libtwamr encoder: always emit frame->mode = mode; In the original implementation of amr_encode_frame(), the 'mode' member of the output struct was set to 0xFF if the output frame type is TX_NO_DATA. This design was made to mimic the mode field (16-bit word) being set to 0xFFFF (or -1) in 3GPP test sequence format - but nothing actually depends on this struct member being set in any way, and amr_frame_to_tseq() generates the needed 0xFFFF on its own, based on frame->type being equal to TX_NO_DATA. It is simpler and more efficient to always set frame->mode to the actual encoding mode in amr_encode_frame(), and this new behavior has already been documented in doc/AMR-library-API description in anticipation of the present change.

/*
 * The definitions contained in this header file originally lived in
 * dtx.c; they are being factored out into a new header file as part of
 * splitting of dtx.c code into common, encoder-only and decoder-only
 * parts.
 */

/* Inverse values of DTX hangover period and DTX hangover period + 1 */

#define INV_DTX_HANGOVER (0x7fff / DTX_HANGOVER)
#define INV_DTX_HANGOVER_P1 (0x7fff / (DTX_HANGOVER+1))

#define NB_PULSE 10 /* Number of pulses in fixed codebook excitation */

/* Constant DTX_ELAPSED_THRESHOLD is used as threshold for allowing
   SID frame updating without hangover period in case when elapsed
   time measured from previous SID update is below 24 */

#define DTX_ELAPSED_THRESHOLD (24 + DTX_HANGOVER - 1)