From 0b949ec07c590c1f03d6722961739f8b046c7143 Mon Sep 17 00:00:00 2001
From: He Junyan <junyan.he@intel.com>
Date: Wed, 28 Jul 2021 23:19:15 +0800
Subject: [PATCH] codecs: h264dec: Improve the fast bump for the live mode.

We control the policy of fast bump by the profile and the compliance
property. For baseline and constrained baseline profiles, we can use
more radical bump policy. User can also change the bump policy by
setting the compliance property in run time.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2432>
---
 gst-libs/gst/codecs/gsth264decoder.c | 41 ++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/gst-libs/gst/codecs/gsth264decoder.c b/gst-libs/gst/codecs/gsth264decoder.c
index 2ac022b..bded2c3 100644
--- a/gst-libs/gst/codecs/gsth264decoder.c
+++ b/gst-libs/gst/codecs/gsth264decoder.c
@@ -82,6 +82,7 @@ struct _GstH264DecoderPrivate
 {
   GstH264DecoderCompliance compliance;
 
+  guint8 profile_idc;
   gint width, height;
 
   /* input codec_data, if any */
@@ -408,6 +409,7 @@ gst_h264_decoder_reset (GstH264Decoder * self)
   g_clear_pointer (&priv->dpb, gst_h264_dpb_free);
   gst_h264_picture_clear (&priv->last_field);
 
+  priv->profile_idc = 0;
   priv->width = 0;
   priv->height = 0;
   priv->nal_length_size = 4;
@@ -962,7 +964,8 @@ 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, FALSE)) {
+    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);
@@ -2010,6 +2013,37 @@ gst_h264_decoder_reference_picture_marking (GstH264Decoder * self,
   return gst_h264_decoder_sliding_window_picture_marking (self, picture);
 }
 
+static GstH264DpbBumpMode
+get_bump_level (GstH264Decoder * self)
+{
+  GstH264DecoderPrivate *priv = self->priv;
+
+  /* User set the mode explicitly. */
+  switch (priv->compliance) {
+    case GST_H264_DECODER_COMPLIANCE_STRICT:
+      return GST_H264_DPB_BUMP_NORMAL_LATENCY;
+    case GST_H264_DECODER_COMPLIANCE_NORMAL:
+      return GST_H264_DPB_BUMP_LOW_LATENCY;
+    case GST_H264_DECODER_COMPLIANCE_FLEXIBLE:
+      return GST_H264_DPB_BUMP_VERY_LOW_LATENCY;
+    default:
+      break;
+  }
+
+  /* GST_H264_DECODER_COMPLIANCE_AUTO case. */
+
+  if (priv->is_live) {
+    /* The baseline and constrained-baseline profiles do not have B frames
+       and do not use the picture reorder, safe to use the higher bump level. */
+    if (priv->profile_idc == GST_H264_PROFILE_BASELINE)
+      return GST_H264_DPB_BUMP_VERY_LOW_LATENCY;
+
+    return GST_H264_DPB_BUMP_LOW_LATENCY;
+  }
+
+  return GST_H264_DPB_BUMP_NORMAL_LATENCY;
+}
+
 static gboolean
 gst_h264_decoder_finish_picture (GstH264Decoder * self,
     GstH264Picture * picture)
@@ -2017,6 +2051,7 @@ gst_h264_decoder_finish_picture (GstH264Decoder * self,
   GstVideoDecoder *decoder = GST_VIDEO_DECODER (self);
   GstH264DecoderPrivate *priv = self->priv;
   gboolean ret = TRUE;
+  GstH264DpbBumpMode bump_level;
 
   /* Finish processing the picture.
    * Start by storing previous picture data for later use */
@@ -2056,7 +2091,8 @@ gst_h264_decoder_finish_picture (GstH264Decoder * self,
     gst_h264_decoder_drain_internal (self);
   }
 
-  while (gst_h264_dpb_needs_bump (priv->dpb, picture, priv->is_live)) {
+  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);
@@ -2392,6 +2428,7 @@ gst_h264_decoder_process_sps (GstH264Decoder * self, GstH264SPS * sps)
       return FALSE;
     }
 
+    priv->profile_idc = sps->profile_idc;
     priv->width = sps->width;
     priv->height = sps->height;
 
-- 
2.7.4