opus_celt: move quantization and band decoding to opus_pvq.c

A huge amount can be reused by the encoder, as the only thing
which needs to be done would be to add a 10 line celt_icwrsi,
a wrapper around it (celt_alg_quant) and templating the
ff_celt_decode_band to replace entropy decoding functions
with entropy encoding.

There is no performance loss but in fact a performance gain of
around 6% which is caused by the compiler being able to optimize
the decoding more efficiently.

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

1 files changed, 729 insertions, 0 deletions

diff --git a/libavcodec/opus_pvq.c b/libavcodec/opus_pvq.c
new file mode 100644
index 0000000000..b4e23c86b8
--- /dev/null
+++ b/libavcodec/opus_pvq.c
@@ -0,0 +1,729 @@
+/*
+ * Copyright (c) 2012 Andrew D'Addesio
+ * Copyright (c) 2013-2014 Mozilla Corporation
+ * Copyright (c) 2016 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 "opustab.h"
+#include "opus_pvq.h"
+
+#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 1+x;
+}
+
+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 * av_restrict iy, float * av_restrict X,
+                                           int N, float g)
+{
+    int i;
+    for (i = 0; i < N; i++)
+        X[i] = g * iy[i];
+}
+
+static void celt_exp_rotation1(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, x2;
+        x1           = Xptr[0];
+        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, x2;
+        x1           = Xptr[0];
+        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)
+{
+    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++;
+    }
+
+    /*NOTE: As a minor optimization, we could be passing around log2(B), not B, for both this and for
+    extract_collapse_mask().*/
+    len /= stride;
+    for (i = 0; i < stride; i++) {
+        if (stride2)
+            celt_exp_rotation1(X + i * len, len, stride2, s, c);
+        celt_exp_rotation1(X + i * len, len, 1, c, s);
+    }
+}
+
+static inline uint32_t celt_extract_collapse_mask(const int *iy, uint32_t N, uint32_t B)
+{
+    uint32_t collapse_mask;
+    int N0;
+    int i, j;
+
+    if (B <= 1)
+        return 1;
+
+    /*NOTE: As a minor optimization, we could be passing around log2(B), not B, for both this and for
+    exp_rotation().*/
+    N0 = N/B;
+    collapse_mask = 0;
+    for (i = 0; i < B; i++)
+        for (j = 0; j < N0; j++)
+            collapse_mask |= (iy[i*N0+j]!=0)<<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 t, 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;
+    }
+
+    t = E[0];
+    gain[0] = 1.0f / sqrtf(t);
+    t = E[1];
+    gain[1] = 1.0f / sqrtf(t);
+
+    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;
+    int N = N0*stride;
+
+    if (hadamard) {
+        const uint8_t *ordery = ff_celt_hadamard_ordery + stride - 2;
+        for (i = 0; i < stride; i++)
+            for (j = 0; j < N0; j++)
+                tmp[j*stride+i] = X[ordery[i]*N0+j];
+    } else {
+        for (i = 0; i < stride; i++)
+            for (j = 0; j < N0; j++)
+                tmp[j*stride+i] = X[i*N0+j];
+    }
+
+    for (i = 0; i < N; i++)
+        X[i] = tmp[i];
+}
+
+static void celt_deinterleave_hadamard(float *tmp, float *X, int N0,
+                                       int stride, int hadamard)
+{
+    int i, j;
+    int N = N0*stride;
+
+    if (hadamard) {
+        const uint8_t *ordery = ff_celt_hadamard_ordery + stride - 2;
+        for (i = 0; i < stride; i++)
+            for (j = 0; j < N0; j++)
+                tmp[ordery[i]*N0+j] = X[j*stride+i];
+    } else {
+        for (i = 0; i < stride; i++)
+            for (j = 0; j < N0; j++)
+                tmp[i*N0+j] = X[j*stride+i];
+    }
+
+    for (i = 0; i < N; i++)
+        X[i] = tmp[i];
+}
+
+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 dualstereo)
+{
+    int qn, qb;
+    int N2 = 2 * N - 1;
+    if (dualstereo && 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;
+}
+
+// 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 p;
+    int s, val;
+    int k0;
+
+    while (N > 2) {
+        uint32_t q;
+
+        /*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 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);
+}
+
+/** 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)
