From 99ebbf72ef01b5155c7e2bfa40c0beaaaabfcf52 Mon Sep 17 00:00:00 2001
From: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date: Fri, 29 Jan 2021 09:43:07 -0500
Subject: [PATCH] v4l2codecs: h264: Enable 1 frame delay on non-live

When doing non-live decoding, enable 1 frame of delay. This will ensure
that we queue the next decoding job before we actually wait for the previous
to complete. This improves throughput notably on RK3399.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1881>
---
 sys/v4l2codecs/gstv4l2codech264dec.c | 27 +++++++++++++++++++++++++--
 sys/v4l2codecs/gstv4l2decoder.c      |  4 ++--
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/sys/v4l2codecs/gstv4l2codech264dec.c b/sys/v4l2codecs/gstv4l2codech264dec.c
index ca3662d3d0..d8cab64f3f 100644
--- a/sys/v4l2codecs/gstv4l2codech264dec.c
+++ b/sys/v4l2codecs/gstv4l2codech264dec.c
@@ -323,7 +323,7 @@ gst_v4l2_codec_h264_dec_decide_allocation (GstVideoDecoder * decoder,
     GstQuery * query)
 {
   GstV4l2CodecH264Dec *self = GST_V4L2_CODEC_H264_DEC (decoder);
-  guint min = 0;
+  guint min = 0, num_bitstream;
 
   self->has_videometa = gst_query_find_allocation_meta (query,
       GST_VIDEO_META_API_TYPE, NULL);
@@ -336,8 +336,11 @@ gst_v4l2_codec_h264_dec_decide_allocation (GstVideoDecoder * decoder,
 
   min = MAX (2, min);
 
+  num_bitstream = 1 +
+      MAX (1, gst_v4l2_decoder_get_render_delay (self->decoder));
+
   self->sink_allocator = gst_v4l2_codec_allocator_new (self->decoder,
-      GST_PAD_SINK, 2);
+      GST_PAD_SINK, num_bitstream);
   self->src_allocator = gst_v4l2_codec_allocator_new (self->decoder,
       GST_PAD_SRC, self->min_pool_size + min + 4);
   self->src_pool = gst_v4l2_codec_pool_new (self->src_allocator, &self->vinfo);
@@ -1066,6 +1069,24 @@ gst_v4l2_codec_h264_dec_end_picture (GstH264Decoder * decoder,
   return gst_v4l2_codec_h264_dec_submit_bitstream (self, picture, 0);
 }
 
+static guint
+gst_v4l2_codec_h264_dec_get_preferred_output_delay (GstH264Decoder * decoder,
+    gboolean live)
+{
+  GstV4l2CodecH264Dec *self = GST_V4L2_CODEC_H264_DEC (decoder);
+  guint delay;
+
+  if (live)
+    delay = 0;
+  else
+    /* Just one for now, perhaps we can make this configurable in the future. */
+    delay = 1;
+
+  gst_v4l2_decoder_set_render_delay (self->decoder, delay);
+
+  return delay;
+}
+
 static void
 gst_v4l2_codec_h264_dec_set_flushing (GstV4l2CodecH264Dec * self,
     gboolean flushing)
@@ -1222,6 +1243,8 @@ gst_v4l2_codec_h264_dec_subclass_init (GstV4l2CodecH264DecClass * klass,
       GST_DEBUG_FUNCPTR (gst_v4l2_codec_h264_dec_decode_slice);
   h264decoder_class->end_picture =
       GST_DEBUG_FUNCPTR (gst_v4l2_codec_h264_dec_end_picture);
+  h264decoder_class->get_preferred_output_delay =
+      GST_DEBUG_FUNCPTR (gst_v4l2_codec_h264_dec_get_preferred_output_delay);
 
   klass->device = device;
   gst_v4l2_decoder_install_properties (gobject_class, PROP_LAST, device);
diff --git a/sys/v4l2codecs/gstv4l2decoder.c b/sys/v4l2codecs/gstv4l2decoder.c
index c145d65714..da0300e478 100644
--- a/sys/v4l2codecs/gstv4l2decoder.c
+++ b/sys/v4l2codecs/gstv4l2decoder.c
@@ -915,7 +915,7 @@ gst_v4l2_decoder_alloc_sub_request (GstV4l2Decoder * self,
   return request;
 }
 
-/**
+/*
  * gst_v4l2_decoder_set_render_delay:
  * @self a #GstV4l2Decoder pointer
  * @delay The expected render delay
@@ -933,7 +933,7 @@ gst_v4l2_decoder_set_render_delay (GstV4l2Decoder * self, guint delay)
   self->render_delay = delay;
 }
 
-/**
+/*
  * gst_v4l2_decoder_get_render_delay:
  * @self a #GstV4l2Decoder pointer
  *