+#define COEFF_BITS 12
+
+#define BLOCK_SIZE 18
+#define BLOCK_SAMPLES 32
+
+/**
+ * Calculate LPC coefficients based on cutoff frequency and sample rate.
+ *
+ * @param cutoff cutoff frequency
+ * @param sample_rate sample rate
+ * @param bits number of bits used to quantize coefficients
+ * @param[out] coeff 2 quantized LPC coefficients
+ */
+void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff);
+
+/**
+ * Decode ADX stream header.
+ * Sets avctx->channels and avctx->sample_rate.
+ *
+ * @param avctx codec context
+ * @param buf header data
+ * @param bufsize data size, should be at least 24 bytes
+ * @param[out] header_size size of ADX header
+ * @param[out] coeff 2 LPC coefficients, can be NULL
+ * @return data offset or negative error code if header is invalid
+ */
+int avpriv_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,
+ int bufsize, int *header_size, int *coeff);