avfilter/showvolume: use AV_OPT_TYPE_BOOL for channel name displaying option (t)

libavfilter/avf_showvolume.c

@@ -53,7 +53,7 @@ static const AVOption showvolume_options[] = {
     { "h", "set channel height", OFFSET(h), AV_OPT_TYPE_INT, {.i64=20}, 1, 100, FLAGS },
     { "f", "set fade",           OFFSET(f), AV_OPT_TYPE_INT, {.i64=20}, 1, 255, FLAGS },
     { "c", "set volume color expression", OFFSET(color), AV_OPT_TYPE_STRING, {.str="if(gte(VOLUME,-2), if(gte(VOLUME,-1),0xff0000ff, 0xff00ffff),0xff00ff00)"}, 0, 0, FLAGS },
-    { "t", "display channel names", OFFSET(draw_text), AV_OPT_TYPE_INT, {.i64=1}, 0, 1, FLAGS },
+    { "t", "display channel names", OFFSET(draw_text), AV_OPT_TYPE_BOOL, {.i64=1}, 0, 1, FLAGS },
     { NULL }
 };