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: dp_dec.coffee # Contains: Dynamic Predictor decode routines class Dplib copy = (dst, dstOffset, src, srcOffset, n) -> destination = new Uint8Array(dst, dstOffset, n) source = new Uint8Array(src, srcOffset, n) destination.set(source) return dst @unpc_block: (pc1, out, num, coefs, active, chanbits, denshift) -> chanshift = 32 - chanbits denhalf = 1 << (denshift - 1) out[0] = pc1[0]; # just copy if active is 0 if active is 0 return copy(out, 0, pc1, 0, num * 4) # short-circuit if active is 31 if active is 31 prev = out[0] for i in [1...num] by 1 del = pc1[i] + prev prev = (del << chanshift) >> chanshift out[i] = prev return for i in [1..active] by 1 del = pc1[i] + out[i - 1] out[i] = (del << chanshift) >> chanshift lim = active + 1 if active is 4 # Optimization for active == 4 [a0, a1, a2, a3] = coefs for j in [lim...num] by 1 top = out[j - lim] offset = j - 1 b0 = top - out[offset] b1 = top - out[offset - 1] b2 = top - out[offset - 2] b3 = top - out[offset - 3] sum1 = (denhalf - a0 * b0 - a1 * b1 - a2 * b2 - a3 * b3) >> denshift del = del0 = pc1[j] sg = (-del >>> 31) | (del >> 31) del += top + sum1 out[j] = (del << chanshift) >> chanshift if sg > 0 sgn = (-b3 >>> 31) | (b3 >> 31) a3 -= sgn del0 -= 1 * ((sgn * b3) >> denshift) continue if del0 <= 0 sgn = (-b2 >>> 31) | (b2 >> 31) a2 -= sgn del0 -= 2 * ((sgn * b2) >> denshift) continue if del0 <= 0 sgn = (-b1 >>> 31) | (b1 >> 31) a1 -= sgn del0 -= 3 * ((sgn * b1) >> denshift) continue if del0 <= 0 a0 -= (-b0 >>> 31) | (b0 >> 31) else if sg < 0 # note: to avoid unnecessary negations, we flip the value of "sgn" sgn = -((-b3 >>> 31) | (b3 >> 31)) a3 -= sgn del0 -= 1 * ((sgn * b3) >> denshift) continue if del0 >= 0 sgn = -((-b2 >>> 31) | (b2 >> 31)) a2 -= sgn del0 -= 2 * ((sgn * b2) >> denshift) continue if del0 >= 0 sgn = -((-b1 >>> 31) | (b1 >> 31)) a1 -= sgn del0 -= 3 * ((sgn * b1) >> denshift) continue if del0 >= 0 a0 += (-b0 >>> 31) | (b0 >> 31) coefs[0] = a0 coefs[1] = a1 coefs[2] = a2 coefs[3] = a3 else if active is 8 # Optimization for active == 8 [a0, a1, a2, a3, a4, a5, a6, a7] = coefs for j in [lim...num] by 1 top = out[j - lim] offset = j - 1 b0 = top - out[offset] b1 = top - out[offset - 1] b2 = top - out[offset - 2] b3 = top - out[offset - 3] b4 = top - out[offset - 4] b5 = top - out[offset - 5] b6 = top - out[offset - 6] b7 = top - out[offset - 7] sum1 = (denhalf - a0 * b0 - a1 * b1 - a2 * b2 - a3 * b3 - a4 * b4 - a5 * b5 - a6 * b6 - a7 * b7) >> denshift del = del0 = pc1[j] sg = (-del >>> 31) | (del >> 31) del += top + sum1 out[j] = (del << chanshift) >> chanshift if sg > 0 sgn = (-b7 >>> 31) | (b7 >> 31) a7 -= sgn del0 -= 1 * ((sgn * b7) >> denshift) continue if del0 <= 0 sgn = (-b6 >>> 31) | (b6 >> 31) a6 -= sgn del0 -= 2 * ((sgn * b6) >> denshift) continue if del0 <= 0 sgn = (-b5 >>> 31) | (b5 >> 31) a5 -= sgn del0 -= 3 * ((sgn * b5) >> denshift) continue if del0 <= 0 sgn = (-b4 >>> 31) | (b4 >> 31) a4 -= sgn del0 -= 4 * ((sgn * b4) >> denshift) continue if del0 <= 0 sgn = (-b3 >>> 31) | (b3 >> 31) a3 -= sgn del0 -= 5 * ((sgn * b3) >> denshift) continue if del0 <= 0 sgn = (-b2 >>> 31) | (b2 >> 31) a2 -= sgn del0 -= 6 * ((sgn * b2) >> denshift) continue if del0 <= 0 sgn = (-b1 >>> 31) | (b1 >> 31) a1 -= sgn del0 -= 7 * ((sgn * b1) >> denshift) continue if del0 <= 0 a0 -= (-b0 >>> 31) | (b0 >> 31) else if sg < 0 # note: to avoid unnecessary negations, we flip the value of "sgn" sgn = -((-b7 >>> 31) | (b7 >> 31)) a7 -= sgn del0 -= 1 * ((sgn * b7) >> denshift) continue if del0 >= 0 sgn = -((-b6 >>> 31) | (b6 >> 31)) a6 -= sgn del0 -= 2 * ((sgn * b6) >> denshift) continue if del0 >= 0 sgn = -((-b5 >>> 31) | (b5 >> 31)) a5 -= sgn del0 -= 3 * ((sgn * b5) >> denshift) continue if del0 >= 0 sgn = -((-b4 >>> 31) | (b4 >> 31)) a4 -= sgn del0 -= 4 * ((sgn * b4) >> denshift) continue if del0 >= 0 sgn = -((-b3 >>> 31) | (b3 >> 31)) a3 -= sgn del0 -= 5 * ((sgn * b3) >> denshift) continue if del0 >= 0 sgn = -((-b2 >>> 31) | (b2 >> 31)) a2 -= sgn del0 -= 6 * ((sgn * b2) >> denshift) continue if del0 >= 0 sgn = -((-b1 >>> 31) | (b1 >> 31)) a1 -= sgn del0 -= 7 * ((sgn * b1) >> denshift) continue if del0 >= 0 a0 += (-b0 >>> 31) | (b0 >> 31) coefs[0] = a0 coefs[1] = a1 coefs[2] = a2 coefs[3] = a3 coefs[4] = a4 coefs[5] = a5 coefs[6] = a6 coefs[7] = a7 else # General case for i in [lim...num] by 1 sum1 = 0 top = out[i - lim] offset = i - 1 for j in [0 ... active] by 1 sum1 += coefs[j] * (out[offset - j] - top) del = del0 = pc1[i] sg = (-del >>> 31) | (del >> 31) del += top + ((sum1 + denhalf) >> denshift) out[i] = (del << chanshift) >> chanshift if sg > 0 for j in [active - 1 .. 0] by -1 dd = top - out[offset - j] sgn = (-dd >>> 31) | (dd >> 31) coefs[j] -= sgn del0 -= (active - j) * ((sgn * dd) >> denshift) break if del0 <= 0 else if sg < 0 for j in [active - 1 .. 0] by -1 dd = top - out[offset - j] sgn = (-dd >>> 31) | (dd >> 31) coefs[j] += sgn del0 -= (active - j) * ((-sgn * dd) >> denshift) break if del0 >= 0 return module.exports = Dplib