improve average framerate calculation

Change Ice204e86 identified a problem with bitrate undershoot due to
low precision in the timestamps passed to the library. This patch
takes a different approach by calculating the duration of this frame
and passing it to the library, rather than using a fixed duration
and letting the library average it out with higher precision
timestamps. This part of the fix only applies to vpxenc.

This patch also attempts to fix the problem for generic applications
that may have made the same mistake vpxenc did. Instead of
calculating this frame's duration by the difference of this frame's
and the last frame's start time, we use the end times instead. This
allows the framerate calculation to scavenge "unclaimed" time from
the last frame. For instance:

  start |  end  | calculated duration
  ======+=======+====================
    0ms    33ms   33ms
   33ms    66ms   33ms
   66ms    99ms   33ms
  100ms   133ms   34ms

Change-Id: I92be4b3518e0bd530e97f90e69e75330a4c413fc

diff --git a/vp8/encoder/onyx_if.c b/vp8/encoder/onyx_if.c
index 5f02a5a..bceb586 100644 (file)
--- a/vp8/encoder/onyx_if.c
+++ b/vp8/encoder/onyx_if.c
@@ -4972,17 +4972,16 @@ int vp8_get_compressed_data(VP8_PTR ptr, unsigned int *frame_flags, unsigned lon
 
     *frame_flags = cpi->source_frame_flags;
 
-#if CONFIG_PSNR
-
     if (cpi->source_time_stamp < cpi->first_time_stamp_ever)
+    {
         cpi->first_time_stamp_ever = cpi->source_time_stamp;
-
-#endif
+        cpi->last_end_time_stamp_seen = cpi->source_time_stamp;
+    }
 
     // adjust frame rates based on timestamps given
     if (!cm->refresh_alt_ref_frame)
     {
-        if (cpi->last_time_stamp_seen == 0)
+        if (cpi->source_time_stamp == cpi->first_time_stamp_ever)
         {
             double this_fps = 10000000.000 / (cpi->source_end_time_stamp - cpi->source_time_stamp);
 
@@ -4990,7 +4989,8 @@ int vp8_get_compressed_data(VP8_PTR ptr, unsigned int *frame_flags, unsigned lon
         }
         else
         {
-            long long nanosecs = cpi->source_time_stamp - cpi->last_time_stamp_seen;
+            long long nanosecs = cpi->source_end_time_stamp
+                - cpi->last_end_time_stamp_seen;
             double this_fps = 10000000.000 / nanosecs;
 
             vp8_new_frame_rate(cpi, (7 * cpi->oxcf.frame_rate + this_fps) / 8);
@@ -4998,6 +4998,7 @@ int vp8_get_compressed_data(VP8_PTR ptr, unsigned int *frame_flags, unsigned lon
         }
 
         cpi->last_time_stamp_seen = cpi->source_time_stamp;
+        cpi->last_end_time_stamp_seen = cpi->source_end_time_stamp;
     }
 
     if (cpi->compressor_speed == 2)

diff --git a/vp8/encoder/onyx_int.h b/vp8/encoder/onyx_int.h
index 81e32f0..134e030 100644 (file)
--- a/vp8/encoder/onyx_int.h
+++ b/vp8/encoder/onyx_int.h
@@ -399,6 +399,7 @@ typedef struct
     int inter_frame_target;
     double output_frame_rate;
     long long last_time_stamp_seen;
+    long long last_end_time_stamp_seen;
     long long first_time_stamp_ever;
 
     int ni_av_qi;

diff --git a/vpxenc.c b/vpxenc.c
index 032e2e8..b139c68 100644 (file)
--- a/vpxenc.c
+++ b/vpxenc.c
@@ -1188,7 +1188,7 @@ int main(int argc, const char **argv_)
     /* Change the default timebase to a high enough value so that the encoder
      * will always create strictly increasing timestamps.
      */
-    cfg.g_timebase.den = 100000;
+    cfg.g_timebase.den = 1000;
 
     /* Never use the library's default resolution, require it be parsed
      * from the file or set on the command line.
@@ -1544,7 +1544,7 @@ int main(int argc, const char **argv_)
             vpx_codec_iter_t iter = NULL;
             const vpx_codec_cx_pkt_t *pkt;
             struct vpx_usec_timer timer;
-            int64_t frame_start;
+            int64_t frame_start, next_frame_start;
 
             if (!arg_limit || frames_in < arg_limit)
             {
@@ -1565,9 +1565,11 @@ int main(int argc, const char **argv_)
 
             frame_start = (cfg.g_timebase.den * (int64_t)(frames_in - 1)
                           * arg_framerate.den) / cfg.g_timebase.num / arg_framerate.num;
+            next_frame_start = (cfg.g_timebase.den * (int64_t)(frames_in)
+                                * arg_framerate.den)
+                                / cfg.g_timebase.num / arg_framerate.num;
             vpx_codec_encode(&encoder, frame_avail ? &raw : NULL, frame_start,
-                             cfg.g_timebase.den * arg_framerate.den
-                             / cfg.g_timebase.num / arg_framerate.num,
+                             next_frame_start - frame_start,
                              0, arg_deadline);
             vpx_usec_timer_mark(&timer);
             cx_time += vpx_usec_timer_elapsed(&timer);