va: baseenc: Add a preferred_output_delay field for GPU parallel processing

The encoder can specify the a preferred_output_delay value to get better throughput
performance. The higher delay may get better HW performance, but it may increases
the encoder and pipeline latency.
When the output queue length is smaller than preferred_output_delay, the encoder
will not block to waiting for the encoding output. It will continue to prepare and
send more commands to GPU, which may improve the encoder throughput performance.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4359>

subprojects/gst-plugins-bad/sys/va/gstvabaseenc.c

@@ -32,6 +32,8 @@
 #define GST_CAT_DEFAULT gst_va_base_enc_debug
 GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
 
+#define GST_FLOW_OUTPUT_NOT_READY GST_FLOW_CUSTOM_SUCCESS_2
+
 struct _GstVaBaseEncPrivate
 {
   GstVideoInfo sinkpad_info;
@@ -73,6 +75,7 @@ gst_va_base_enc_reset_state_default (GstVaBaseEnc * base)
   base->profile = VAProfileNone;
   base->rt_format = 0;
   base->codedbuf_size = 0;
+  base->preferred_output_delay = 0;
   g_atomic_int_set (&base->reconf, FALSE);
 }
 
@@ -505,6 +508,33 @@ _push_out_one_buffer (GstVaBaseEnc * base)
   return ret;
 }
 
+static GstFlowReturn
+_try_to_push_out_one_buffer (GstVaBaseEnc * base)
+{
+  GstVideoCodecFrame *frame_out;
+  GstVaEncFrame *frame_enc;
+  VASurfaceID surface;
+  gboolean ready;
+
+  frame_out = g_queue_peek_head (&base->output_list);
+  if (frame_out == NULL)
+    return GST_FLOW_OUTPUT_NOT_READY;
+
+  frame_enc = gst_va_get_enc_frame (frame_out);
+
+  surface = gst_va_encode_picture_get_reconstruct_surface (frame_enc->picture);
+
+  ready = va_check_surface_has_status (base->display, surface, VASurfaceReady);
+
+  GST_LOG_OBJECT (base, "Output of system_frame_number %d is %s",
+      frame_out->system_frame_number, ready ? "ready" : "not ready");
+
+  if (!ready)
+    return GST_FLOW_OUTPUT_NOT_READY;
+
+  return _push_out_one_buffer (base);
+}
+
 static GstFlowReturn
 gst_va_base_enc_drain (GstVideoEncoder * venc)
 {
@@ -655,21 +685,42 @@ gst_va_base_enc_handle_frame (GstVideoEncoder * venc,
   /* pass it to reorder list and we should not use it again. */
   frame = NULL;
 
+  if (frame_encode) {
     while (frame_encode) {
       ret = base_class->encode_frame (base, frame_encode, FALSE);
       if (ret != GST_FLOW_OK)
         goto error_encode;
 
-    while (ret == GST_FLOW_OK && g_queue_get_length (&base->output_list) > 0)
+      while (ret == GST_FLOW_OK && g_queue_get_length (&base->output_list) >
+          base->preferred_output_delay)
         ret = _push_out_one_buffer (base);
 
       if (ret != GST_FLOW_OK)
         goto error_push_buffer;
 
+      /* Try to push out all ready frames. */
+      do {
+        ret = _try_to_push_out_one_buffer (base);
+      } while (ret == GST_FLOW_OK);
+      if (ret == GST_FLOW_OUTPUT_NOT_READY)
+        ret = GST_FLOW_OK;
+      if (ret != GST_FLOW_OK)
+        goto error_push_buffer;
+
       frame_encode = NULL;
       if (!base_class->reorder_frame (base, NULL, FALSE, &frame_encode))
         goto error_reorder;
     }
+  } else {
+    /* Try to push out all ready frames. */
+    do {
+      ret = _try_to_push_out_one_buffer (base);
+    } while (ret == GST_FLOW_OK);
+    if (ret == GST_FLOW_OUTPUT_NOT_READY)
+      ret = GST_FLOW_OK;
+    if (ret != GST_FLOW_OK)
+      goto error_push_buffer;
+  }
 
   return ret;
 

subprojects/gst-plugins-bad/sys/va/gstvabaseenc.h

@@ -67,6 +67,7 @@ struct _GstVaBaseEnc
   GQueue ref_list;
   GQueue output_list;
   GstVecDeque *dts_queue;
+  guint preferred_output_delay;
 
   GstVideoCodecState *input_state;
   union {