lavf/qsv_scale: add scaling modes support

low_power mode will use a fixed HW engine (SFC), thus can offload EU usage.
high quality mode will take EU usage (AVS sampler).

Performance and EU usage (Render usage) comparsion on Intel(R) Xeon(R) CPU E3-1225 v5 @ 3.30GHz:

High quality mode : ffmpeg -hwaccel qsv -c:v h264_qsv -i bbb_sunflower_1080p_30fps_normal_2000frames.h264 \
-vf scale_qsv=w=1280:h=736:mode=hq -f null -
fps=389
RENDER usage: 28.10 (provided by MSDK metrics_monitor)

Low Power mode: ffmpeg -hwaccel qsv -c:v h264_qsv -i ~/bbb_sunflower_1080p_30fps_normal_2000frames.h264 \
-vf scale_qsv=w=1280:h=736:mode=low_power -f null -
fps=343
RENDER usage: 0.00

Low power mode (SFC) may be disabled if not supported by
MSDK/Driver/HW, and replaced by AVS mode interanlly.
Signed-off-by: Zhong Li <zhong.li@intel.com>

libavfilter/vf_scale_qsv.c

@@ -69,6 +69,8 @@ enum var_name {
     VARS_NB
 };
 
+#define QSV_HAVE_SCALING_CONFIG  QSV_VERSION_ATLEAST(1, 19)
+
 typedef struct QSVScaleContext {
     const AVClass *class;
 
@@ -88,7 +90,14 @@ typedef struct QSVScaleContext {
     int             nb_surface_ptrs_out;
 
     mfxExtOpaqueSurfaceAlloc opaque_alloc;
-    mfxExtBuffer            *ext_buffers[1];
+
+#if QSV_HAVE_SCALING_CONFIG
+    mfxExtVPPScaling         scale_conf;
+#endif
+    int                      mode;
+
+    mfxExtBuffer             *ext_buffers[1 + QSV_HAVE_SCALING_CONFIG];
+    int                      num_ext_buf;
 
     int shift_width, shift_height;
 
@@ -285,6 +294,8 @@ static int init_out_session(AVFilterContext *ctx)
     mfxStatus err;
     int i;
 
+    s->num_ext_buf = 0;
+
     /* extract the properties of the "master" session given to us */
     err = MFXQueryIMPL(device_hwctx->session, &impl);
     if (err == MFX_ERR_NONE)
@@ -357,10 +368,7 @@ static int init_out_session(AVFilterContext *ctx)
         s->opaque_alloc.Header.BufferId = MFX_EXTBUFF_OPAQUE_SURFACE_ALLOCATION;
         s->opaque_alloc.Header.BufferSz = sizeof(s->opaque_alloc);
 
-        s->ext_buffers[0] = (mfxExtBuffer*)&s->opaque_alloc;
-
-        par.ExtParam    = s->ext_buffers;
-        par.NumExtParam = FF_ARRAY_ELEMS(s->ext_buffers);
+        s->ext_buffers[s->num_ext_buf++] = (mfxExtBuffer*)&s->opaque_alloc;
 
         par.IOPattern = MFX_IOPATTERN_IN_OPAQUE_MEMORY | MFX_IOPATTERN_OUT_OPAQUE_MEMORY;
     } else {
@@ -396,6 +404,18 @@ static int init_out_session(AVFilterContext *ctx)
         par.IOPattern = MFX_IOPATTERN_IN_VIDEO_MEMORY | MFX_IOPATTERN_OUT_VIDEO_MEMORY;
     }
 
+#if QSV_HAVE_SCALING_CONFIG
+    memset(&s->scale_conf, 0, sizeof(mfxExtVPPScaling));
+    s->scale_conf.Header.BufferId     = MFX_EXTBUFF_VPP_SCALING;
+    s->scale_conf.Header.BufferSz     = sizeof(mfxExtVPPScaling);
+    s->scale_conf.ScalingMode         = s->mode;
+    s->ext_buffers[s->num_ext_buf++]  = (mfxExtBuffer*)&s->scale_conf;
+    av_log(ctx, AV_LOG_VERBOSE, "Scaling mode: %"PRIu16"\n", s->mode);
+#endif
+
+    par.ExtParam    = s->ext_buffers;
+    par.NumExtParam = s->num_ext_buf;
+
     par.AsyncDepth = 1;    // TODO async
 
     par.vpp.In  = in_frames_hwctx->surfaces[0].Info;
@@ -595,6 +615,16 @@ static const AVOption options[] = {
     { "h",      "Output video height", OFFSET(h_expr),     AV_OPT_TYPE_STRING, { .str = "ih"   }, .flags = FLAGS },
     { "format", "Output pixel format", OFFSET(format_str), AV_OPT_TYPE_STRING, { .str = "same" }, .flags = FLAGS },
 
+#if QSV_HAVE_SCALING_CONFIG
+    { "mode",      "set scaling mode",    OFFSET(mode),    AV_OPT_TYPE_INT,    { .i64 = MFX_SCALING_MODE_DEFAULT}, MFX_SCALING_MODE_DEFAULT, MFX_SCALING_MODE_QUALITY, FLAGS, "mode"},
+    { "low_power", "low power mode",        0,             AV_OPT_TYPE_CONST,  { .i64 = MFX_SCALING_MODE_LOWPOWER}, INT_MIN, INT_MAX, FLAGS, "mode"},
+    { "hq",        "high quality mode",     0,             AV_OPT_TYPE_CONST,  { .i64 = MFX_SCALING_MODE_QUALITY},  INT_MIN, INT_MAX, FLAGS, "mode"},
+#else
+    { "mode",      "(not supported)",     OFFSET(mode),    AV_OPT_TYPE_INT,    { .i64 = 0}, 0, INT_MAX, FLAGS, "mode"},
+    { "low_power", "",                      0,             AV_OPT_TYPE_CONST,  { .i64 = 1}, 0,   0,     FLAGS, "mode"},
+    { "hq",        "",                      0,             AV_OPT_TYPE_CONST,  { .i64 = 2}, 0,   0,     FLAGS, "mode"},
+#endif
+
     { NULL },
 };