2 files changed, 42 insertions, 5 deletions

diff --git a/vp9/encoder/vp9_bitstream.c b/vp9/encoder/vp9_bitstream.c
index c02ae1b65..1a9d33dae 100644
--- a/vp9/encoder/vp9_bitstream.c
+++ b/vp9/encoder/vp9_bitstream.c
@@ -1772,10 +1772,30 @@ void vp9_pack_bitstream(VP9_COMP *cpi, unsigned char *dest,
 
   // When there is a key frame all reference buffers are updated using the new key frame
   if (pc->frame_type != KEY_FRAME) {
+    int refresh_mask;
+
     // Should the GF or ARF be updated using the transmitted frame or buffer
-    vp9_write_bit(&header_bc, cpi->refresh_alt_ref_frame);
-    vp9_write_bit(&header_bc, cpi->refresh_golden_frame);
-    vp9_write_bit(&header_bc, cpi->refresh_last_frame);
+    if (cpi->refresh_golden_frame && !cpi->refresh_alt_ref_frame) {
+      /* Preserve the previously existing golden frame and update the frame in
+       * the alt ref slot instead. This is highly specific to the use of
+       * alt-ref as a forward reference, and this needs to be generalized as
+       * other uses are implemented (like RTC/temporal scaling)
+       *
+       * gld_fb_idx and alt_fb_idx need to be swapped for future frames, but
+       * that happens in vp9_onyx_if.c:update_reference_frames() so that it can
+       * be done outside of the recode loop.
+       */
+      refresh_mask = (cpi->refresh_last_frame << cpi->lst_fb_idx) |
+                     (cpi->refresh_golden_frame << cpi->alt_fb_idx);
+    } else {
+      refresh_mask = (cpi->refresh_last_frame << cpi->lst_fb_idx) |
+                     (cpi->refresh_golden_frame << cpi->gld_fb_idx) |
+                     (cpi->refresh_alt_ref_frame << cpi->alt_fb_idx);
+    }
+    vp9_write_literal(&header_bc, refresh_mask, NUM_REF_FRAMES);
+    vp9_write_literal(&header_bc, cpi->lst_fb_idx, NUM_REF_FRAMES_LG2);
+    vp9_write_literal(&header_bc, cpi->gld_fb_idx, NUM_REF_FRAMES_LG2);
+    vp9_write_literal(&header_bc, cpi->alt_fb_idx, NUM_REF_FRAMES_LG2);
 
     // Indicate reference frame sign bias for Golden and ARF frames (always 0 for last frame buffer)
     vp9_write_bit(&header_bc, pc->ref_frame_sign_bias[GOLDEN_FRAME]);
diff --git a/vp9/encoder/vp9_onyx_if.c b/vp9/encoder/vp9_onyx_if.c
index 0f087df1e..c288f93ef 100644
--- a/vp9/encoder/vp9_onyx_if.c
+++ b/vp9/encoder/vp9_onyx_if.c
@@ -2573,13 +2573,30 @@ static void update_reference_frames(VP9_COMP * const cpi) {
 
   // At this point the new frame has been encoded.
   // If any buffer copy / swapping is signaled it should be done here.
-
   if (cm->frame_type == KEY_FRAME) {
     ref_cnt_fb(cm->fb_idx_ref_cnt,
                &cm->active_ref_idx[cpi->gld_fb_idx], cm->new_fb_idx);
     ref_cnt_fb(cm->fb_idx_ref_cnt,
                &cm->active_ref_idx[cpi->alt_fb_idx], cm->new_fb_idx);
-  } else { /* For non key frames */
+  } else if (cpi->refresh_golden_frame && !cpi->refresh_alt_ref_frame) {
+    /* Preserve the previously existing golden frame and update the frame in
+     * the alt ref slot instead. This is highly specific to the current use of
+     * alt-ref as a forward reference, and this needs to be generalized as
+     * other uses are implemented (like RTC/temporal scaling)
+     *
+     * The update to the buffer in the alt ref slot was signalled in
+     * vp9_pack_bitstream(), now swap the buffer pointers so that it's treated
+     * as the golden frame next time.
+     */
+    int tmp;
+
+    ref_cnt_fb(cm->fb_idx_ref_cnt,
+               &cm->active_ref_idx[cpi->alt_fb_idx], cm->new_fb_idx);
+
+    tmp = cpi->alt_fb_idx;
+    cpi->alt_fb_idx = cpi->gld_fb_idx;
+    cpi->gld_fb_idx = tmp;
+  } else { /* For non key/golden frames */
     if (cpi->refresh_alt_ref_frame) {
       ref_cnt_fb(cm->fb_idx_ref_cnt,
                  &cm->active_ref_idx[cpi->alt_fb_idx], cm->new_fb_idx);