atrac3: Generalize gain compensation code

Move it to the ATRAC common code, so it can be reused
in the umpcoming ATRAC3+ decoder.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 45 insertions, 0 deletions

diff --git a/libavcodec/atrac.h b/libavcodec/atrac.h
index fec66bd2a7..e47d4ca18d 100644
--- a/libavcodec/atrac.h
+++ b/libavcodec/atrac.h
@@ -29,6 +29,26 @@
 #ifndef AVCODEC_ATRAC_H
 #define AVCODEC_ATRAC_H
 
+/**
+ *  Gain control parameters for one subband.
+ */
+typedef struct AtracGainInfo {
+    int   num_points; ///< number of gain control points
+    int   levcode[7]; ///< level at corresponding control point
+    int   loccode[7]; ///< location of gain control points
+} AtracGainInfo;
+
+/**
+ *  Gain compensation context structure.
+ */
+typedef struct AtracGCContext {
+    float   gain_tab1[16]; ///< gain compensation level table
+    float   gain_tab2[31]; ///< gain compensation interpolation table
+    int     id2exp_offset; ///< offset for converting level index into level exponent
+    int     loc_scale;     ///< scale of location code = 2^loc_scale samples
+    int     loc_size;      ///< size of location code in samples
+} AtracGCContext;
+
 extern float ff_atrac_sf_table[64];
 
 /**
@@ -37,6 +57,31 @@ extern float ff_atrac_sf_table[64];
 void ff_atrac_generate_tables(void);
 
 /**
+ *  Initialize gain compensation context.
+ *
+ * @param gctx            pointer to gain compensation context to initialize
+ * @param id2exp_offset   offset for converting level index into level exponent
+ * @param loc_scale       location size factor
+ */
+void ff_atrac_init_gain_compensation(AtracGCContext *gctx, int id2exp_offset,
+                                     int loc_scale);
+
+/**
+ * Apply gain compensation and perform the MDCT overlapping part.
+ *
+ * @param gctx         pointer to gain compensation context
+ * @param in           input buffer
+ * @param prev         previous buffer to perform overlap against
+ * @param gc_now       gain control information for current frame
+ * @param gc_next      gain control information for next frame
+ * @param num_samples  number of samples to process
+ * @param out          output data goes here
+ */
+void ff_atrac_gain_compensation(AtracGCContext *gctx, float *in, float *prev,
+                                AtracGainInfo *gc_now, AtracGainInfo *gc_next,
+                                int num_samples, float *out);
+
+/**
  * Quadrature mirror synthesis filter.
  *
  * @param inlo      lower part of spectrum