54 lines
1.9 KiB
Go
54 lines
1.9 KiB
Go
package amrnb
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// Closed-loop long-term-prediction (adaptive codebook) step, ported from
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// opencore-amrnb cl_ltp.cpp. clLtp runs the fractional pitch search (pitchFr),
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// builds the adaptive codebook (predLt), filters it (convolve), computes the
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// pitch gain (gPitch) with mode-specific clamping (and MR122 quantization), then
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// forms the codebook-search target xn2 = xn - gain·y1 and updates res2. The
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// tone-stabilization gain clip (gpc_flag) is not applied (active-speech path).
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// Bit-exact with the reference for that path.
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const cGP_CLIP = 15565 // 0.95 Q14 pitch-gain clip
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type clLtpResult struct {
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T0, T0frac int16
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gainPit int16
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gpLimit int16
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gCoeff [5]int16
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pitchIndex int16
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gainPitIndex int16 // MR122 only
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hasGainPitIndex bool
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}
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// clLtp performs the adaptive-codebook analysis for one subframe. exc[excOff] is
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// the current subframe; predLt writes it in place. xn2 (codebook target) and
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// res2 (residual) are written. Mirrors cl_ltp.
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func (st *pitchFrState) clLtp(mode, frameOffset int, Top, h1, exc []int16, excOff int, res2, xn, xn2, yl []int16) clLtpResult {
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var r clLtpResult
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resu3 := int16(0)
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r.T0, r.T0frac, resu3, r.pitchIndex = st.pitchFr(mode, Top, exc, excOff, xn, h1, cL_SUBFR, frameOffset)
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predLt(exc, excOff, r.T0, r.T0frac, cL_SUBFR, resu3)
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convolve(exc[excOff:], h1, yl, cL_SUBFR)
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r.gainPit = gPitch(mode, xn, yl, r.gCoeff[:], cL_SUBFR)
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r.gpLimit = maxInt16 // tone-stabilization clip disabled
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if mode == dMR475 || mode == dMR515 {
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if r.gainPit > 13926 {
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r.gainPit = 13926
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}
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} else if mode == dMR122 {
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var cand, cind [3]int16
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r.gainPitIndex = qGainPitch(dMR122, r.gpLimit, &r.gainPit, cand[:], cind[:])
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r.hasGainPitIndex = true
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}
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g := r.gainPit
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for i := 0; i < cL_SUBFR; i++ {
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xn2[i] = xn[i] - int16((int32(yl[i])*int32(g))>>14)
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res2[i] -= int16((int32(exc[excOff+i]) * int32(g)) >> 14)
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}
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return r
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}
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