Adding is_altref_enabled() function.

Change-Id: I54cdb4ce11590511e6f86bc2fd55771f1c18a20a

vp9/encoder/vp9_encoder.c

@@ -588,8 +588,6 @@ void vp9_change_config(struct VP9_COMP *cpi, const VP9EncoderConfig *oxcf) {
 
   cpi->oxcf = *oxcf;
   cpi->pass = get_pass(cpi->oxcf.mode);
-  if (cpi->oxcf.mode == REALTIME)
-    cpi->oxcf.play_alternate = 0;
 
   rc->baseline_gf_interval = DEFAULT_GF_INTERVAL;
   cpi->ref_frame_flags = VP9_ALT_FLAG | VP9_GOLD_FLAG | VP9_LAST_FLAG;
@@ -2416,7 +2414,7 @@ int vp9_get_compressed_data(VP9_COMP *cpi, unsigned int *frame_flags,
   cpi->refresh_alt_ref_frame = 0;
 
   // Should we code an alternate reference frame.
-  if (cpi->oxcf.play_alternate && rc->source_alt_ref_pending) {
+  if (is_altref_enabled(&cpi->oxcf) && rc->source_alt_ref_pending) {
     int frames_to_arf;
 
 #if CONFIG_MULTIPLE_ARF

vp9/encoder/vp9_encoder.h

@@ -284,6 +284,10 @@ typedef struct VP9EncoderConfig {
   vp8e_tuning tuning;
 } VP9EncoderConfig;
 
+static INLINE int is_altref_enabled(const VP9EncoderConfig *cfg) {
+  return cfg->mode != REALTIME && cfg->play_alternate && cfg->lag_in_frames > 0;
+}
+
 static INLINE int is_lossless_requested(const VP9EncoderConfig *cfg) {
   return cfg->best_allowed_q == 0 && cfg->worst_allowed_q == 0;
 }

vp9/encoder/vp9_firstpass.c

@@ -1526,7 +1526,7 @@ static void define_gf_group(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
   double mv_in_out_accumulator = 0.0;
   double abs_mv_in_out_accumulator = 0.0;
   double mv_ratio_accumulator_thresh;
-  unsigned int allow_alt_ref = oxcf->play_alternate && oxcf->lag_in_frames;
+  unsigned int allow_alt_ref = is_altref_enabled(oxcf);
 
   int f_boost = 0;
   int b_boost = 0;

vp9/encoder/vp9_ratectrl.c

@@ -1129,7 +1129,7 @@ void vp9_rc_postencode_update(VP9_COMP *cpi, uint64_t bytes_used) {
 
   rc->total_target_vs_actual = rc->total_actual_bits - rc->total_target_bits;
 
-  if (oxcf->play_alternate && cpi->refresh_alt_ref_frame &&
+  if (is_altref_enabled(oxcf) && cpi->refresh_alt_ref_frame &&
       (cm->frame_type != KEY_FRAME))
     // Update the alternate reference frame stats as appropriate.
     update_alt_ref_frame_stats(cpi);
@@ -1389,8 +1389,7 @@ void vp9_rc_set_gf_max_interval(const VP9EncoderConfig *const oxcf,
   // Extended interval for genuinely static scenes
   rc->static_scene_max_gf_interval = oxcf->key_freq >> 1;
 
-  // Special conditions when alt ref frame enabled
-  if (oxcf->play_alternate && oxcf->lag_in_frames) {
+  if (is_altref_enabled(oxcf)) {
     if (rc->static_scene_max_gf_interval > oxcf->lag_in_frames - 1)
       rc->static_scene_max_gf_interval = oxcf->lag_in_frames - 1;
   }