shithub: libvpx

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Have vpxenc use a default kf_max_rate of 5 seconds.

Rather than using the static default maximum keyframe spacing
provided by vpx_codec_enc_config_default() set the default
value to 5 times the frame rate. Five seconds is too long for
live streaming applications, but is a compromise between seek
efficiency and giving the encoder freedom to choose keyframe
locations.

The five second value is from James Zern's suggestion in
http://article.gmane.org/gmane.comp.multimedia.webm.user/2945

Change-Id: Ib7274dc248589c433c06e68ca07232e97f7ce17f

--- a/vpxenc.c

+++ b/vpxenc.c

@@ -1517,6 +1517,7 @@

     int                       arg_ctrls[ARG_CTRL_CNT_MAX][2];

     int                       arg_ctrl_cnt;

     int                       write_webm;

+    int                       have_kf_max_dist;

 };

@@ -1883,7 +1884,10 @@

         else if (arg_match(&arg, &kf_min_dist, argi))

             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;

         else

@@ -1986,6 +1990,21 @@

 }

+static void set_default_kf_interval(struct stream_state  *stream,

+                                    struct global_config *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 = 5.0*framerate;

+    }

+}

+

+

 static void show_stream_config(struct stream_state  *stream,

                                struct global_config *global,

                                struct input_state   *input)

@@ -2400,6 +2419,8 @@

          */

         if (!global.have_framerate)

             global.framerate = input.framerate;

+

+        FOREACH_STREAM(set_default_kf_interval(stream, &global));

         /* Show configuration */

         if (global.verbose && pass == 0)