+{
+    int y[176];
+
+    gain /= sqrtf(celt_decode_pulses(rc, y, N, K));
+    celt_normalize_residual(y, X, N, gain);
+    celt_exp_rotation(X, N, blocks, K, spread);
+    return celt_extract_collapse_mask(y, N, blocks);
+}
+
+uint32_t ff_celt_decode_band(CeltContext *s, 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)
+{
+    const uint8_t *cache;
+    int dualstereo, split;
+    int imid = 0, iside = 0;
+    uint32_t N0 = N;
+    int N_B;
+    int N_B0;
+    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;
+
+    N_B0 = N_B = N / blocks;
+    split = dualstereo = (Y != NULL);
+
+    if (N == 1) {
+        /* special case for one sample */
+        int i;
+        float *x = X;
+        for (i = 0; i <= dualstereo; i++) {
+            int sign = 0;
+            if (s->remaining2 >= 1<<3) {
+                sign           = ff_opus_rc_get_raw(rc, 1);
+                s->remaining2 -= 1 << 3;
+                b             -= 1 << 3;
+            }
+            x[0] = sign ? -1.0f : 1.0f;
+            x = Y;
+        }
+        if (lowband_out)
+            lowband_out[0] = X[0];
+        return 1;
+    }
+
+    if (!dualstereo && level == 0) {
+        int tf_change = s->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)) {
+            int j;
+            for (j = 0; j < N; j++)
+                lowband_scratch[j] = lowband[j];
+            lowband = lowband_scratch;
+        }
+
+        for (k = 0; k < recombine; k++) {
+            if (lowband)
+                celt_haar1(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 (lowband)
+                celt_haar1(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 && lowband)
+            celt_deinterleave_hadamard(s->scratch, 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 (!dualstereo && 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 = 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) - (dualstereo && N == 2 ? CELT_QTHETA_OFFSET_TWOPHASE :
+                                                          CELT_QTHETA_OFFSET);
+        qn = (dualstereo && band >= s->intensitystereo) ? 1 :
+             celt_compute_qn(N, b, offset, pulse_cap, dualstereo);
+        tell = opus_rc_tell_frac(rc);
+        if (qn != 1) {
+            /* 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 (dualstereo && N > 2)
+                itheta = ff_opus_rc_dec_uint_step(rc, qn/2);
+            else if (dualstereo || 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;
+            /* NOTE: Renormalising X and Y *may* help fixed-point a bit at very high rate.
+            Let's do that at higher complexity */
+        } else if (dualstereo) {
+            inv = (b > 2 << 3 && s->remaining2 > 2 << 3) ? ff_opus_rc_dec_log(rc, 2) : 0;
+            itheta = 0;
+        }
+        qalloc = opus_rc_tell_frac(rc) - tell;
+        b -= qalloc;
+
+        orig_fill = fill;
+        if (itheta == 0) {
+            imid = 32767;
+            iside = 0;
+            fill = av_mod_uintp2(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 && dualstereo) {
+            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);
+            s->remaining2 -= qalloc+sbits;
+
+            x2 = c ? Y : X;
+            y2 = c ? X : Y;
+            if (sbits)
+                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 = ff_celt_decode_band(s, 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;
+
+            /* Give more bits to low-energy MDCTs than they would
+             * otherwise deserve */
+            if (B0 > 1 && !dualstereo && (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;
+            s->remaining2 -= qalloc;
+
+            if (lowband && !dualstereo)
+                next_lowband2 = lowband + N; /* >32-bit split case */
+
+            /* Only stereo needs to pass on lowband_out.
+             * Otherwise, it's handled at the end */
+            if (dualstereo)
+                next_lowband_out1 = lowband_out;
+            else
+                next_level = level + 1;
+
+            rebalance = s->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 = ff_celt_decode_band(s, rc, band, X, NULL, N, mbits, blocks,
+                                         lowband, duration, next_lowband_out1,
