avcodec/nvenc: hardcode color characteristics for internal RGB2YUV conversion

nvenc does not appear to use these values as inputs for its built in RGB
to YUV conversion, but instead sets them on the output as-is.

Testing indicates the input is expected to be sRGB, with the output
ending up as limited range bt.470.

libavcodec/nvenc.c

@@ -1096,11 +1096,20 @@ static av_cold int nvenc_setup_h264_config(AVCodecContext *avctx)
     NV_ENC_CONFIG_H264 *h264               = &cc->encodeCodecConfig.h264Config;
     NV_ENC_CONFIG_H264_VUI_PARAMETERS *vui = &h264->h264VUIParameters;
 
-    vui->colourMatrix = IS_GBRP(ctx->data_pix_fmt) ? AVCOL_SPC_RGB : avctx->colorspace;
-    vui->colourPrimaries = avctx->color_primaries;
-    vui->transferCharacteristics = avctx->color_trc;
-    vui->videoFullRangeFlag = (avctx->color_range == AVCOL_RANGE_JPEG
-        || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ420P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ422P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ444P);
+    const AVPixFmtDescriptor *pixdesc = av_pix_fmt_desc_get(ctx->data_pix_fmt);
+
+    if ((pixdesc->flags & AV_PIX_FMT_FLAG_RGB) && !IS_GBRP(ctx->data_pix_fmt)) {
+        vui->colourMatrix = AVCOL_SPC_BT470BG;
+        vui->colourPrimaries = avctx->color_primaries;
+        vui->transferCharacteristics = avctx->color_trc;
+        vui->videoFullRangeFlag = 0;
+    } else {
+        vui->colourMatrix = IS_GBRP(ctx->data_pix_fmt) ? AVCOL_SPC_RGB : avctx->colorspace;
+        vui->colourPrimaries = avctx->color_primaries;
+        vui->transferCharacteristics = avctx->color_trc;
+        vui->videoFullRangeFlag = (avctx->color_range == AVCOL_RANGE_JPEG
+            || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ420P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ422P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ444P);
+    }
 
     vui->colourDescriptionPresentFlag =
         (vui->colourMatrix != 2 || vui->colourPrimaries != 2 || vui->transferCharacteristics != 2);
@@ -1208,11 +1217,20 @@ static av_cold int nvenc_setup_hevc_config(AVCodecContext *avctx)
     NV_ENC_CONFIG_HEVC *hevc               = &cc->encodeCodecConfig.hevcConfig;
     NV_ENC_CONFIG_HEVC_VUI_PARAMETERS *vui = &hevc->hevcVUIParameters;
 
-    vui->colourMatrix = IS_GBRP(ctx->data_pix_fmt) ? AVCOL_SPC_RGB : avctx->colorspace;
-    vui->colourPrimaries = avctx->color_primaries;
-    vui->transferCharacteristics = avctx->color_trc;
-    vui->videoFullRangeFlag = (avctx->color_range == AVCOL_RANGE_JPEG
-        || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ420P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ422P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ444P);
+    const AVPixFmtDescriptor *pixdesc = av_pix_fmt_desc_get(ctx->data_pix_fmt);
+
+    if ((pixdesc->flags & AV_PIX_FMT_FLAG_RGB) && !IS_GBRP(ctx->data_pix_fmt)) {
+        vui->colourMatrix = AVCOL_SPC_BT470BG;
+        vui->colourPrimaries = avctx->color_primaries;
+        vui->transferCharacteristics = avctx->color_trc;
+        vui->videoFullRangeFlag = 0;
+    } else {
+        vui->colourMatrix = IS_GBRP(ctx->data_pix_fmt) ? AVCOL_SPC_RGB : avctx->colorspace;
+        vui->colourPrimaries = avctx->color_primaries;
+        vui->transferCharacteristics = avctx->color_trc;
+        vui->videoFullRangeFlag = (avctx->color_range == AVCOL_RANGE_JPEG
+            || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ420P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ422P || ctx->data_pix_fmt == AV_PIX_FMT_YUVJ444P);
+    }
 
     vui->colourDescriptionPresentFlag =
         (vui->colourMatrix != 2 || vui->colourPrimaries != 2 || vui->transferCharacteristics != 2);