--- /dev/null
+$Id: cvd-subtitles.txt,v 1.1 2004/01/04 16:25:00 rocky Exp $
+The following information is culled from information from
+Julio Sanchez Fernandez (http://subhandler.sourceforge.net)
+by Rocky Bernstein.
+
+We do not have information on the subtitle format used on CVD's except
+the submux sample code and a couple of samples of dubious
+origin. Thus, the information below is result of reading some code
+whose correctness is not known and some experimentation.
+
+CVD subtitles are different in several ways from SVCD OGT subtitles
+(see see corresponding info on that.)
+
+Image comes first and meta data is at the end. So that the metadata
+can be found easily, the subtitle packet starts with two bytes
+(everything is big-endian again) that gives the total size of the
+subtitle data and the offset to the metadata - i.e. size of the image
+data plus the four bytes at the beginning.
+
+Data for single screen subtitle may come in several non-contiguous
+packets of a stream. From the scant data on the format, there is only
+only way known to detect the first packet in a subtitle. The first
+packet seems to have a valid PTS while later packets for the same
+image don't.
+
+Image data comes interlaced and is run-length encoded (RLE). Each
+field is a four-bit nibbles that is further subdivided in a two-bit
+repeat count and a two-bit color number - up to three pixels can be
+described in four bits. What a 0 repeat count means is unknown. It
+might be used for RLE extension. There is a special case of a 0
+repeat count though. When the full nibble is zero, the rest of the
+line is filled with the color value in the next nibble. It is unknown
+what happens if the color value is greater than three. The rest seems
+to use a 4-entries palette. It is not impossible that the fill-line
+complete case above is not as described and the zero repeat count
+means fill line. The sample code never produces this, so it may be
+untested.
+
+Here is information given at the start of a subtitle:
+
+SPU size 2 bytes
+metadata offset 2 bytes
+
+Although metadata information does not have to come in a fixed field
+order, every metadata field consists of a tag byte followed by
+parameters. In all cases known, the size including the tag byte is
+exactly four bytes.
+
+code Meaning
+---- -------
+0x0c Unknown
+
+0x04 24-bit subtitle duration in 1/90000ths of a second
+
+0x17 upper left x, y position, each a 10-bit value, encoded:
+ x = ((p[1]&0x0f)<<6) + (p[2]>>2)
+ y = ((p[2]&0x03)<<8) + p[3];
+
+0x1f lower right x, y postion, each a 10-bit (0-1023) value,
+ encoded as above
+
+0x24 3 bytes primary palette 0 - 1 byte for each of y, u, and v
+0x25 3 bytes primary palette 1 - 1 byte for each of y, u and v
+0x26 3 bytes primary palette 2 - 1 byte for each of y, u and v
+0x27 3 bytes primary palette 3 - 1 byte for each of y, u and v
+
+0x2c 3 bytes highlight palette 0 - 1 byte for each of y, u, and v
+0x2d 3 bytes highlight palette 1 - 1 byte for each of y, u and v
+0x2e 3 bytes highlight palette 2 - 1 byte for each of y, u and v
+0x2f 3 bytes highlight palette 3 - 1 byte for each of y, u and v
+
+0x37 3 bytes transparancy for primary palette - 1 byte for each
+ of y, u and v
+
+0x3f 3 bytes transparancy for highlight palette - 1 byte for each
+ of y, u and v
+
+0x47 Offset to start of even rows of interlaced image.
+0x4f Offset to start of odd rows of interlaced image.
+
+
+
+
+
+
+
+
+
projects / vlc / blobdiff