/*

 * Copyright (c) 2007-2008 CSIRO

 * Copyright (c) 2007-2009 Xiph.Org Foundation

 * Copyright (c) 2008-2009 Gregory Maxwell

 * Copyright (c) 2012 Andrew D'Addesio

 * Copyright (c) 2013-2014 Mozilla Corporation

 * Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@gmail.com>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include <float.h>

#include "config_components.h"

#include "libavutil/mem.h"

#include "mathops.h"

#include "tab.h"

#include "pvq.h"

#define ROUND_MUL16(a,b)  ((MUL16(a, b) + 16384) >> 15)

#define CELT_PVQ_U(n, k) (ff_celt_pvq_u_row[FFMIN(n, k)][FFMAX(n, k)])

#define CELT_PVQ_V(n, k) (CELT_PVQ_U(n, k) + CELT_PVQ_U(n, (k) + 1))

static inline int16_t celt_cos(int16_t x)

{

    x = (MUL16(x, x) + 4096) >> 13;

    x = (32767-x) + ROUND_MUL16(x, (-7651 + ROUND_MUL16(x, (8277 + ROUND_MUL16(-626, x)))));

    return x + 1;

}

static inline int celt_log2tan(int isin, int icos)

{

    int lc, ls;

    lc = opus_ilog(icos);

    ls = opus_ilog(isin);

    icos <<= 15 - lc;

    isin <<= 15 - ls;

    return (ls << 11) - (lc << 11) +

           ROUND_MUL16(isin, ROUND_MUL16(isin, -2597) + 7932) -

           ROUND_MUL16(icos, ROUND_MUL16(icos, -2597) + 7932);

}

static inline int celt_bits2pulses(const uint8_t *cache, int bits)

{

    // TODO: Find the size of cache and make it into an array in the parameters list

    int i, low = 0, high;

    high = cache[0];

    bits--;

    for (i = 0; i < 6; i++) {

        int center = (low + high + 1) >> 1;

        if (cache[center] >= bits)

            high = center;

        else

            low = center;

    }

    return (bits - (low == 0 ? -1 : cache[low]) <= cache[high] - bits) ? low : high;

}

static inline int celt_pulses2bits(const uint8_t *cache, int pulses)

{

    // TODO: Find the size of cache and make it into an array in the parameters list

   return (pulses == 0) ? 0 : cache[pulses] + 1;

}

static inline void celt_normalize_residual(const int * restrict iy, float * restrict X,

                                           int N, float g)

{

    int i;

    for (i = 0; i < N; i++)

        X[i] = g * iy[i];

}

static void celt_exp_rotation_impl(float *X, uint32_t len, uint32_t stride,

                                   float c, float s)

{

    float *Xptr;

    int i;

    Xptr = X;

    for (i = 0; i < len - stride; i++) {

        float x1     = Xptr[0];

        float x2     = Xptr[stride];

        Xptr[stride] = c * x2 + s * x1;

        *Xptr++      = c * x1 - s * x2;

    }

    Xptr = &X[len - 2 * stride - 1];

    for (i = len - 2 * stride - 1; i >= 0; i--) {

        float x1     = Xptr[0];

        float x2     = Xptr[stride];

        Xptr[stride] = c * x2 + s * x1;

        *Xptr--      = c * x1 - s * x2;

    }

}

static inline void celt_exp_rotation(float *X, uint32_t len,

                                     uint32_t stride, uint32_t K,

                                     enum CeltSpread spread, const int encode)

{

    uint32_t stride2 = 0;

    float c, s;

    float gain, theta;

    int i;

    if (2*K >= len || spread == CELT_SPREAD_NONE)

        return;

    gain = (float)len / (len + (20 - 5*spread) * K);

    theta = M_PI * gain * gain / 4;

    c = cosf(theta);

    s = sinf(theta);

    if (len >= stride << 3) {

        stride2 = 1;

        /* This is just a simple (equivalent) way of computing sqrt(len/stride) with rounding.

