libavcodec/vaapi_encode: Add async_depth to vaapi_encoder to increase performance

Fix: #7706. After commit 5fdcf85bbf, vaapi encoder's performance
decrease. The reason is that vaRenderPicture() and vaSyncBuffer() are
called at the same time (vaRenderPicture() always followed by a
vaSyncBuffer()). Now I changed them to be called in a asynchronous way,
which will make better use of hardware.
Async_depth is added to increase encoder's performance. The frames that
are sent to hardware are stored in a fifo. Encoder will sync output
after async fifo is full.

Signed-off-by: Wenbin Chen <wenbin.chen@intel.com>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>

libavcodec/vaapi_encode.h

@@ -29,6 +29,7 @@
 
 #include "libavutil/hwcontext.h"
 #include "libavutil/hwcontext_vaapi.h"
+#include "libavutil/fifo.h"
 
 #include "avcodec.h"
 #include "hwconfig.h"
@@ -47,6 +48,7 @@ enum {
     MAX_TILE_ROWS          = 22,
     // A.4.1: table A.6 allows at most 20 tile columns for any level.
     MAX_TILE_COLS          = 20,
+    MAX_ASYNC_DEPTH        = 64,
 };
 
 extern const AVCodecHWConfigInternal *const ff_vaapi_encode_hw_configs[];
@@ -297,7 +299,8 @@ typedef struct VAAPIEncodeContext {
     // Timestamp handling.
     int64_t         first_pts;
     int64_t         dts_pts_diff;
-    int64_t         ts_ring[MAX_REORDER_DELAY * 3];
+    int64_t         ts_ring[MAX_REORDER_DELAY * 3 +
+                            MAX_ASYNC_DEPTH];
 
     // Slice structure.
     int slice_block_rows;
@@ -348,6 +351,10 @@ typedef struct VAAPIEncodeContext {
 
     // Whether the driver support vaSyncBuffer
     int             has_sync_buffer_func;
+    // Store buffered pic
+    AVFifo          *encode_fifo;
+    // Max number of frame buffered in encoder.
+    int             async_depth;
 } VAAPIEncodeContext;
 
 enum {
@@ -458,7 +465,12 @@ int ff_vaapi_encode_close(AVCodecContext *avctx);
     { "b_depth", \
       "Maximum B-frame reference depth", \
       OFFSET(common.desired_b_depth), AV_OPT_TYPE_INT, \
-      { .i64 = 1 }, 1, INT_MAX, FLAGS }
+      { .i64 = 1 }, 1, INT_MAX, FLAGS }, \
+    { "async_depth", "Maximum processing parallelism. " \
+      "Increase this to improve single channel performance. This option " \
+      "doesn't work if driver doesn't implement vaSyncBuffer function.", \
+      OFFSET(common.async_depth), AV_OPT_TYPE_INT, \
+      { .i64 = 2 }, 1, MAX_ASYNC_DEPTH, FLAGS }
 
 #define VAAPI_ENCODE_RC_MODE(name, desc) \
     { #name, desc, 0, AV_OPT_TYPE_CONST, { .i64 = RC_MODE_ ## name }, \