From 241a4900842a088565db31b3913ba8ca56406042 Mon Sep 17 00:00:00 2001
From: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date: Fri, 29 Jan 2021 09:41:22 -0500
Subject: [PATCH] v4l2codecs: Add support for render delay

This add support for render delay in the decoder helper.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1881>
---
 sys/v4l2codecs/gstv4l2decoder.c | 40 +++++++++++++++++++++++++++++++++++++---
 sys/v4l2codecs/gstv4l2decoder.h |  6 ++++++
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/sys/v4l2codecs/gstv4l2decoder.c b/sys/v4l2codecs/gstv4l2decoder.c
index ba225da..c145d65 100644
--- a/sys/v4l2codecs/gstv4l2decoder.c
+++ b/sys/v4l2codecs/gstv4l2decoder.c
@@ -82,6 +82,7 @@ struct _GstV4l2Decoder
   /* properties */
   gchar *media_device;
   gchar *video_device;
+  guint render_delay;
 };
 
 G_DEFINE_TYPE_WITH_CODE (GstV4l2Decoder, gst_v4l2_decoder, GST_TYPE_OBJECT,
@@ -914,6 +915,38 @@ 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
+ *
+ * The decoder will adjust the number of allowed concurrent request in order
+ * to allow this delay. The same number of concurrent bitstream buffer will be
+ * used, so make sure to adjust the number of bitstream buffer.
+ *
+ * For per-slice decoder, this is the maximum number of pending slice, so the
+ * render backlog in frame may be less then the render delay.
+ */
+void
+gst_v4l2_decoder_set_render_delay (GstV4l2Decoder * self, guint delay)
+{
+  self->render_delay = delay;
+}
+
+/**
+ * gst_v4l2_decoder_get_render_delay:
+ * @self a #GstV4l2Decoder pointer
+ *
+ * This function is used to avoid storing the render delay in multiple places.
+ *
+ * Returns: The currently configured render delay.
+ */
+guint
+gst_v4l2_decoder_get_render_delay (GstV4l2Decoder * self)
+{
+  return self->render_delay;
+}
+
 GstV4l2Request *
 gst_v4l2_request_ref (GstV4l2Request * request)
 {
@@ -985,6 +1018,7 @@ gst_v4l2_request_queue (GstV4l2Request * request, guint flags)
 {
   GstV4l2Decoder *decoder = request->decoder;
   gint ret;
+  guint max_pending;
 
   GST_TRACE_OBJECT (decoder, "Queuing request %p.", request);
 
@@ -1014,9 +1048,9 @@ gst_v4l2_request_queue (GstV4l2Request * request, guint flags)
   gst_queue_array_push_tail (decoder->pending_requests,
       gst_v4l2_request_ref (request));
 
-  /* FIXME to support more then one pending requests, we need the request to
-   * be refcounted */
-  if (gst_queue_array_get_length (decoder->pending_requests) > 6) {
+  max_pending = MAX (1, decoder->render_delay);
+
+  if (gst_queue_array_get_length (decoder->pending_requests) > max_pending) {
     GstV4l2Request *pending_req;
 
     pending_req = gst_queue_array_peek_head (decoder->pending_requests);
diff --git a/sys/v4l2codecs/gstv4l2decoder.h b/sys/v4l2codecs/gstv4l2decoder.h
index bb34510..cfc3f66 100644
--- a/sys/v4l2codecs/gstv4l2decoder.h
+++ b/sys/v4l2codecs/gstv4l2decoder.h
@@ -108,6 +108,12 @@ GstV4l2Request   *gst_v4l2_decoder_alloc_sub_request (GstV4l2Decoder * self,
                                                       GstV4l2Request * prev_request,
                                                       GstMemory *bitstream);
 
+void              gst_v4l2_decoder_set_render_delay (GstV4l2Decoder * self,
+                                                     guint delay);
+
+guint             gst_v4l2_decoder_get_render_delay (GstV4l2Decoder * self);
+
+
 GstV4l2Request *  gst_v4l2_request_ref (GstV4l2Request * request);
 
 void              gst_v4l2_request_unref (GstV4l2Request * request);
-- 
2.7.4