avcodec/libwebpenc: add quality option

previously quality could only be set through qscale/global_quality but the scale
was inverted. Using a separate option avoids the confusion from qscale working
backward.
Reviewed-by: Benoit Fouet <benoit.fouet@free.fr>
Reviewed-by: Clément Bœsch <u@pkh.me>
Reviewed-by: Nicolas George <george@nsup.org>
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/libwebpenc.c

@@ -65,8 +65,7 @@ static av_cold int libwebp_encode_init(AVCodecContext *avctx)
     LibWebPContext *s = avctx->priv_data;
     int ret;
 
-    if (avctx->global_quality < 0)
-        avctx->global_quality = 75 * FF_QP2LAMBDA;
+    if (avctx->global_quality >= 0)
         s->quality = av_clipf(avctx->global_quality / (float)FF_QP2LAMBDA,
                               0.0f, 100.0f);
 
@@ -327,6 +326,7 @@ static const AVOption options[] = {
     { "text",       "text-like",                                        0, AV_OPT_TYPE_CONST, { .i64 = WEBP_PRESET_TEXT    }, 0, 0, VE, "preset" },
     { "cr_threshold","Conditional replenishment threshold",     OFFSET(cr_threshold), AV_OPT_TYPE_INT, { .i64 =  0  },  0, INT_MAX, VE           },
     { "cr_size"     ,"Conditional replenishment block size",    OFFSET(cr_size)     , AV_OPT_TYPE_INT, { .i64 =  16 },  0, 256,     VE           },
+    { "quality"     ,"Quality",                OFFSET(quality),  AV_OPT_TYPE_FLOAT, { .dbl =  75 }, 0, 100,                         VE           },
     { NULL },
 };
 

libavcodec/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR 56
 #define LIBAVCODEC_VERSION_MINOR  10
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MICRO 102
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \