theoraenc: do not reset the encoder when we need a keyframe

Instead, remember we need a keyframe, and we will force the encoder
to emit one next time we submit a new frame.
Since libtheora does not have an API to request a keyframe, we reset
the max keyframe interval to 1 temporarily.

This has the advantage that the rate control keeps its history,
and that the encoder won't choose different quant tables or
somesuch, thus requiring new streamheaders (although this is
probably only a theoretical possibility). Should also be a
bit faster than resetting the encoder.

https://bugzilla.gnome.org/show_bug.cgi?id=663350

1 files changed, 17 insertions, 3 deletions

diff --git a/ext/theora/gsttheoraenc.c b/ext/theora/gsttheoraenc.c
index d431deb08..0823e22bc 100644
--- a/ext/theora/gsttheoraenc.c
+++ b/ext/theora/gsttheoraenc.c
@@ -940,12 +940,16 @@ theora_enc_handle_frame (GstVideoEncoder * benc, GstVideoCodecFrame * frame)
 
   {
     th_ycbcr_buffer ycbcr;
-    gint res;
+    gint res, keyframe_interval;
     GstVideoFrame vframe;
 
     if (force_keyframe) {
-      theora_enc_reset (enc);
-      theora_enc_reset_ts (enc, running_time, frame->presentation_frame_number);
+      /* if we want a keyframe, temporarily reset the max keyframe interval
+       * to 1, which will cause libtheora to emit one. There is no API to
+       * request a keyframe at the moment. */
+      keyframe_interval = 1;
+      th_encode_ctl (enc->encoder, TH_ENCCTL_SET_KEYFRAME_FREQUENCY_FORCE,
+          &keyframe_interval, sizeof (keyframe_interval));
     }
 
     if (enc->multipass_cache_fd
@@ -976,6 +980,16 @@ theora_enc_handle_frame (GstVideoEncoder * benc, GstVideoCodecFrame * frame)
 
     ret = GST_FLOW_OK;
     while (th_encode_packetout (enc->encoder, 0, &op)) {
+      /* Reset the max keyframe interval to its original state, and reset
+       * the flag so we don't create more keyframes if we loop */
+      if (force_keyframe) {
+        keyframe_interval =
+            enc->keyframe_auto ? enc->keyframe_force : enc->keyframe_freq;
+        th_encode_ctl (enc->encoder, TH_ENCCTL_SET_KEYFRAME_FREQUENCY_FORCE,
+            &keyframe_interval, sizeof (keyframe_interval));
+        force_keyframe = FALSE;
+      }
+
       ret = theora_push_packet (enc, &op);
       if (ret != GST_FLOW_OK)
         goto beach;