+/**
+ * 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;
+