lavfi: fix typos

Signed-off-by: Moritz Barsnick <barsnick@gmx.net>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit f4e4bde1)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/af_pan.c

@@ -109,7 +109,7 @@ static av_cold int init(AVFilterContext *ctx)
     if (!pan->args) {
         av_log(ctx, AV_LOG_ERROR,
                "pan filter needs a channel layout and a set "
-               "of channels definitions as parameter\n");
+               "of channel definitions as parameter\n");
         return AVERROR(EINVAL);
     }
     if (!args)
@@ -276,7 +276,7 @@ static int config_props(AVFilterLink *link)
     if (link->channels > MAX_CHANNELS ||
         pan->nb_output_channels > MAX_CHANNELS) {
         av_log(ctx, AV_LOG_ERROR,
-               "af_pan support a maximum of %d channels. "
+               "af_pan supports a maximum of %d channels. "
                "Feel free to ask for a higher limit.\n", MAX_CHANNELS);
         return AVERROR_PATCHWELCOME;
     }

libavfilter/vf_blackframe.c

@@ -104,8 +104,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 #define OFFSET(x) offsetof(BlackFrameContext, x)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 static const AVOption blackframe_options[] = {
-    { "amount", "Percentage of the pixels that have to be below the threshold "
-        "for the frame to be considered black.", OFFSET(bamount), AV_OPT_TYPE_INT, { .i64 = 98 }, 0, 100,     FLAGS },
+    { "amount", "percentage of the pixels that have to be below the threshold "
+        "for the frame to be considered black",  OFFSET(bamount), AV_OPT_TYPE_INT, { .i64 = 98 }, 0, 100,     FLAGS },
     { "threshold", "threshold below which a pixel value is considered black",
                                                  OFFSET(bthresh), AV_OPT_TYPE_INT, { .i64 = 32 }, 0, 255,     FLAGS },
     { "thresh", "threshold below which a pixel value is considered black",