vp9: set kf_max_dist to a reasonable default (128)

the same as vp8, with the same reasoning from:
2a0d7b1 Reduce the default kf_max_dist to 128.

see also:
https://trac.ffmpeg.org/ticket/4904
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815673

+ restore vpxenc behavior of taking the library default rather than
  forcing 5s

This change also exposes an issue with one-pass svc in cbr mode, keep
the old default in datarate_test.cc for now.

Change-Id: Id6d1244f42490b06fefc1a7b4e12a423a1f83e88

CHANGELOG

@@ -1,3 +1,7 @@
+Next Release
+  - Incompatible changes:
+    The VP9 encoder's default keyframe interval changed to 128 from 9999.
+
 2015-11-09 v1.5.0 "Javan Whistling Duck"
   This release improves upon the VP9 encoder and speeds up the encoding and
   decoding processes.

test/datarate_test.cc

@@ -905,6 +905,9 @@ TEST_P(DatarateOnePassCbrSvc, OnePassCbrSvc) {
   svc_params_.scaling_factor_num[1] = 288;
   svc_params_.scaling_factor_den[1] = 288;
   cfg_.rc_dropframe_thresh = 10;
+  // TODO(marpan): another test should be added for default/small kf_max_dist
+  // once https://bugs.chromium.org/p/webm/issues/detail?id=1150 is fixed.
+  cfg_.kf_max_dist = 9999;
   ::libvpx_test::I420VideoSource video("hantro_collage_w352h288.yuv", 352, 288,
                                        30, 1, 0, 200);
   // TODO(wonkap/marpan): Check that effective_datarate for each layer hits the

vp9/vp9_cx_iface.c

@@ -1566,7 +1566,7 @@ static vpx_codec_enc_cfg_map_t encoder_usage_cfg_map[] = {
       // keyframing settings (kf)
       VPX_KF_AUTO,        // g_kfmode
       0,                  // kf_min_dist
-      9999,               // kf_max_dist
+      128,                // kf_max_dist
 
       VPX_SS_DEFAULT_LAYERS,  // ss_number_layers
       {0},

vpxenc.c

@@ -804,7 +804,6 @@ struct stream_config {
   int                       arg_ctrls[ARG_CTRL_CNT_MAX][2];
   int                       arg_ctrl_cnt;
   int                       write_webm;
-  int                       have_kf_max_dist;
 #if CONFIG_VP9_HIGHBITDEPTH
   // whether to use 16bit internal buffers
   int                       use_16bit_internal;
@@ -1224,7 +1223,6 @@ static int parse_stream_params(struct VpxEncoderConfig *global,
       config->cfg.kf_min_dist = arg_parse_uint(&arg);
     } else if (arg_match(&arg, &kf_max_dist, argi)) {
       config->cfg.kf_max_dist = arg_parse_uint(&arg);
-      config->have_kf_max_dist = 1;
     } else if (arg_match(&arg, &kf_disabled, argi)) {
       config->cfg.kf_mode = VPX_KF_DISABLED;
 #if CONFIG_VP9_HIGHBITDEPTH
@@ -1352,19 +1350,6 @@ static void set_stream_dimensions(struct stream_state *stream,
   }
 }
 
-
-static void set_default_kf_interval(struct stream_state *stream,
-                                    struct VpxEncoderConfig *global) {
-  /* Use a max keyframe interval of 5 seconds, if none was
-   * specified on the command line.
-   */
-  if (!stream->config.have_kf_max_dist) {
-    double framerate = (double)global->framerate.num / global->framerate.den;
-    if (framerate > 0.0)
-      stream->config.cfg.kf_max_dist = (unsigned int)(5.0 * framerate);
-  }
-}
-
 static const char* file_type_to_string(enum VideoFileType t) {
   switch (t) {
     case FILE_TYPE_RAW: return "RAW";
@@ -2086,8 +2071,6 @@ int main(int argc, const char **argv_) {
                      stream->config.cfg.g_timebase.num = global.framerate.den);
     }
 
-    FOREACH_STREAM(set_default_kf_interval(stream, &global));
-
     /* Show configuration */
     if (global.verbose && pass == 0)
       FOREACH_STREAM(show_stream_config(stream, &global, &input));