lavf/rawvideodec: fix/extend option descriptions

libavformat/rawvideodec.c

@@ -103,9 +103,9 @@ static int rawvideo_read_packet(AVFormatContext *s, AVPacket *pkt)
 #define OFFSET(x) offsetof(RawVideoDemuxerContext, x)
 #define DEC AV_OPT_FLAG_DECODING_PARAM
 static const AVOption rawvideo_options[] = {
-    { "video_size", "A string describing frame size, such as 640x480 or hd720.", OFFSET(video_size), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
+    { "video_size", "set frame size", OFFSET(video_size), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, DEC },
-    { "pixel_format", "", OFFSET(pixel_format), AV_OPT_TYPE_STRING, {.str = "yuv420p"}, 0, 0, DEC },
+    { "pixel_format", "set pixel format", OFFSET(pixel_format), AV_OPT_TYPE_STRING, {.str = "yuv420p"}, 0, 0, DEC },
-    { "framerate", "", OFFSET(framerate), AV_OPT_TYPE_STRING, {.str = "25"}, 0, 0, DEC },
+    { "framerate", "set frame rate", OFFSET(framerate), AV_OPT_TYPE_STRING, {.str = "25"}, 0, 0, DEC },
     { NULL },
 };