Fix divide by zero.

Raised in issue Issue # 3523:

Explicitly check p_rc->rolling_target_bits > 0 for the identified case.

Also:-

When initializing  p_rc->rolling_actual_bits and
p_rc->rolling_target_bits force to max(1,x).

In the encoder interface range check target rate > 0.

Change-Id: If7ba7e98af627227498443c2e9a739c65ec8d68b

av1/av1_cx_iface.c

diff --git a/av1/av1_cx_iface.c b/av1/av1_cx_iface.c
index 9214feb..835eb00 100644
--- a/av1/av1_cx_iface.c
+++ b/av1/av1_cx_iface.c
@@ -627,6 +627,11 @@
       ERROR(#memb " out of range [" #lo ".." #hi "]"); \
   } while (0)
 
+#define RANGE_CHECK_LO(p, memb, lo)                                     \
+  do {                                                                  \
+    if (!((p)->memb >= (lo))) ERROR(#memb " out of range [" #lo "..]"); \
+  } while (0)
+
 #define RANGE_CHECK_HI(p, memb, hi)                                     \
   do {                                                                  \
     if (!((p)->memb <= (hi))) ERROR(#memb " out of range [.." #hi "]"); \
@@ -666,6 +671,7 @@
   RANGE_CHECK(cfg, g_timebase.num, 1, cfg->g_timebase.den);
   RANGE_CHECK_HI(cfg, g_profile, MAX_PROFILES - 1);
 
+  RANGE_CHECK_LO(cfg, rc_target_bitrate, 1);
   RANGE_CHECK_HI(cfg, rc_max_quantizer, 63);
   RANGE_CHECK_HI(cfg, rc_min_quantizer, cfg->rc_max_quantizer);
   RANGE_CHECK_BOOL(extra_cfg, lossless);

av1/encoder/pass2_strategy.c

diff --git a/av1/encoder/pass2_strategy.c b/av1/encoder/pass2_strategy.c
index a9442ff..40d9b78 100644
--- a/av1/encoder/pass2_strategy.c
+++ b/av1/encoder/pass2_strategy.c
@@ -4235,7 +4235,8 @@
   twopass->kf_group_bits = AOMMAX(twopass->kf_group_bits, 0);
 
   // If the rate control is drifting consider adjustment to min or maxq.
-  if ((rc_cfg->mode != AOM_Q) && !cpi->rc.is_src_frame_alt_ref) {
+  if ((rc_cfg->mode != AOM_Q) && !cpi->rc.is_src_frame_alt_ref &&
+      (p_rc->rolling_target_bits > 0)) {
     int minq_adj_limit;
     int maxq_adj_limit;
     minq_adj_limit =

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index df86380..7defafc 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -405,10 +405,10 @@
   p_rc->rate_correction_factors[KF_STD] = 1.0;
   p_rc->bits_off_target = p_rc->starting_buffer_level;
 
-  p_rc->rolling_target_bits =
-      (int)(oxcf->rc_cfg.target_bandwidth / oxcf->input_cfg.init_framerate);
-  p_rc->rolling_actual_bits =
-      (int)(oxcf->rc_cfg.target_bandwidth / oxcf->input_cfg.init_framerate);
+  p_rc->rolling_target_bits = AOMMAX(
+      1, (int)(oxcf->rc_cfg.target_bandwidth / oxcf->input_cfg.init_framerate));
+  p_rc->rolling_actual_bits = AOMMAX(
+      1, (int)(oxcf->rc_cfg.target_bandwidth / oxcf->input_cfg.init_framerate));
 }
 
 void av1_rc_init(const AV1EncoderConfig *oxcf, RATE_CONTROL *rc) {