lavfi/vf_scale_vaapi: add scaling mode setting support.

before this change, scale_vaapi hard coding the scaling mode, add a
new option "mode" to setting the scaling mode, it can be use to change
scaling algorithm for performance/quality trade off.

Note: VA_FILTER_SCALING_NL_ANAMORPHIC(nolinear ananorphic scaling
algorithm) doesn't support by i965/iHD driver now, add this just for
completeness.
Reviewed-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: Jun Zhao <mypopydev@gmail.com>

libavfilter/vf_scale_vaapi.c

@@ -35,10 +35,27 @@ typedef struct ScaleVAAPIContext {
 
     char *output_format_string;
 
+    int   mode;
+
     char *w_expr;      // width expression string
     char *h_expr;      // height expression string
 } ScaleVAAPIContext;
 
+static const char *scale_vaapi_mode_name(int mode)
+{
+    switch (mode) {
+#define D(name) case VA_FILTER_SCALING_ ## name: return #name
+        D(DEFAULT);
+        D(FAST);
+        D(HQ);
+        D(NL_ANAMORPHIC);
+#undef D
+    default:
+        return "Invalid";
+    }
+}
+
+
 static int scale_vaapi_config_output(AVFilterLink *outlink)
 {
     AVFilterLink *inlink     = outlink->src->inputs[0];
@@ -70,6 +87,7 @@ static int scale_vaapi_filter_frame(AVFilterLink *inlink, AVFrame *input_frame)
     AVFilterContext *avctx   = inlink->dst;
     AVFilterLink *outlink    = avctx->outputs[0];
     VAAPIVPPContext *vpp_ctx = avctx->priv;
+    ScaleVAAPIContext *ctx   = avctx->priv;
     AVFrame *output_frame    = NULL;
     VASurfaceID input_surface, output_surface;
     VAProcPipelineParameterBuffer params;
@@ -119,7 +137,7 @@ static int scale_vaapi_filter_frame(AVFilterLink *inlink, AVFrame *input_frame)
     params.output_color_standard = params.surface_color_standard;
 
     params.pipeline_flags = 0;
-    params.filter_flags = VA_FILTER_SCALING_HQ;
+    params.filter_flags = ctx->mode;
 
     err = ff_vaapi_vpp_render_picture(avctx, &params, output_surface);
     if (err < 0)
@@ -131,9 +149,10 @@ static int scale_vaapi_filter_frame(AVFilterLink *inlink, AVFrame *input_frame)
 
     av_frame_free(&input_frame);
 
-    av_log(avctx, AV_LOG_DEBUG, "Filter output: %s, %ux%u (%"PRId64").\n",
+    av_log(avctx, AV_LOG_DEBUG, "Filter output: %s, %ux%u (%"PRId64"), mode: %s.\n",
            av_get_pix_fmt_name(output_frame->format),
-           output_frame->width, output_frame->height, output_frame->pts);
+           output_frame->width, output_frame->height, output_frame->pts,
+           scale_vaapi_mode_name(ctx->mode));
 
     return ff_filter_frame(outlink, output_frame);
 
@@ -174,6 +193,17 @@ static const AVOption scale_vaapi_options[] = {
       OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, .flags = FLAGS },
     { "format", "Output video format (software format of hardware frames)",
       OFFSET(output_format_string), AV_OPT_TYPE_STRING, .flags = FLAGS },
+    { "mode", "Scaling mode",
+      OFFSET(mode), AV_OPT_TYPE_INT, { .i64 = VA_FILTER_SCALING_HQ },
+      0, VA_FILTER_SCALING_NL_ANAMORPHIC, FLAGS, "mode" },
+        { "default", "Use the default (depend on the driver) scaling algorithm",
+          0, AV_OPT_TYPE_CONST, { .i64 = VA_FILTER_SCALING_DEFAULT }, 0, 0, FLAGS, "mode" },
+        { "fast", "Use fast scaling algorithm",
+          0, AV_OPT_TYPE_CONST, { .i64 = VA_FILTER_SCALING_FAST }, 0, 0, FLAGS, "mode" },
+        { "hq", "Use high quality scaling algorithm",
+          0, AV_OPT_TYPE_CONST, { .i64 = VA_FILTER_SCALING_HQ }, 0, 0, FLAGS,  "mode" },
+        { "nl_anamorphic", "Use nolinear anamorphic scaling algorithm",
+          0, AV_OPT_TYPE_CONST, { .i64 = VA_FILTER_SCALING_NL_ANAMORPHIC }, 0, 0, FLAGS,  "mode" },
     { NULL },
 };