        It's basically incrementing long as (stride2+0.5)^2 < len/stride. */

        while ((stride2 * stride2 + stride2) * stride + (stride >> 2) < len)

            stride2++;

    }

    len /= stride;

    for (i = 0; i < stride; i++) {

        if (encode) {

            celt_exp_rotation_impl(X + i * len, len, 1, c, -s);

            if (stride2)

                celt_exp_rotation_impl(X + i * len, len, stride2, s, -c);

        } else {

            if (stride2)

                celt_exp_rotation_impl(X + i * len, len, stride2, s, c);

            celt_exp_rotation_impl(X + i * len, len, 1, c, s);

        }

    }

}

static inline uint32_t celt_extract_collapse_mask(const int *iy, uint32_t N, uint32_t B)

{

    int i, j, N0 = N / B;

    uint32_t collapse_mask = 0;

    if (B <= 1)

        return 1;

    for (i = 0; i < B; i++)

        for (j = 0; j < N0; j++)

            collapse_mask |= (!!iy[i*N0+j]) << i;

    return collapse_mask;

}

static inline void celt_stereo_merge(float *X, float *Y, float mid, int N)

{

    int i;

    float xp = 0, side = 0;

    float E[2];

    float mid2;

    float gain[2];

    /* Compute the norm of X+Y and X-Y as |X|^2 + |Y|^2 +/- sum(xy) */

    for (i = 0; i < N; i++) {

        xp   += X[i] * Y[i];

        side += Y[i] * Y[i];

    }

    /* Compensating for the mid normalization */

    xp *= mid;

    mid2 = mid;

    E[0] = mid2 * mid2 + side - 2 * xp;

    E[1] = mid2 * mid2 + side + 2 * xp;

    if (E[0] < 6e-4f || E[1] < 6e-4f) {

        for (i = 0; i < N; i++)

            Y[i] = X[i];

        return;

    }

    gain[0] = 1.0f / sqrtf(E[0]);

    gain[1] = 1.0f / sqrtf(E[1]);

    for (i = 0; i < N; i++) {

        float value[2];

        /* Apply mid scaling (side is already scaled) */

        value[0] = mid * X[i];

        value[1] = Y[i];

        X[i] = gain[0] * (value[0] - value[1]);

        Y[i] = gain[1] * (value[0] + value[1]);

    }

}

static void celt_interleave_hadamard(float *tmp, float *X, int N0,

                                     int stride, int hadamard)

{

    int i, j, N = N0*stride;

    const uint8_t *order = &ff_celt_hadamard_order[hadamard ? stride - 2 : 30];

    for (i = 0; i < stride; i++)

        for (j = 0; j < N0; j++)

            tmp[j*stride+i] = X[order[i]*N0+j];

    memcpy(X, tmp, N*sizeof(float));

}

static void celt_deinterleave_hadamard(float *tmp, float *X, int N0,

                                       int stride, int hadamard)

{

    int i, j, N = N0*stride;

    const uint8_t *order = &ff_celt_hadamard_order[hadamard ? stride - 2 : 30];

    for (i = 0; i < stride; i++)

        for (j = 0; j < N0; j++)

            tmp[order[i]*N0+j] = X[j*stride+i];

    memcpy(X, tmp, N*sizeof(float));

}

static void celt_haar1(float *X, int N0, int stride)

{

    int i, j;

    N0 >>= 1;

    for (i = 0; i < stride; i++) {

        for (j = 0; j < N0; j++) {

            float x0 = X[stride * (2 * j + 0) + i];

            float x1 = X[stride * (2 * j + 1) + i];

            X[stride * (2 * j + 0) + i] = (x0 + x1) * M_SQRT1_2;

            X[stride * (2 * j + 1) + i] = (x0 - x1) * M_SQRT1_2;

        }

    }

}

static inline int celt_compute_qn(int N, int b, int offset, int pulse_cap,

                                  int stereo)

{

    int qn, qb;

    int N2 = 2 * N - 1;

    if (stereo && N == 2)

        N2--;

    /* The upper limit ensures that in a stereo split with itheta==16384, we'll

     * always have enough bits left over to code at least one pulse in the

     * side; otherwise it would collapse, since it doesn't get folded. */

    qb = FFMIN3(b - pulse_cap - (4 << 3), (b + N2 * offset) / N2, 8 << 3);

    qn = (qb < (1 << 3 >> 1)) ? 1 : ((ff_celt_qn_exp2[qb & 0x7] >> (14 - (qb >> 3))) + 1) >> 1 << 1;

    return qn;

}

/* Convert the quantized vector to an index */

static inline uint32_t celt_icwrsi(uint32_t N, uint32_t K, const int *y)

{

    int i, idx = 0, sum = 0;

    for (i = N - 1; i >= 0; i--) {

        const uint32_t i_s = CELT_PVQ_U(N - i, sum + FFABS(y[i]) + 1);

        idx += CELT_PVQ_U(N - i, sum) + (y[i] < 0)*i_s;

        sum += FFABS(y[i]);

    }

    return idx;

}

// this code was adapted from libopus

static inline uint64_t celt_cwrsi(uint32_t N, uint32_t K, uint32_t i, int *y)

{

    uint64_t norm = 0;

    uint32_t q, p;

    int s, val;

    int k0;

    while (N > 2) {

        /*Lots of pulses case:*/

        if (K >= N) {

            const uint32_t *row = ff_celt_pvq_u_row[N];

            /* Are the pulses in this dimension negative? */

            p  = row[K + 1];

            s  = -(i >= p);

            i -= p & s;

            /*Count how many pulses were placed in this dimension.*/

            k0 = K;

            q = row[N];

            if (q > i) {

                K = N;

                do {

                    p = ff_celt_pvq_u_row[--K][N];

                } while (p > i);

            } else

                for (p = row[K]; p > i; p = row[K])

                    K--;

            i    -= p;

            val   = (k0 - K + s) ^ s;

            norm += val * val;

            *y++  = val;

        } else { /*Lots of dimensions case:*/

            /*Are there any pulses in this dimension at all?*/

            p = ff_celt_pvq_u_row[K    ][N];

            q = ff_celt_pvq_u_row[K + 1][N];

            if (p <= i && i < q) {

                i -= p;

                *y++ = 0;

            } else {

                /*Are the pulses in this dimension negative?*/

                s  = -(i >= q);

                i -= q & s;

                /*Count how many pulses were placed in this dimension.*/

                k0 = K;

                do p = ff_celt_pvq_u_row[--K][N];

                while (p > i);

                i    -= p;

                val   = (k0 - K + s) ^ s;

                norm += val * val;

                *y++  = val;

            }

        }

        N--;

    }

    /* N == 2 */

    p  = 2 * K + 1;

    s  = -(i >= p);

    i -= p & s;

    k0 = K;

    K  = (i + 1) / 2;

    if (K)

        i -= 2 * K - 1;

    val   = (k0 - K + s) ^ s;

    norm += val * val;

    *y++  = val;

    /* N==1 */

    s     = -i;

    val   = (K + s) ^ s;

    norm += val * val;

    *y    = val;

    return norm;

}

static inline void celt_encode_pulses(OpusRangeCoder *rc, int *y, uint32_t N, uint32_t K)

{

    ff_opus_rc_enc_uint(rc, celt_icwrsi(N, K, y), CELT_PVQ_V(N, K));

}

static inline float celt_decode_pulses(OpusRangeCoder *rc, int *y, uint32_t N, uint32_t K)

{

    const uint32_t idx = ff_opus_rc_dec_uint(rc, CELT_PVQ_V(N, K));

    return celt_cwrsi(N, K, idx, y);

}

#if CONFIG_OPUS_ENCODER

/*

 * Faster than libopus's search, operates entirely in the signed domain.

 * Slightly worse/better depending on N, K and the input vector.

 */

static float ppp_pvq_search_c(float *X, int *y, int K, int N)

{

    int i, y_norm = 0;

    float res = 0.0f, xy_norm = 0.0f;

    for (i = 0; i < N; i++)

        res += FFABS(X[i]);

    res = K/(res + FLT_EPSILON);

    for (i = 0; i < N; i++) {

        y[i] = lrintf(res*X[i]);

        y_norm  += y[i]*y[i];

        xy_norm += y[i]*X[i];

        K -= FFABS(y[i]);

    }

    while (K) {

        int max_idx = 0, phase = FFSIGN(K);

        float max_num = 0.0f;

        float max_den = 1.0f;

        y_norm += 1.0f;

        for (i = 0; i < N; i++) {

            /* If the sum has been overshot and the best place has 0 pulses allocated

             * to it, attempting to decrease it further will actually increase the

             * sum. Prevent this by disregarding any 0 positions when decrementing. */

            const int ca = 1 ^ ((y[i] == 0) & (phase < 0));

            const int y_new = y_norm  + 2*phase*FFABS(y[i]);

            float xy_new = xy_norm + 1*phase*FFABS(X[i]);

            xy_new = xy_new * xy_new;

            if (ca && (max_den*xy_new) > (y_new*max_num)) {

                max_den = y_new;

                max_num = xy_new;

                max_idx = i;

            }

        }

        K -= phase;

        phase *= FFSIGN(X[max_idx]);

        xy_norm += 1*phase*X[max_idx];

        y_norm  += 2*phase*y[max_idx];

        y[max_idx] += phase;

    }

    return (float)y_norm;

}

#endif

static uint32_t celt_alg_quant(OpusRangeCoder *rc, float *X, uint32_t N, uint32_t K,

                               enum CeltSpread spread, uint32_t blocks, float gain,

                               CeltPVQ *pvq)

{

    int *y = pvq->qcoeff;

    celt_exp_rotation(X, N, blocks, K, spread, 1);

    gain /= sqrtf(pvq->pvq_search(X, y, K, N));

    celt_encode_pulses(rc, y,  N, K);

    celt_normalize_residual(y, X, N, gain);

    celt_exp_rotation(X, N, blocks, K, spread, 0);

    return celt_extract_collapse_mask(y, N, blocks);

}

/** Decode pulse vector and combine the result with the pitch vector to produce

    the final normalised signal in the current band. */

static uint32_t celt_alg_unquant(OpusRangeCoder *rc, float *X, uint32_t N, uint32_t K,

                                 enum CeltSpread spread, uint32_t blocks, float gain,

                                 CeltPVQ *pvq)

{

    int *y = pvq->qcoeff;

    gain /= sqrtf(celt_decode_pulses(rc, y, N, K));

    celt_normalize_residual(y, X, N, gain);

    celt_exp_rotation(X, N, blocks, K, spread, 0);

    return celt_extract_collapse_mask(y, N, blocks);

}

static int celt_calc_theta(const float *X, const float *Y, int coupling, int N)

{

    int i;

    float e[2] = { 0.0f, 0.0f };

    if (coupling) { /* Coupling case */

        for (i = 0; i < N; i++) {

            e[0] += (X[i] + Y[i])*(X[i] + Y[i]);

            e[1] += (X[i] - Y[i])*(X[i] - Y[i]);

        }

    } else {

        for (i = 0; i < N; i++) {

            e[0] += X[i]*X[i];

            e[1] += Y[i]*Y[i];

        }

    }

    return lrintf(32768.0f*atan2f(sqrtf(e[1]), sqrtf(e[0]))/M_PI);

}

static void celt_stereo_is_decouple(float *X, float *Y, float e_l, float e_r, int N)

{

    int i;

    const float energy_n = 1.0f/(sqrtf(e_l*e_l + e_r*e_r) + FLT_EPSILON);

    e_l *= energy_n;

    e_r *= energy_n;

    for (i = 0; i < N; i++)

        X[i] = e_l*X[i] + e_r*Y[i];

}

static void celt_stereo_ms_decouple(float *X, float *Y, int N)

{

    int i;

    for (i = 0; i < N; i++) {

        const float Xret = X[i];

        X[i] = (X[i] + Y[i])*M_SQRT1_2;

        Y[i] = (Y[i] - Xret)*M_SQRT1_2;

    }

}

static av_always_inline uint32_t quant_band_template(CeltPVQ *pvq, CeltFrame *f,

                                                     OpusRangeCoder *rc,

                                                     const int band, float *X,

                                                     float *Y, int N, int b,

                                                     uint32_t blocks, float *lowband,

                                                     int duration, float *lowband_out,

                                                     int level, float gain,

                                                     float *lowband_scratch,

                                                     int fill, int quant)

{

    int i;

    const uint8_t *cache;

    int stereo = !!Y, split = stereo;

    int imid = 0, iside = 0;

    uint32_t N0 = N;

    int N_B = N / blocks;

    int N_B0 = N_B;

    int B0 = blocks;

    int time_divide = 0;

    int recombine = 0;

    int inv = 0;

    float mid = 0, side = 0;

    int longblocks = (B0 == 1);

    uint32_t cm = 0;

    if (N == 1) {

        float *x = X;

        for (i = 0; i <= stereo; i++) {

            int sign = 0;

            if (f->remaining2 >= 1 << 3) {

                if (quant) {

                    sign = x[0] < 0;

                    ff_opus_rc_put_raw(rc, sign, 1);

