FS-8344: mod_opus: toggle FEC on the last frame which is to be packed, so that

FEC will be only present on the first SILK frame of the next Opus frame (Opus repacketization).

diff --git a/src/mod/codecs/mod_opus/mod_opus.c b/src/mod/codecs/mod_opus/mod_opus.c
index 9b9ec670e0ea35efe085393b0e08a089d972a9e5..c0e4222211d6a8d087b553d7915ab4a0ff5f4070 100644 (file)
--- a/src/mod/codecs/mod_opus/mod_opus.c
+++ b/src/mod/codecs/mod_opus/mod_opus.c
@@ -874,7 +874,6 @@ static switch_status_t switch_opus_encode_repacketize(switch_codec_t *codec,
                if (codec->implementation->microseconds_per_packet / 1000 == 100) { /* 100 ms = 20 ms * 5 . because there is no 50 ms frame in Opus */
                                nb_frames = 5;
                }
-               toggle_fec = 1;
        }
        frame_size = (decoded_data_len / 2) / nb_frames;
        if((frame_size * nb_frames) != context->enc_frame_size) {
@@ -884,12 +883,19 @@ static switch_status_t switch_opus_encode_repacketize(switch_codec_t *codec,
        opus_repacketizer_init(rp);
        dec_ptr_buf = (int16_t *)decoded_data;
        for (i = 0; i < nb_frames; i++) {
+                /* set inband FEC ON or OFF for the next Opus frame */
+               if (i == (nb_frames - 1) && want_fec) { 
+                       /* When FEC is enabled for Opus frame N, LBRR is stored during regular encoding of */ 
+                       /* this Opus frame N, and this LBRR data will be packed with the regular encoding */
+                       /* data of Opus frame N+1. We enable FEC on our last Opus frame which is to be packed, just */
+                       /* to actually have it stored in the first Opus frame, that is when switch_opus_encode_repacketize() */
+                       /* is called again to pack the next big 80,100 or 120 ms frame. */ 
+                       toggle_fec = 1; /* FEC ON for the last frame */
+               }
+
+               opus_encoder_ctl(context->encoder_object, OPUS_SET_INBAND_FEC(toggle_fec));
                bytes = opus_encode(context->encoder_object, (opus_int16 *) dec_ptr_buf, frame_size, enc_ptr_buf, len);
-                /* set inband FEC off for the next frame to be packed, the current frame may contain FEC */
-               if (toggle_fec == 1) {
-                       toggle_fec = 0;
-                       opus_encoder_ctl(context->encoder_object, OPUS_SET_INBAND_FEC(toggle_fec));
-               } 
+
                if (bytes < 0) {
                        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "Encoder Error: %s Decoded Datalen %u Codec NumberChans %u" \
                                                          "Len %u DecodedDate %p EncodedData %p ContextEncoderObject %p enc_frame_size: %d\n",