qsvenc: Provide a detailed error message if the parameters are invalid

Currently it always shows "Selected ratecontrol mode is not supported
by the QSV runtime. Choose a different mode", but sometimes it is not
accurate.
Signed-off-by: Zhong Li <zhong.li@intel.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/qsvenc.c

@@ -356,15 +356,34 @@ static int select_rc_mode(AVCodecContext *avctx, QSVEncContext *q)
     return 0;
 }
 
-static int rc_supported(QSVEncContext *q)
+static int check_enc_param(AVCodecContext *avctx, QSVEncContext *q)
 {
     mfxVideoParam param_out = { .mfx.CodecId = q->param.mfx.CodecId };
     mfxStatus ret;
 
+#define UNMATCH(x) (param_out.mfx.x != q->param.mfx.x)
+
     ret = MFXVideoENCODE_Query(q->session, &q->param, &param_out);
-    if (ret < 0 ||
-        param_out.mfx.RateControlMethod != q->param.mfx.RateControlMethod)
+
+    if (ret < 0) {
+        if (UNMATCH(CodecId))
+            av_log(avctx, AV_LOG_ERROR, "Current codec type is unsupported\n");
+        if (UNMATCH(CodecProfile))
+            av_log(avctx, AV_LOG_ERROR, "Current profile is unsupported\n");
+        if (UNMATCH(RateControlMethod))
+            av_log(avctx, AV_LOG_ERROR, "Selected ratecontrol mode is unsupported\n");
+        if (UNMATCH(LowPower))
+              av_log(avctx, AV_LOG_ERROR, "Low power mode is unsupported\n");
+        if (UNMATCH(FrameInfo.FrameRateExtN) || UNMATCH(FrameInfo.FrameRateExtN))
+              av_log(avctx, AV_LOG_ERROR, "Current frame rate is unsupported\n");
+        if (UNMATCH(FrameInfo.PicStruct))
+              av_log(avctx, AV_LOG_ERROR, "Current picture structure is unsupported\n");
+        if (UNMATCH(FrameInfo.Width) || UNMATCH(FrameInfo.Height))
+              av_log(avctx, AV_LOG_ERROR, "Current resolution is unsupported\n");
+        if (UNMATCH(FrameInfo.FourCC))
+              av_log(avctx, AV_LOG_ERROR, "Current pixel format is unsupported\n");
         return 0;
+    }
     return 1;
 }
 
@@ -639,10 +658,10 @@ FF_ENABLE_DEPRECATION_WARNINGS
 #endif
     }
 
-    if (!rc_supported(q)) {
+    if (!check_enc_param(avctx,q)) {
         av_log(avctx, AV_LOG_ERROR,
-               "Selected ratecontrol mode is not supported by the QSV "
-               "runtime. Choose a different mode.\n");
+               "some encoding parameters are not supported by the QSV "
+               "runtime. Please double check the input parameters.\n");
         return AVERROR(ENOSYS);
     }