                } else {

                    sign = ff_opus_rc_get_raw(rc, 1);

                }

                f->remaining2 -= 1 << 3;

            }

            x[0] = 1.0f - 2.0f*sign;

            x = Y;

        }

        if (lowband_out)

            lowband_out[0] = X[0];

        return 1;

    }

    if (!stereo && level == 0) {

        int tf_change = f->tf_change[band];

        int k;

        if (tf_change > 0)

            recombine = tf_change;

        /* Band recombining to increase frequency resolution */

        if (lowband &&

            (recombine || ((N_B & 1) == 0 && tf_change < 0) || B0 > 1)) {

            for (i = 0; i < N; i++)

                lowband_scratch[i] = lowband[i];

            lowband = lowband_scratch;

        }

        for (k = 0; k < recombine; k++) {

            if (quant || lowband)

                celt_haar1(quant ? X : lowband, N >> k, 1 << k);

            fill = ff_celt_bit_interleave[fill & 0xF] | ff_celt_bit_interleave[fill >> 4] << 2;

        }

        blocks >>= recombine;

        N_B <<= recombine;

        /* Increasing the time resolution */

        while ((N_B & 1) == 0 && tf_change < 0) {

            if (quant || lowband)

                celt_haar1(quant ? X : lowband, N_B, blocks);

            fill |= fill << blocks;

            blocks <<= 1;

            N_B >>= 1;

            time_divide++;

            tf_change++;

        }

        B0 = blocks;

        N_B0 = N_B;

        /* Reorganize the samples in time order instead of frequency order */

        if (B0 > 1 && (quant || lowband))

            celt_deinterleave_hadamard(pvq->hadamard_tmp, quant ? X : lowband,

                                       N_B >> recombine, B0 << recombine,

                                       longblocks);

    }

    /* If we need 1.5 more bit than we can produce, split the band in two. */

    cache = ff_celt_cache_bits +

            ff_celt_cache_index[(duration + 1) * CELT_MAX_BANDS + band];

    if (!stereo && duration >= 0 && b > cache[cache[0]] + 12 && N > 2) {

        N >>= 1;

        Y = X + N;

        split = 1;

        duration -= 1;

        if (blocks == 1)

            fill = (fill & 1) | (fill << 1);

        blocks = (blocks + 1) >> 1;

    }

    if (split) {

        int qn;

        int itheta = quant ? celt_calc_theta(X, Y, stereo, N) : 0;

        int mbits, sbits, delta;

        int qalloc;

        int pulse_cap;

        int offset;

        int orig_fill;

        int tell;

        /* Decide on the resolution to give to the split parameter theta */

        pulse_cap = ff_celt_log_freq_range[band] + duration * 8;

        offset = (pulse_cap >> 1) - (stereo && N == 2 ? CELT_QTHETA_OFFSET_TWOPHASE :

                                                          CELT_QTHETA_OFFSET);

        qn = (stereo && band >= f->intensity_stereo) ? 1 :

             celt_compute_qn(N, b, offset, pulse_cap, stereo);

        tell = opus_rc_tell_frac(rc);

        if (qn != 1) {

            if (quant)

                itheta = (itheta*qn + 8192) >> 14;

            /* Entropy coding of the angle. We use a uniform pdf for the

             * time split, a step for stereo, and a triangular one for the rest. */

            if (quant) {

                if (stereo && N > 2)

                    ff_opus_rc_enc_uint_step(rc, itheta, qn / 2);

                else if (stereo || B0 > 1)

                    ff_opus_rc_enc_uint(rc, itheta, qn + 1);

                else

                    ff_opus_rc_enc_uint_tri(rc, itheta, qn);

                itheta = itheta * 16384 / qn;

                if (stereo) {

                    if (itheta == 0)

                        celt_stereo_is_decouple(X, Y, f->block[0].lin_energy[band],

                                                f->block[1].lin_energy[band], N);

                    else

                        celt_stereo_ms_decouple(X, Y, N);

                }

            } else {

                if (stereo && N > 2)

                    itheta = ff_opus_rc_dec_uint_step(rc, qn / 2);

                else if (stereo || B0 > 1)

                    itheta = ff_opus_rc_dec_uint(rc, qn+1);

                else

                    itheta = ff_opus_rc_dec_uint_tri(rc, qn);

                itheta = itheta * 16384 / qn;

