DSM is ascii plain text. It is derived from the FCEUX FM2 format.
It consists of several key-value pairs followed by an inputlog section.
The inputlog section can be identified by its starting with a | (pipe).
The inputlog section terminates at eof.
Newlines may be \r\n or \n

Key-value pairs consist of a key identifier, followed by a space separator, followed by the value text.
Value text is always terminated by a newline, which the value text will not include.
The value text is parsed differently depending on the type of the key.
The key-value pairs may be in any order, except that the first key must be version.

Integer keys (also used for booleans, with a 1 or 0) will have a value that is a simple integer not to exceed 32bits
 - version (required) - the version of the movie file format; for now it is always 3
 - emuVersion (required) - the version of the emulator used to produce the movie
 - rerecordCount (optional) - the rerecord count

String keys have values that consist of the remainder of the key-value pair line. As a consequence, string values cannot contain newlines.
 - romFilename (required) - the name of the file used to record the movie
 - comment (optional) - simply a memo. 
     by convention, the first token in the comment value is the subject of the comment.
     by convention, subsequent comments with the same subject will have their ordering preserved and may be used to approximate multiline comments.
     by convention, the author of the movie should be stored in comment(s) with a subject of: author

Hex string keys (used for binary blobs) will have a value that is like 0x0123456789ABCDEF...
 - romChecksum (required) - this is currently unused.

GUID keys have a value which is in the standard guid format: 452DE2C3-EF43-2FA9-77AC-0677FC51543B
 - guid (required) a unique identifier for a movie, generated when the movie is created, which is used when loading a savestate to make sure it belongs to the current movie.

The inputlog section consists of lines beginning and ending with a | (pipe).
The fields are as follows, except as noted in note C.
|c|.............XXX YYY Z|

'R','L','D','U','T','S','B','A','Y','X','W','E','G'

field c is a variable length decimal integer which is a bitfield corresponding to miscellaneous input states which are valid at the start of the frame.
There are currently no valid values and so this should always be 0.

the format of the main section is as follows:

 the field begins with 13 characters which constitute a bitfield.
 any character other than ' ' or '.' means that the button was pressed.
 by convention, the following mnemonics will be used in a column to remind us of which button corresponds to which column:
   RLDUTSBAYXWEG (Right,Left,Down,Up,sTart,Select,B,A,Y,X,lshoulder,rshoulder,debuG)
 This ordering is based on FCEUX to a certain extent, and arbitrary after that.
 W and E were chosen for shoulders to suggest West and East for Left and Right.
 While the emulator supports a 'lid' button, and to some extent a 'blow' button, these are not supported in the movies.

 XXX: %03d, the x position of the stylus (0,0 topleft, 255,191 bottomright)
 YYY: %03d, the y position of the stylus
 Z: %1d, 1 if the stylus is pressed pressed; 0 if not

Additional fields after this main section may be added later without breaking the file format.

* Notes *
A. There is no key-value pair that indicates the length of the movie. This must be read by scanning the inputlog and counting the number of lines.

B. All movies start from power-on.

C. The emulator uses these framerate constants
   arm7_cycles_per_frame = 560190
   frames_per_second = 59.8261