+This is normally set to 0x2e; bit 3 indicates that a field with the
+display-time of the subtitle is present. What the other bits do is not
+known.
+
+* Time to display the subtitle (4 bytes)
+
+This in 1/90000'th of a second. This is only present if bit 3 above is
+set. This value specifies how long the subtitle will be shown, not
+when. When the subtitle is to be shown is specified in the PTS in the
+PES header.
+
+* X position (2 bytes)
+
+* Y position (2 bytes)
+
+* Width (2 bytes)
+
+This value must be even.
+
+* Height (2 bytes)
+
+This value must be even.
+
+* Unknown (1 byte)
+
+* 4 Color Palette Entries (16 bytes)
+
+* A pallette entry has the following format:
+
+ * Y (1 byte)
+ * U (1 byte)
+ * V (1 byte)
+ * Transparency (1 byte). A 0 value means totally transparent and
+ 255 totally opaque.
+
+* Command (1 byte)
+
+ >>6: 1 shift command, (cmd>>4)&3 is the direction (0=top, 1=left, 2 = right, 3 >>= bottom)
+
+* Odd-field data offset (2 bytes)
+
+Image data is stored interlaced with the even lines first. This offset
+specifies where the first odd-line image data starts.
+
+IMAGE DATA
+
+Then subtitle image data follows the above control information. Image
+lines are interlaced. That is line 0 is comes first, then line 2, then
+line 4. After all of the even lines, comes line 1, then line 3,
+etc.. The subtitle aspect ratio is not to be scaled. It is independent
+of the aspect ratio of the underlying image which it is to be
+overlayed on top of.
+
+The image is encoded using two bits per pixel that select a palette
+entry except that value 0 starts a limited run-length encoding for
+color 0. When 0 is seen, the next two bits encode one less than
+thenumber of pixels, so we can encode run lengths from 1 to 4. These
+get filled with the color in palette entry 0.
+
+The encoding of each line is padded to a whole number of bytes. The
+first field is padded to an even byte length and the complete subtitle
+is padded to a 4-byte multiple that always include one zero byte at
+the end.
+
+================
+SUBTITLING TOOLS
+================