            }

        } else if (stereo) {

            if (quant) {

                inv = f->apply_phase_inv ? itheta > 8192 : 0;

                 if (inv) {

                    for (i = 0; i < N; i++)

                       Y[i] *= -1;

                 }

                 celt_stereo_is_decouple(X, Y, f->block[0].lin_energy[band],

                                         f->block[1].lin_energy[band], N);

                if (b > 2 << 3 && f->remaining2 > 2 << 3) {

                    ff_opus_rc_enc_log(rc, inv, 2);

                } else {

                    inv = 0;

                }

            } else {

                inv = (b > 2 << 3 && f->remaining2 > 2 << 3) ? ff_opus_rc_dec_log(rc, 2) : 0;

                inv = f->apply_phase_inv ? inv : 0;

            }

            itheta = 0;

        }

        qalloc = opus_rc_tell_frac(rc) - tell;

        b -= qalloc;

        orig_fill = fill;

        if (itheta == 0) {

            imid = 32767;

            iside = 0;

            fill = av_zero_extend(fill, blocks);

            delta = -16384;

        } else if (itheta == 16384) {

            imid = 0;

            iside = 32767;

            fill &= ((1 << blocks) - 1) << blocks;

            delta = 16384;

        } else {

            imid = celt_cos(itheta);

            iside = celt_cos(16384-itheta);

            /* This is the mid vs side allocation that minimizes squared error

            in that band. */

            delta = ROUND_MUL16((N - 1) << 7, celt_log2tan(iside, imid));

        }

        mid  = imid  / 32768.0f;

        side = iside / 32768.0f;

        /* This is a special case for N=2 that only works for stereo and takes

        advantage of the fact that mid and side are orthogonal to encode

        the side with just one bit. */

        if (N == 2 && stereo) {

            int c;

            int sign = 0;

            float tmp;

            float *x2, *y2;

            mbits = b;

            /* Only need one bit for the side */

            sbits = (itheta != 0 && itheta != 16384) ? 1 << 3 : 0;

            mbits -= sbits;

            c = (itheta > 8192);

            f->remaining2 -= qalloc+sbits;

            x2 = c ? Y : X;

            y2 = c ? X : Y;

            if (sbits) {

                if (quant) {

                    sign = x2[0]*y2[1] - x2[1]*y2[0] < 0;

                    ff_opus_rc_put_raw(rc, sign, 1);

                } else {

                    sign = ff_opus_rc_get_raw(rc, 1);

                }

            }

            sign = 1 - 2 * sign;

            /* We use orig_fill here because we want to fold the side, but if

            itheta==16384, we'll have cleared the low bits of fill. */

            cm = pvq->quant_band(pvq, f, rc, band, x2, NULL, N, mbits, blocks, lowband, duration,

                                 lowband_out, level, gain, lowband_scratch, orig_fill);

            /* We don't split N=2 bands, so cm is either 1 or 0 (for a fold-collapse),

            and there's no need to worry about mixing with the other channel. */

            y2[0] = -sign * x2[1];

            y2[1] =  sign * x2[0];

            X[0] *= mid;

            X[1] *= mid;

            Y[0] *= side;

            Y[1] *= side;

            tmp = X[0];

            X[0] = tmp - Y[0];

            Y[0] = tmp + Y[0];

            tmp = X[1];

            X[1] = tmp - Y[1];

            Y[1] = tmp + Y[1];

        } else {

            /* "Normal" split code */

            float *next_lowband2     = NULL;

            float *next_lowband_out1 = NULL;

            int next_level = 0;

            int rebalance;

            uint32_t cmt;

            /* Give more bits to low-energy MDCTs than they would

             * otherwise deserve */

            if (B0 > 1 && !stereo && (itheta & 0x3fff)) {

                if (itheta > 8192)

                    /* Rough approximation for pre-echo masking */

                    delta -= delta >> (4 - duration);

                else

                    /* Corresponds to a forward-masking slope of

                     * 1.5 dB per 10 ms */

                    delta = FFMIN(0, delta + (N << 3 >> (5 - duration)));

            }

            mbits = av_clip((b - delta) / 2, 0, b);

            sbits = b - mbits;

            f->remaining2 -= qalloc;

            if (lowband && !stereo)

                next_lowband2 = lowband + N; /* >32-bit split case */

            /* Only stereo needs to pass on lowband_out.

