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fixed-point: half-way converting mix_pitch_and_residual() -- just check-pointing

--- a/libcelt/vq.c

+++ b/libcelt/vq.c

@@ -62,17 +62,20 @@

 /** Takes the pitch vector and the decoded residual vector (non-compressed), 

    applies the compression in the pitch direction, computes the gain that will

    give ||p+g*y||=1 and mixes the residual with the pitch. */

-static void mix_pitch_and_residual(int *iy, celt_norm_t *X, int N, celt_norm_t *P, celt_word16_t alpha)

+static void mix_pitch_and_residual(int *iy, celt_norm_t *X, int N, int K, celt_norm_t *P, celt_word16_t alpha)

 {

    int i;

    float Rpp=0, Ryp=0, Ryy=0;

+   celt_word32_t Ryp2;

    float g;

-   VARDECL(float *y);

+   VARDECL(celt_norm_t *y);

    VARDECL(float *x);

    VARDECL(float *p);

    float _alpha = Q15_ONE_1*alpha;

-

-   ALLOC(y, N, float);

+#ifdef FIXED_POINT

+   int yshift = 15-EC_ILOG(K);

+#endif

+   ALLOC(y, N, celt_norm_t);

    ALLOC(x, N, float);

    ALLOC(p, N, float);

@@ -84,11 +87,15 @@

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

       Rpp += p[i]*p[i];

+   Ryp2 = 0;

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

-      Ryp += iy[i]*p[i];

+      Ryp2 += MULT16_16(SHL16(iy[i],yshift),P[i]);

+   /* Remove part of the pitch component to compute the real residual from

+      the encoded (int) one */

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

-      y[i] = iy[i] - _alpha*Ryp*p[i];

+      y[i] = SUB16(SHL16(iy[i],yshift),

+                   MULT16_16_Q15(alpha,MULT16_16_Q14(EXTRACT16(SHR32(Ryp2,14)),P[i])));

    /* Recompute after the projection (I think it's right) */

    Ryp = 0;

@@ -341,7 +348,7 @@

    /* Recompute the gain in one pass to reduce the encoder-decoder mismatch

       due to the recursive computation used in quantisation.

       Not quite sure whether we need that or not */

-   mix_pitch_and_residual(iy[0], X, N, P, alpha);

+   mix_pitch_and_residual(iy[0], X, N, K, P, alpha);

 }

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

@@ -351,7 +358,7 @@

    VARDECL(int *iy);

    ALLOC(iy, N, int);

    decode_pulses(iy, N, K, dec);

-   mix_pitch_and_residual(iy, X, N, P, alpha);

+   mix_pitch_and_residual(iy, X, N, K, P, alpha);

 }