doc/filters: Add ascii graphics to clarify what the currently implemented tinterlace modes do

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/filters.texi

@@ -8537,33 +8537,164 @@ Available values are:
 @item merge, 0
 Move odd frames into the upper field, even into the lower field,
 generating a double height frame at half frame rate.
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+
+Output:
+11111                           33333
+22222                           44444
+11111                           33333
+22222                           44444
+11111                           33333
+22222                           44444
+11111                           33333
+22222                           44444
+@end example
 
 @item drop_odd, 1
 Only output even frames, odd frames are dropped, generating a frame with
 unchanged height at half frame rate.
 
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+
+Output:
+                22222                           44444
+                22222                           44444
+                22222                           44444
+                22222                           44444
+@end example
+
 @item drop_even, 2
 Only output odd frames, even frames are dropped, generating a frame with
 unchanged height at half frame rate.
 
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+
+Output:
+11111                           33333
+11111                           33333
+11111                           33333
+11111                           33333
+@end example
+
 @item pad, 3
 Expand each frame to full height, but pad alternate lines with black,
 generating a frame with double height at the same input frame rate.
 
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+11111           22222           33333           44444
+
+Output:
+11111           .....           33333           .....
+.....           22222           .....           44444
+11111           .....           33333           .....
+.....           22222           .....           44444
+11111           .....           33333           .....
+.....           22222           .....           44444
+11111           .....           33333           .....
+.....           22222           .....           44444
+@end example
+
+
 @item interleave_top, 4
 Interleave the upper field from odd frames with the lower field from
 even frames, generating a frame with unchanged height at half frame rate.
 
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111<-         22222           33333<-         44444
+11111           22222<-         33333           44444<-
+11111<-         22222           33333<-         44444
+11111           22222<-         33333           44444<-
+
+Output:
+11111                           33333
+22222                           44444
+11111                           33333
+22222                           44444
+@end example
+
+
 @item interleave_bottom, 5
 Interleave the lower field from odd frames with the upper field from
 even frames, generating a frame with unchanged height at half frame rate.
 
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111           22222<-         33333           44444<-
+11111<-         22222           33333<-         44444
+11111           22222<-         33333           44444<-
+11111<-         22222           33333<-         44444
+
+Output:
+22222                           44444
+11111                           33333
+22222                           44444
+11111                           33333
+@end example
+
+
 @item interlacex2, 6
 Double frame rate with unchanged height. Frames are inserted each
 containing the second temporal field from the previous input frame and
 the first temporal field from the next input frame. This mode relies on
 the top_field_first flag. Useful for interlaced video displays with no
 field synchronisation.
+
+@example
+ ------> time
+Input:
+Frame 1         Frame 2         Frame 3         Frame 4
+
+11111           22222           33333           44444
+ 11111           22222           33333           44444
+11111           22222           33333           44444
+ 11111           22222           33333           44444
+
+Output:
+11111   22222   22222   33333   33333   44444   44444
+ 11111   11111   22222   22222   33333   33333   44444
+11111   22222   22222   33333   33333   44444   44444
+ 11111   11111   22222   22222   33333   33333   44444
+@end example
+
+
 @end table
 
 Numeric values are deprecated but are accepted for backward