vaapi_encode: Add support for max QP in rate control

This was added in libva 2.1.0 (VAAPI 1.1.0).  Use AVCodecContext.qmax,
matching the existing behaviour for qmin, and clean up the defaults so
that we only pass min/max when explicitly set.

doc/encoders.texi

@@ -2588,7 +2588,8 @@ Speed / quality tradeoff: higher values are faster / worse quality.
 Size / quality tradeoff: higher values are smaller / worse quality.
 @item
 @option{qmin}
-(only: @option{qmax} is not supported)
+@item
+@option{qmax}
 @item
 @option{i_qfactor} / @option{i_quant_factor}
 @item

libavcodec/vaapi_encode.c

@@ -1436,6 +1436,9 @@ static av_cold int vaapi_encode_init_rate_control(AVCodecContext *avctx)
         .initial_qp        = 0,
         .min_qp            = (avctx->qmin > 0 ? avctx->qmin : 0),
         .basic_unit_size   = 0,
+#if VA_CHECK_VERSION(1, 1, 0)
+        .max_qp            = (avctx->qmax > 0 ? avctx->qmax : 0),
+#endif
     };
     vaapi_encode_add_global_param(avctx, &ctx->rc_params.misc,
                                   sizeof(ctx->rc_params));

libavcodec/vaapi_encode_h264.c

@@ -1033,7 +1033,8 @@ static const AVCodecDefault vaapi_encode_h264_defaults[] = {
     { "i_qoffset",      "0"   },
     { "b_qfactor",      "6/5" },
     { "b_qoffset",      "0"   },
-    { "qmin",           "0"   },
+    { "qmin",           "-1"  },
+    { "qmax",           "-1"  },
     { NULL },
 };
 

libavcodec/vaapi_encode_h265.c

@@ -1148,6 +1148,8 @@ static const AVCodecDefault vaapi_encode_h265_defaults[] = {
     { "i_qoffset",      "0"   },
     { "b_qfactor",      "6/5" },
     { "b_qoffset",      "0"   },
+    { "qmin",           "-1"  },
+    { "qmax",           "-1"  },
     { NULL },
 };
 

libavcodec/vaapi_encode_mpeg2.c

@@ -672,6 +672,8 @@ static const AVCodecDefault vaapi_encode_mpeg2_defaults[] = {
     { "b_qfactor",      "6/5" },
     { "b_qoffset",      "0"   },
     { "global_quality", "10"  },
+    { "qmin",           "-1"  },
+    { "qmax",           "-1"  },
     { NULL },
 };
 

libavcodec/vaapi_encode_vp8.c

@@ -230,6 +230,8 @@ static const AVCodecDefault vaapi_encode_vp8_defaults[] = {
     { "bf",             "0"   },
     { "g",              "120" },
     { "global_quality", "40"  },
+    { "qmin",           "-1"  },
+    { "qmax",           "-1"  },
     { NULL },
 };
 

libavcodec/vaapi_encode_vp9.c

@@ -253,6 +253,8 @@ static const AVCodecDefault vaapi_encode_vp9_defaults[] = {
     { "bf",             "0"   },
     { "g",              "250" },
     { "global_quality", "100" },
+    { "qmin",           "-1"  },
+    { "qmax",           "-1"  },
     { NULL },
 };