/**
* Upsample by a factor 4. Note: very low quality, only use with output sampling rates above 96
* kHz.
*
* @param S State vector [ 2 ].
* @param S_offset offset of valid data.
* @param out Output signal [ 4 * len ].
* @param out_offset offset of valid data.
* @param in Input signal [ len ].
* @param in_offset offset of valid data.
* @param len Number of INPUT samples.
*/
static void SKP_Silk_resampler_private_up4(
int[] S, /* I/O: State vector [ 2 ] */
int S_offset,
short[] out, /* O: Output signal [ 4 * len ] */
int out_offset,
short[] in, /* I: Input signal [ len ] */
int in_offset,
int len /* I: Number of INPUT samples */) {
int k;
int in32, out32, Y, X;
int out16;
assert (ResamplerRom.SKP_Silk_resampler_up2_lq_0 > 0);
assert (ResamplerRom.SKP_Silk_resampler_up2_lq_1 < 0);
/* Internal variables and state are in Q10 format */
for (k = 0; k < len; k++) {
/* Convert to Q10 */
in32 = in[in_offset + k] << 10;
/* All-pass section for even output sample */
Y = in32 - S[S_offset + 0];
X = SKP_SMULWB(Y, ResamplerRom.SKP_Silk_resampler_up2_lq_0);
out32 = S[S_offset + 0] + X;
S[S_offset + 0] = in32 + X;
/* Convert back to int16 and store to output */
out16 = (short) SigProcFIX.SKP_SAT16(SigProcFIX.SKP_RSHIFT_ROUND(out32, 10));
out[out_offset + 4 * k] = (short) out16;
out[out_offset + 4 * k + 1] = (short) out16;
/* All-pass section for odd output sample */
Y = in32 - S[S_offset + 1];
X = SKP_SMLAWB(Y, Y, ResamplerRom.SKP_Silk_resampler_up2_lq_1);
out32 = S[S_offset + 1] + X;
S[S_offset + 1] = in32 + X;
/* Convert back to int16 and store to output */
out16 = (short) SigProcFIX.SKP_SAT16(SigProcFIX.SKP_RSHIFT_ROUND(out32, 10));
out[out_offset + 4 * k + 2] = (short) out16;
out[out_offset + 4 * k + 3] = (short) out16;
}
}
/**
* Downsample by a factor 4. Note: very low quality, only use with input sampling rates above 96
* kHz.
*
* @param S State vector [ 2 ].
* @param S_offset offset of valid data.
* @param out Output signal [ floor(len/2) ].
* @param out_offset offset of valid data.
* @param in Input signal [ len ].
* @param in_offset offset of valid data.
* @param inLen Number of input samples.
*/
static void SKP_Silk_resampler_private_down4(
int[] S, /* I/O: State vector [ 2 ] */
int S_offset,
short[] out, /* O: Output signal [ floor(len/2) ] */
int out_offset,
short[] in, /* I: Input signal [ len ] */
int in_offset,
int inLen /* I: Number of input samples */) {
int k, len4 = inLen >> 2;
int in32, out32, Y, X;
assert (ResamplerRom.SKP_Silk_resampler_down2_0 > 0);
assert (ResamplerRom.SKP_Silk_resampler_down2_1 < 0);
/* Internal variables and state are in Q10 format */
for (k = 0; k < len4; k++) {
/* Add two input samples and convert to Q10 */
in32 = (in[in_offset + 4 * k] + in[in_offset + 4 * k + 1]) << 9;
/* All-pass section for even input sample */
Y = in32 - S[S_offset];
X = SKP_SMLAWB(Y, Y, ResamplerRom.SKP_Silk_resampler_down2_1);
out32 = S[S_offset] + X;
S[S_offset] = in32 + X;
/* Add two input samples and convert to Q10 */
in32 = (in[in_offset + 4 * k + 2] + in[in_offset + 4 * k + 3]) << 9;
/* All-pass section for odd input sample */
Y = in32 - S[S_offset + 1];
X = SKP_SMULWB(Y, ResamplerRom.SKP_Silk_resampler_down2_0);
out32 = out32 + S[S_offset + 1];
out32 = out32 + X;
S[S_offset + 1] = in32 + X;
/* Add, convert back to int16 and store to output */
out[out_offset + k] = (short) SigProcFIX.SKP_SAT16(SigProcFIX.SKP_RSHIFT_ROUND(out32, 11));
}
}