff output += 8 curbyte = input break if curbyte & 0xff output += 8 return output if curbyte & 0xf0 curbyte >>>= 4 else output += 4 if curbyte & 0x8 return output if curbyte & 0x4 return output + 1 if curbyte & 0x2 return output + 2 if curbyte & 0x1 return output + 3 # shouldn't get here return output + 4 dyn_get_16 = (data, m, k) -> offs = data.bitPosition stream = data.peek(32 - offs) << offs bitsInPrefix = lead(~stream) if bitsInPrefix >= MAX_PREFIX_16 data.advance(MAX_PREFIX_16 + MAX_DATATYPE_BITS_16) stream <<= MAX_PREFIX_16 result = (stream >>> (32 - MAX_DATATYPE_BITS_16)) else data.advance(bitsInPrefix + k) stream <<= (bitsInPrefix + 1) v = (stream >>> (32 - k)) result = bitsInPrefix * m + v - 1 if v < 2 result -= (v - 1) else data.advance(1) return result dyn_get_32 = (data, m, k, maxbits) -> offs = data.bitPosition stream = data.peek(32 - offs) << offs result = lead(~stream) if result >= MAX_PREFIX_32 data.advance(MAX_PREFIX_32) return data.read(maxbits) else data.advance(result + 1) if k isnt 1 stream <<= (result + 1) result *= m v = (stream >>> (32 - k)) data.advance(k - 1) if v > 1 result += v - 1 data.advance(1) return result @ag_params: (m, p, k, f, s, maxrun) -> mb: m mb0: m pb: p kb: k wb: (1 << k) - 1 qb: QB - p fw: f sw: s maxrun: maxrun @dyn_decomp: (params, data, pc, samples, maxSize) -> {pb, kb, wb, mb0:mb} = params zmode = 0 c = 0 while c < samples m = mb >>> QBSHIFT k = Math.min(31 - lead(m + 3), kb) m = (1 << k) - 1 n = dyn_get_32(data, m, k, maxSize) # least significant bit is sign bit ndecode = n + zmode multiplier = -(ndecode & 1) | 1 pc[c++] = ((ndecode + 1) >>> 1) * multiplier mb = pb * (n + zmode) + mb - ((pb * mb) >> QBSHIFT) # update mean tracking if n > N_MAX_MEAN_CLAMP mb = N_MEAN_CLAMP_VAL zmode = 0 if ((mb << MMULSHIFT) < QB) && (c < samples) zmode = 1 k = lead(mb) - BITOFF + ((mb + MOFF) >> MDENSHIFT) mz = ((1 << k) - 1) & wb n = dyn_get_16(data, mz, k) unless c + n <= samples return false for j in [0...n] by 1 pc[c++] = 0 zmode = 0 if n >= 65535 mb = 0 return true module.exports = Aglib