-/**
+/*
* LPC utility code
* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
*
- * This file is part of FFmpeg.
+ * This file is part of Libav.
*
- * FFmpeg is free software; you can redistribute it and/or
+ * Libav 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,
+ * Libav 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
+ * License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#define MIN_LPC_ORDER 1
#define MAX_LPC_ORDER 32
+/**
+ * LPC analysis type
+ */
+enum FFLPCType {
+ FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type
+ FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients
+ FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients
+ FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion
+ FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization
+ FF_LPC_TYPE_NB , ///< Not part of ABI
+};
+
+typedef struct LPCContext {
+ int blocksize;
+ int max_order;
+ enum FFLPCType lpc_type;
+ double *windowed_buffer;
+ double *windowed_samples;
+
+ /**
+ * Apply a Welch window to an array of input samples.
+ * The output samples have the same scale as the input, but are in double
+ * sample format.
+ * @param data input samples
+ * @param len number of input samples
+ * @param w_data output samples
+ */
+ void (*lpc_apply_welch_window)(const int32_t *data, int len,
+ double *w_data);
+ /**
+ * Perform autocorrelation on input samples with delay of 0 to lag.
+ * @param data input samples.
+ * constraints: no alignment needed, but must have have at
+ * least lag*sizeof(double) valid bytes preceding it, and
+ * size must be at least (len+1)*sizeof(double) if data is
+ * 16-byte aligned or (len+2)*sizeof(double) if data is
+ * unaligned.
+ * @param len number of input samples to process
+ * @param lag maximum delay to calculate
+ * @param autoc output autocorrelation coefficients.
+ * constraints: array size must be at least lag+1.
+ */
+ void (*lpc_compute_autocorr)(const double *data, int len, int lag,
+ double *autoc);
+} LPCContext;
+
/**
* Calculate LPC coefficients for multiple orders
*/
-int ff_lpc_calc_coefs(DSPContext *s,
+int ff_lpc_calc_coefs(LPCContext *s,
const int32_t *samples, int blocksize, int min_order,
int max_order, int precision,
- int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
+ int32_t coefs[][MAX_LPC_ORDER], int *shift,
+ enum FFLPCType lpc_type, int lpc_passes,
int omethod, int max_shift, int zero_shift);
+int ff_lpc_calc_ref_coefs(LPCContext *s,
+ const int32_t *samples, int order, double *ref);
+
+/**
+ * Initialize LPCContext.
+ */
+int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
+ enum FFLPCType lpc_type);
+void ff_lpc_init_x86(LPCContext *s);
+
+/**
+ * Uninitialize LPCContext.
+ */
+void ff_lpc_end(LPCContext *s);
+
+#ifdef LPC_USE_DOUBLE
+#define LPC_TYPE double
+#else
+#define LPC_TYPE float
+#endif
+
+/**
+ * Schur recursion.
+ * Produces reflection coefficients from autocorrelation data.
+ */
+static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
+ LPC_TYPE *ref, LPC_TYPE *error)
+{
+ int i, j;
+ LPC_TYPE err;
+ LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
+
+ for (i = 0; i < max_order; i++)
+ gen0[i] = gen1[i] = autoc[i + 1];
+
+ err = autoc[0];
+ ref[0] = -gen1[0] / err;
+ err += gen1[0] * ref[0];
+ if (error)
+ error[0] = err;
+ for (i = 1; i < max_order; i++) {
+ for (j = 0; j < max_order - i; j++) {
+ gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
+ gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
+ }
+ ref[i] = -gen1[0] / err;
+ err += gen1[0] * ref[i];
+ if (error)
+ error[i] = err;
+ }
+}
+
+/**
+ * Levinson-Durbin recursion.
+ * Produce LPC coefficients from autocorrelation data.
+ */
+static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
+ LPC_TYPE *lpc, int lpc_stride, int fail,
+ int normalize)
+{
+ int i, j;
+ LPC_TYPE err;
+ LPC_TYPE *lpc_last = lpc;
+
+ if (normalize)
+ err = *autoc++;
+
+ if (fail && (autoc[max_order - 1] == 0 || err <= 0))
+ return -1;
+
+ for(i=0; i<max_order; i++) {
+ LPC_TYPE r = -autoc[i];
+
+ if (normalize) {
+ for(j=0; j<i; j++)
+ r -= lpc_last[j] * autoc[i-j-1];
+
+ r /= err;
+ err *= 1.0 - (r * r);
+ }
+
+ lpc[i] = r;
+
+ for(j=0; j < (i+1)>>1; j++) {
+ LPC_TYPE f = lpc_last[ j];
+ LPC_TYPE b = lpc_last[i-1-j];
+ lpc[ j] = f + r * b;
+ lpc[i-1-j] = b + r * f;
+ }
+
+ if (fail && err < 0)
+ return -1;
+
+ lpc_last = lpc;
+ lpc += lpc_stride;
+ }
+
+ return 0;
+}
+
#endif /* AVCODEC_LPC_H */
projects / ffmpeg / blobdiff