+/**
+ * The point during decoding at which channel coupling is applied.
+ */
+enum CouplingPoint {
+ BEFORE_TNS,
+ BETWEEN_TNS_AND_IMDCT,
+ AFTER_IMDCT = 3,
+};
+
+/**
+ * Output configuration status
+ */
+enum OCStatus {
+ OC_NONE, //< Output unconfigured
+ OC_TRIAL_PCE, //< Output configuration under trial specified by an inband PCE
+ OC_TRIAL_FRAME, //< Output configuration under trial specified by a frame header
+ OC_GLOBAL_HDR, //< Output configuration set in a global header but not yet locked
+ OC_LOCKED, //< Output configuration locked in place
+};
+
+/**
+ * Predictor State
+ */
+typedef struct {
+ float cor0;
+ float cor1;
+ float var0;
+ float var1;
+ float r0;
+ float r1;
+} PredictorState;
+
+#define MAX_PREDICTORS 672
+
+#define SCALE_DIV_512 36 ///< scalefactor difference that corresponds to scale difference in 512 times
+#define SCALE_ONE_POS 140 ///< scalefactor index that corresponds to scale=1.0
+#define SCALE_MAX_POS 255 ///< scalefactor index maximum value
+#define SCALE_MAX_DIFF 60 ///< maximum scalefactor difference allowed by standard
+#define SCALE_DIFF_ZERO 60 ///< codebook index corresponding to zero scalefactor indices difference
+
+/**
+ * Individual Channel Stream
+ */
+typedef struct {
+ uint8_t max_sfb; ///< number of scalefactor bands per group
+ enum WindowSequence window_sequence[2];
+ uint8_t use_kb_window[2]; ///< If set, use Kaiser-Bessel window, otherwise use a sinus window.
+ int num_window_groups;
+ uint8_t group_len[8];
+ const uint16_t *swb_offset; ///< table of offsets to the lowest spectral coefficient of a scalefactor band, sfb, for a particular window
+ const uint8_t *swb_sizes; ///< table of scalefactor band sizes for a particular window
+ int num_swb; ///< number of scalefactor window bands
+ int num_windows;
+ int tns_max_bands;
+ int predictor_present;
+ int predictor_initialized;
+ int predictor_reset_group;
+ uint8_t prediction_used[41];
+} IndividualChannelStream;
+
+/**
+ * Temporal Noise Shaping
+ */
+typedef struct {
+ int present;
+ int n_filt[8];
+ int length[8][4];
+ int direction[8][4];
+ int order[8][4];
+ float coef[8][4][TNS_MAX_ORDER];
+} TemporalNoiseShaping;
+
+/**
+ * Dynamic Range Control - decoded from the bitstream but not processed further.
+ */
+typedef struct {
+ int pce_instance_tag; ///< Indicates with which program the DRC info is associated.
+ int dyn_rng_sgn[17]; ///< DRC sign information; 0 - positive, 1 - negative
+ int dyn_rng_ctl[17]; ///< DRC magnitude information
+ int exclude_mask[MAX_CHANNELS]; ///< Channels to be excluded from DRC processing.
+ int band_incr; ///< Number of DRC bands greater than 1 having DRC info.
+ int interpolation_scheme; ///< Indicates the interpolation scheme used in the SBR QMF domain.
+ int band_top[17]; ///< Indicates the top of the i-th DRC band in units of 4 spectral lines.
+ int prog_ref_level; /**< A reference level for the long-term program audio level for all
+ * channels combined.
+ */
+} DynamicRangeControl;
+
+typedef struct {
+ int num_pulse;
+ int start;
+ int pos[4];
+ int amp[4];
+} Pulse;
+
+/**
+ * coupling parameters
+ */
+typedef struct {
+ enum CouplingPoint coupling_point; ///< The point during decoding at which coupling is applied.
+ int num_coupled; ///< number of target elements
+ enum RawDataBlockType type[8]; ///< Type of channel element to be coupled - SCE or CPE.
+ int id_select[8]; ///< element id
+ int ch_select[8]; /**< [0] shared list of gains; [1] list of gains for right channel;
+ * [2] list of gains for left channel; [3] lists of gains for both channels
+ */
+ float gain[16][120];
+} ChannelCoupling;
+
+/**
+ * Single Channel Element - used for both SCE and LFE elements.
+ */
+typedef struct {
+ IndividualChannelStream ics;
+ TemporalNoiseShaping tns;
+ Pulse pulse;
+ enum BandType band_type[128]; ///< band types
+ int band_type_run_end[120]; ///< band type run end points
+ float sf[120]; ///< scalefactors
+ int sf_idx[128]; ///< scalefactor indices (used by encoder)
+ uint8_t zeroes[128]; ///< band is not coded (used by encoder)
+ DECLARE_ALIGNED_16(float, coeffs[1024]); ///< coefficients for IMDCT
+ DECLARE_ALIGNED_16(float, saved[1024]); ///< overlap
+ DECLARE_ALIGNED_16(float, ret[1024]); ///< PCM output
+ PredictorState predictor_state[MAX_PREDICTORS];
+} SingleChannelElement;
+
+/**
+ * channel element - generic struct for SCE/CPE/CCE/LFE
+ */
+typedef struct {
+ // CPE specific
+ int common_window; ///< Set if channels share a common 'IndividualChannelStream' in bitstream.
+ int ms_mode; ///< Signals mid/side stereo flags coding mode (used by encoder)
+ uint8_t ms_mask[128]; ///< Set if mid/side stereo is used for each scalefactor window band
+ // shared
+ SingleChannelElement ch[2];
+ // CCE specific
+ ChannelCoupling coup;
+} ChannelElement;
+