iSAC: Move global trig tables into the codec instance

webrtc/modules/audio_coding/codecs/isac/main/source/structs.h

Index: webrtc/modules/audio_coding/codecs/isac/main/source/structs.h
diff --git a/webrtc/modules/audio_coding/codecs/isac/main/source/structs.h b/webrtc/modules/audio_coding/codecs/isac/main/source/structs.h
index eb85cf34da85390e981124a82e5789ce3c524f9d..c4062d753d0a79fba67baffe161a1f228b70a132 100644
--- a/webrtc/modules/audio_coding/codecs/isac/main/source/structs.h
+++ b/webrtc/modules/audio_coding/codecs/isac/main/source/structs.h
@@ -428,6 +428,16 @@ typedef struct {
   uint8_t  stream[3];
 } transcode_obj;
 
+typedef struct {
+  // TODO(kwiberg): The size of these tables could be reduced by storing floats
+  // instead of doubles, and by making use of the identity cos(x) =
+  // sin(x+pi/2). They could also be made global constants that we fill in at
+  // compile time.
+  double costab1[FRAMESAMPLES_HALF];
+  double sintab1[FRAMESAMPLES_HALF];
+  double costab2[FRAMESAMPLES_QUARTER];
+  double sintab2[FRAMESAMPLES_QUARTER];
+} TransformTables;
 
 typedef struct {
   // lower-band codec instance
@@ -477,6 +487,9 @@ typedef struct {
   uint16_t in_sample_rate_hz;
   /* State for the input-resampler. It is only used for 48 kHz input signals. */
   int16_t state_in_resampler[SIZE_RESAMPLER_STATE];
+
+  // Trig tables for WebRtcIsac_Time2Spec and WebRtcIsac_Spec2time.
+  TransformTables transform_tables;
 } ISACMainStruct;
 
 #endif /* WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_MAIN_SOURCE_STRUCTS_H_ */