Fix the side frame conditional coding rules.
b24e5746 introduced changes to LastGainIndex which broke
conditional coding for side frames after a mid-only frame (i.e.,
in a 60 ms frame where the side is coded, not coded, then coded
again).
These rules were a mess in general, however, because the side
channel state kept a different nFramesDecoded count from the mid
channel state, and had no way to tell if the prior side frame was
coded.
This patch attempts to rationalize them by moving the conditional
coding decision up to the top level, where all this information is
available.
The first coded side frame after an uncoded side frame now always
uses independent coding.
If such a frame is also not the first side frame in an Opus frame,
then it doesn't include an LTP scaling parameter (because the LTP
state is well-defined).
diff --git a/silk/define.h b/silk/define.h
index f56ca2d..8f9935f 100644
--- a/silk/define.h
+++ b/silk/define.h
@@ -66,6 +66,11 @@
#define TYPE_UNVOICED 1
#define TYPE_VOICED 2
+/* Conditional coding types */
+#define CODE_INDEPENDENTLY 0
+#define CODE_INDEPENDENTLY_NO_LTP_SCALING 1
+#define CODE_CONDITIONALLY 2
+
/* Settings for stereo processing */
#define STEREO_QUANT_TAB_SIZE 16
#define STEREO_QUANT_SUB_STEPS 5