             * Otherwise, it's handled at the end */

            if (stereo)

                next_lowband_out1 = lowband_out;

            else

                next_level = level + 1;

            rebalance = f->remaining2;

            if (mbits >= sbits) {

                /* In stereo mode, we do not apply a scaling to the mid

                 * because we need the normalized mid for folding later */

                cm = pvq->quant_band(pvq, f, rc, band, X, NULL, N, mbits, blocks,

                                     lowband, duration, next_lowband_out1, next_level,

                                     stereo ? 1.0f : (gain * mid), lowband_scratch, fill);

                rebalance = mbits - (rebalance - f->remaining2);

                if (rebalance > 3 << 3 && itheta != 0)

                    sbits += rebalance - (3 << 3);

                /* For a stereo split, the high bits of fill are always zero,

                 * so no folding will be done to the side. */

                cmt = pvq->quant_band(pvq, f, rc, band, Y, NULL, N, sbits, blocks,

                                      next_lowband2, duration, NULL, next_level,

                                      gain * side, NULL, fill >> blocks);

                cm |= cmt << ((B0 >> 1) & (stereo - 1));

            } else {

                /* For a stereo split, the high bits of fill are always zero,

                 * so no folding will be done to the side. */

                cm = pvq->quant_band(pvq, f, rc, band, Y, NULL, N, sbits, blocks,

                                     next_lowband2, duration, NULL, next_level,

                                     gain * side, NULL, fill >> blocks);

                cm <<= ((B0 >> 1) & (stereo - 1));

                rebalance = sbits - (rebalance - f->remaining2);

                if (rebalance > 3 << 3 && itheta != 16384)

                    mbits += rebalance - (3 << 3);

                /* In stereo mode, we do not apply a scaling to the mid because

                 * we need the normalized mid for folding later */

                cm |= pvq->quant_band(pvq, f, rc, band, X, NULL, N, mbits, blocks,

                                      lowband, duration, next_lowband_out1, next_level,

                                      stereo ? 1.0f : (gain * mid), lowband_scratch, fill);

            }

        }

    } else {

        /* This is the basic no-split case */

        uint32_t q         = celt_bits2pulses(cache, b);

        uint32_t curr_bits = celt_pulses2bits(cache, q);

        f->remaining2 -= curr_bits;

        /* Ensures we can never bust the budget */

        while (f->remaining2 < 0 && q > 0) {

            f->remaining2 += curr_bits;

            curr_bits      = celt_pulses2bits(cache, --q);

            f->remaining2 -= curr_bits;

        }

        if (q != 0) {

            /* Finally do the actual (de)quantization */

            if (quant) {

                cm = celt_alg_quant(rc, X, N, (q < 8) ? q : (8 + (q & 7)) << ((q >> 3) - 1),

                                    f->spread, blocks, gain, pvq);

            } else {

                cm = celt_alg_unquant(rc, X, N, (q < 8) ? q : (8 + (q & 7)) << ((q >> 3) - 1),

                                      f->spread, blocks, gain, pvq);

            }

        } else {

            /* If there's no pulse, fill the band anyway */

            uint32_t cm_mask = (1 << blocks) - 1;

            fill &= cm_mask;

            if (fill) {

                if (!lowband) {

                    /* Noise */

                    for (i = 0; i < N; i++)

                        X[i] = (((int32_t)celt_rng(f)) >> 20);

                    cm = cm_mask;

                } else {

                    /* Folded spectrum */

                    for (i = 0; i < N; i++) {

                        /* About 48 dB below the "normal" folding level */

                        X[i] = lowband[i] + (((celt_rng(f)) & 0x8000) ? 1.0f / 256 : -1.0f / 256);

                    }

                    cm = fill;

                }

                celt_renormalize_vector(X, N, gain);

            } else {

                memset(X, 0, N*sizeof(float));

            }

        }

    }

    /* This code is used by the decoder and by the resynthesis-enabled encoder */

    if (stereo) {

        if (N > 2)

            celt_stereo_merge(X, Y, mid, N);

        if (inv) {

            for (i = 0; i < N; i++)

                Y[i] *= -1;

        }

    } else if (level == 0) {