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, 11 insertions, 817 deletions

diff --git a/libavcodec/opus_celt.c b/libavcodec/opus_celt.c
index a0f018e664..71ef8965e2 100644
--- a/libavcodec/opus_celt.c
+++ b/libavcodec/opus_celt.c
@@ -24,109 +24,9 @@
  * Opus CELT decoder
  */
 
-#include <stdint.h>
-
-#include "libavutil/float_dsp.h"
-#include "libavutil/libm.h"
-
-#include "mdct15.h"
-#include "opus.h"
+#include "opus_celt.h"
 #include "opustab.h"
-
-enum CeltSpread {
-    CELT_SPREAD_NONE,
-    CELT_SPREAD_LIGHT,
-    CELT_SPREAD_NORMAL,
-    CELT_SPREAD_AGGRESSIVE
-};
-
-typedef struct CeltFrame {
-    float energy[CELT_MAX_BANDS];
-    float prev_energy[2][CELT_MAX_BANDS];
-
-    uint8_t collapse_masks[CELT_MAX_BANDS];
-
-    /* buffer for mdct output + postfilter */
-    DECLARE_ALIGNED(32, float, buf)[2048];
-
-    /* postfilter parameters */
-    int pf_period_new;
-    float pf_gains_new[3];
-    int pf_period;
-    float pf_gains[3];
-    int pf_period_old;
-    float pf_gains_old[3];
-
-    float deemph_coeff;
-} CeltFrame;
-
-struct CeltContext {
-    // constant values that do not change during context lifetime
-    AVCodecContext    *avctx;
-    MDCT15Context     *imdct[4];
-    AVFloatDSPContext  *dsp;
-    int output_channels;
-
-    // values that have inter-frame effect and must be reset on flush
-    CeltFrame frame[2];
-    uint32_t seed;
-    int flushed;
-
-    // values that only affect a single frame
-    int coded_channels;
-    int framebits;
-    int duration;
-
-    /* number of iMDCT blocks in the frame */
-    int blocks;
-    /* size of each block */
-    int blocksize;
-
-    int startband;
-    int endband;
-    int codedbands;
-
-    int anticollapse_bit;
-
-    int intensitystereo;
-    int dualstereo;
-    enum CeltSpread spread;
-
-    int remaining;
-    int remaining2;
-    int fine_bits    [CELT_MAX_BANDS];
-    int fine_priority[CELT_MAX_BANDS];
-    int pulses       [CELT_MAX_BANDS];
-    int tf_change    [CELT_MAX_BANDS];
-
-    DECLARE_ALIGNED(32, float, coeffs)[2][CELT_MAX_FRAME_SIZE];
-    DECLARE_ALIGNED(32, float, scratch)[22 * 8]; // MAX(ff_celt_freq_range) * 1<<CELT_MAX_LOG_BLOCKS
-};
-
-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 uint32_t celt_rng(CeltContext *s)
-{
-    s->seed = 1664525 * s->seed + 1013904223;
-    return s->seed;
-}
+#include "opus_pvq.h"
 
 static void celt_decode_coarse_energy(CeltContext *s, OpusRangeCoder *rc)
 {
@@ -579,711 +479,6 @@ static void celt_decode_allocation(CeltContext *s, OpusRangeCoder *rc)
     }
 }
 
-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, unsigned int len, unsigned int 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, unsigned int len,
-                                     unsigned int stride, unsigned int K,
-                                     enum CeltSpread spread)
-{
-    unsigned int 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 = cos(theta);
-    s = sin(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 unsigned int celt_extract_collapse_mask(const int *iy,
-                                                      unsigned int N,
-                                                      unsigned int B)
-{
-    unsigned int 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_renormalize_vector(float *X, int N, float gain)
-{
-    int i;
-    float g = 1e-15f;
-    for (i = 0; i < N; i++)
-        g += X[i] * X[i];
-    g = gain / sqrtf(g);
-
-    for (i = 0; i < N; i++)
-        X[i] *= g;
-}
-
-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(unsigned int N, unsigned int K, unsigned int 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, unsigned int N, unsigned int K)
-{
-    unsigned int idx;
-#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))
-    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 inline unsigned int celt_alg_unquant(OpusRangeCoder *rc, float *X,
-                                            unsigned int N, unsigned int K,
-                                            enum CeltSpread spread,
-                                            unsigned int 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);
-}
-
-static unsigned int celt_decode_band(CeltContext *s, OpusRangeCoder *rc,
-                                     const int band, float *X, float *Y,
-                                     int N, int b, unsigned int 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;
-    unsigned int 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);
-    unsigned int 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 = 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 = 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 |= 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 = 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 |= 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 */
-        unsigned int q         = celt_bits2pulses(cache, b);
-        unsigned int 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;
-            unsigned int 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;
-}
-
 static void celt_denormalize(CeltContext *s, CeltFrame *frame, float *data)
 {
     int i, j;
@@ -1562,18 +757,17 @@ static void celt_decode_bands(CeltContext *s, OpusRangeCoder *rc)
         }
 
         if (s->dualstereo) {
-            cm[0] = celt_decode_band(s, rc, i, X, NULL, band_size, b / 2, s->blocks,
-                                     effective_lowband != -1 ? norm + (effective_lowband << s->duration) : NULL, s->duration,
-            norm + band_offset, 0, 1.0f, lowband_scratch, cm[0]);
+            cm[0] = ff_celt_decode_band(s, rc, i, X, NULL, band_size, b / 2, s->blocks,
+                                        effective_lowband != -1 ? norm + (effective_lowband << s->duration) : NULL, s->duration,
+                                        norm + band_offset, 0, 1.0f, lowband_scratch, cm[0]);
 
-            cm[1] = celt_decode_band(s, rc, i, Y, NULL, band_size, b/2, s->blocks,
-                                     effective_lowband != -1 ? norm2 + (effective_lowband << s->duration) : NULL, s->duration,
-            norm2 + band_offset, 0, 1.0f, lowband_scratch, cm[1]);
+            cm[1] = ff_celt_decode_band(s, rc, i, Y, NULL, band_size, b/2, s->blocks,
+                                        effective_lowband != -1 ? norm2 + (effective_lowband << s->duration) : NULL, s->duration,
+                                        norm2 + band_offset, 0, 1.0f, lowband_scratch, cm[1]);
         } else {
-            cm[0] = celt_decode_band(s, rc, i, X, Y, band_size, b, s->blocks,
-            effective_lowband != -1 ? norm + (effective_lowband << s->duration) : NULL, s->duration,
-            norm + band_offset, 0, 1.0f, lowband_scratch, cm[0]|cm[1]);
-
+            cm[0] = ff_celt_decode_band(s, rc, i, X, Y, band_size, b, s->blocks,
+                                        effective_lowband != -1 ? norm + (effective_lowband << s->duration) : NULL, s->duration,
+                                        norm + band_offset, 0, 1.0f, lowband_scratch, cm[0]|cm[1]);
             cm[1] = cm[0];
         }