Update documentation about video orientation

PR #4441 <https://github.com/Genymobile/scrcpy/pull/4441>

app/src/cli.c

@@ -2138,7 +2138,7 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                         opts->display_orientation = SC_ORIENTATION_180;
                         break;
                     case 3:
-                        // rotation 1 was 270° counterclockwise, but orientation
+                        // rotation 3 was 270° counterclockwise, but orientation
                         // is expressed clockwise
                         opts->display_orientation = SC_ORIENTATION_90;
                         break;
@@ -2531,7 +2531,8 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
         if (opts->record_orientation != SC_ORIENTATION_0) {
             if (sc_orientation_is_mirror(opts->record_orientation)) {
                 LOGE("Record orientation only supports rotation, not "
-                     "flipping: %s", optarg);
+                     "flipping: %s",
+                     sc_orientation_get_name(opts->record_orientation));
                 return false;
             }
         }

app/src/options.c

@@ -113,10 +113,10 @@ sc_orientation_apply(enum sc_orientation src, enum sc_orientation transform) {
         // In the final result, we want all the hflips then all the rotations,
         // so we must move hflip2 to the left:
         //
-        //     hflip1 × hflip2 × f(rotate1) × rotate2
+        //     hflip1 × hflip2 × rotate1' × rotate2
         //
-        // with f(rotate1) = | rotate1          if src is 0 or 180
+        // with rotate1' = | rotate1           if src is 0° or 180°
-        //                   | rotate1 + 180    if src is 90 or 270
+        //                 | rotate1 + 180°    if src is 90° or 270°
 
         src_rotation += 2;
     }

doc/video.md

@@ -130,7 +130,7 @@ scrcpy --orientation=270      # 270° clockwise
 scrcpy --orientation=flip0    # hflip
 scrcpy --orientation=flip90   # hflip + 90° clockwise
 scrcpy --orientation=flip180  # vflip (hflip + 180°)
-scrcpy --orientation=flip270  # hflip + 270°
+scrcpy --orientation=flip270  # hflip + 270° clockwise
 ```
 
 The orientation can be set separately for display and record if necessary, via