+                                         next_level, dualstereo ? 1.0f : (gain * mid),
+                                         lowband_scratch, fill);
+
+                rebalance = mbits - (rebalance - s->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. */
+                cm |= ff_celt_decode_band(s, rc, band, Y, NULL, N, sbits, blocks,
+                                          next_lowband2, duration, NULL,
+                                          next_level, gain * side, NULL,
+                                          fill >> blocks) << ((B0 >> 1) & (dualstereo - 1));
+            } else {
+                /* For a stereo split, the high bits of fill are always zero,
+                 * so no folding will be done to the side. */
+                cm = ff_celt_decode_band(s, rc, band, Y, NULL, N, sbits, blocks,
+                                         next_lowband2, duration, NULL,
+                                         next_level, gain * side, NULL,
+                                         fill >> blocks) << ((B0 >> 1) & (dualstereo - 1));
+
+                rebalance = sbits - (rebalance - s->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 |= ff_celt_decode_band(s, rc, band, X, NULL, N, mbits, blocks,
+                                          lowband, duration, next_lowband_out1,
+                                          next_level, dualstereo ? 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);
+        s->remaining2 -= curr_bits;
+
+        /* Ensures we can never bust the budget */
+        while (s->remaining2 < 0 && q > 0) {
+            s->remaining2 += curr_bits;
+            curr_bits      = celt_pulses2bits(cache, --q);
+            s->remaining2 -= curr_bits;
+        }
+
+        if (q != 0) {
+            /* Finally do the actual quantization */
+            cm = celt_alg_unquant(rc, X, N, (q < 8) ? q : (8 + (q & 7)) << ((q >> 3) - 1),
+                                  s->spread, blocks, gain);
+        } else {
+            /* If there's no pulse, fill the band anyway */
+            int j;
+            uint32_t cm_mask = (1 << blocks) - 1;
+            fill &= cm_mask;
+            if (!fill) {
+                for (j = 0; j < N; j++)
+                    X[j] = 0.0f;
+            } else {
+                if (!lowband) {
+                    /* Noise */
+                    for (j = 0; j < N; j++)
+                        X[j] = (((int32_t)celt_rng(s)) >> 20);
+                    cm = cm_mask;
+                } else {
+                    /* Folded spectrum */
+                    for (j = 0; j < N; j++) {
+                        /* About 48 dB below the "normal" folding level */
+                        X[j] = lowband[j] + (((celt_rng(s)) & 0x8000) ? 1.0f / 256 : -1.0f / 256);
+                    }
+                    cm = fill;
+                }
+                celt_renormalize_vector(X, N, gain);
+            }
+        }
+    }
+
+    /* This code is used by the decoder and by the resynthesis-enabled encoder */
+    if (dualstereo) {
+        int j;
+        if (N != 2)
+            celt_stereo_merge(X, Y, mid, N);
+        if (inv) {
+            for (j = 0; j < N; j++)
+                Y[j] *= -1;
+        }
+    } else if (level == 0) {
+        int k;
+
+        /* Undo the sample reorganization going from time order to frequency order */
+        if (B0 > 1)
+            celt_interleave_hadamard(s->scratch, X, N_B>>recombine,
+                                     B0<<recombine, longblocks);
+
+        /* Undo time-freq changes that we did earlier */
+        N_B = N_B0;
+        blocks = B0;
+        for (k = 0; k < time_divide; k++) {
+            blocks >>= 1;
+            N_B <<= 1;
+            cm |= cm >> blocks;
+            celt_haar1(X, N_B, blocks);
+        }
+
+        for (k = 0; k < recombine; k++) {
+            cm = ff_celt_bit_deinterleave[cm];
+            celt_haar1(X, N0>>k, 1<<k);
+        }
+        blocks <<= recombine;
+
+        /* Scale output for later folding */
+        if (lowband_out) {
+            int j;
+            float n = sqrtf(N0);
+            for (j = 0; j < N0; j++)
+                lowband_out[j] = n * X[j];
+        }
+        cm = av_mod_uintp2(cm, blocks);
+    }
+    return cm;
+}