codecs: h264dec: Check bumping again after inserting current picture.

In order to get the lowest latency, we can add another bumping check after
inserting the current picture into the DPB immediately. That can avoid
waiting for another decoding circle of the next frame and so the latency
is lower.

Fix: #1628
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2501>

diff --git a/gst-libs/gst/codecs/gsth264decoder.c b/gst-libs/gst/codecs/gsth264decoder.c
index e3f7cab..a1b5c36 100644 (file)
--- a/gst-libs/gst/codecs/gsth264decoder.c
+++ b/gst-libs/gst/codecs/gsth264decoder.c
@@ -900,6 +900,26 @@ add_picture_to_dpb (GstH264Decoder * self, GstH264Picture * picture)
   gst_h264_dpb_add (priv->dpb, picture);
 }
 
+static void
+_bump_dpb (GstH264Decoder * self, GstH264DpbBumpMode bump_level,
+    GstH264Picture * current_picture)
+{
+  GstH264DecoderPrivate *priv = self->priv;
+
+  while (gst_h264_dpb_needs_bump (priv->dpb, current_picture, bump_level)) {
+    GstH264Picture *to_output;
+
+    to_output = gst_h264_dpb_bump (priv->dpb, FALSE);
+
+    if (!to_output) {
+      GST_WARNING_OBJECT (self, "Bumping is needed but no picture to output");
+      break;
+    }
+
+    gst_h264_decoder_do_output_picture (self, to_output);
+  }
+}
+
 static gboolean
 gst_h264_decoder_handle_frame_num_gap (GstH264Decoder * self, gint frame_num)
 {
@@ -964,19 +984,7 @@ gst_h264_decoder_handle_frame_num_gap (GstH264Decoder * self, gint frame_num)
 
     gst_h264_dpb_delete_unused (priv->dpb);
 
-    while (gst_h264_dpb_needs_bump (priv->dpb, picture,
-            GST_H264_DPB_BUMP_NORMAL_LATENCY)) {
-      GstH264Picture *to_output;
-
-      to_output = gst_h264_dpb_bump (priv->dpb, FALSE);
-
-      if (!to_output) {
-        GST_WARNING_OBJECT (self, "Bumping is needed but no picture to output");
-        break;
-      }
-
-      gst_h264_decoder_do_output_picture (self, to_output);
-    }
+    _bump_dpb (self, GST_H264_DPB_BUMP_NORMAL_LATENCY, picture);
 
     /* the picture is short term ref, add to DPB. */
     if (gst_h264_dpb_get_interlaced (priv->dpb)) {
@@ -2051,7 +2059,7 @@ gst_h264_decoder_finish_picture (GstH264Decoder * self,
   GstVideoDecoder *decoder = GST_VIDEO_DECODER (self);
   GstH264DecoderPrivate *priv = self->priv;
   gboolean ret = TRUE;
-  GstH264DpbBumpMode bump_level;
+  GstH264DpbBumpMode bump_level = get_bump_level (self);
 
   /* Finish processing the picture.
    * Start by storing previous picture data for later use */
@@ -2091,19 +2099,7 @@ gst_h264_decoder_finish_picture (GstH264Decoder * self,
     gst_h264_decoder_drain_internal (self);
   }
 
-  bump_level = get_bump_level (self);
-  while (gst_h264_dpb_needs_bump (priv->dpb, picture, bump_level)) {
-    GstH264Picture *to_output;
-
-    to_output = gst_h264_dpb_bump (priv->dpb, FALSE);
-
-    if (!to_output) {
-      GST_WARNING_OBJECT (self, "Bumping is needed but no picture to output");
-      break;
-    }
-
-    gst_h264_decoder_do_output_picture (self, to_output);
-  }
+  _bump_dpb (self, bump_level, picture);
 
   /* Add a ref to avoid the case of directly outputed and destroyed. */
   gst_h264_picture_ref (picture);
@@ -2153,6 +2149,11 @@ gst_h264_decoder_finish_picture (GstH264Decoder * self,
 
   gst_h264_picture_unref (picture);
 
+  /* For the live mode, we try to bump here to avoid waiting
+     for another decoding circle. */
+  if (priv->is_live && priv->compliance != GST_H264_DECODER_COMPLIANCE_STRICT)
+    _bump_dpb (self, bump_level, NULL);
+
   return ret;
 }