Distinguish the error reporting for the cases of wrong size and wrong

timebase in the video4linux2 v4l2_read_header() function.

Originally committed as revision 14647 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavdevice/v4l2.c

@@ -495,9 +495,12 @@ static int v4l2_read_header(AVFormatContext *s1, AVFormatParameters *ap)
     int res, frame_rate, frame_rate_base;
     uint32_t desired_format, capabilities;
 
-    if (ap->width <= 0 || ap->height <= 0 || ap->time_base.den <= 0) {
-        av_log(s1, AV_LOG_ERROR, "Missing/Wrong width, height or framerate\n");
-
+    if (ap->width <= 0 || ap->height <= 0) {
+        av_log(s1, AV_LOG_ERROR, "Wrong size (%dx%d)\n", ap->width, ap->height);
+        return -1;
+    }
+    if (ap->time_base.den <= 0) {
+        av_log(s1, AV_LOG_ERROR, "Wrong time base (%d)\n", ap->time_base.den);
         return -1;
     }