#smv is the movie capture format of Snes9x emulators

SMV 1.43 file format description

SMV file consists of a 32-byte header and various blocks that depend on settings.

Header format:

000 4-byte signature: 53 4D 56 1A "SMV\x1A"
004 4-byte little-endian unsigned int: version number, must be 1
008 4-byte little-endian integer: movie "uid" - identifies the movie-savestate relationship, also used as the recording time in Unix epoch format
00C 4-byte little-endian unsigned int: rerecord count
010 4-byte little-endian unsigned int: number of frames
014 1-byte flags "controller mask":
    bit 0: controller 1 in use
    bit 1: controller 2 in use
    bit 2: controller 3 in use
    bit 3: controller 4 in use
    bit 4: controller 5 in use
    other: reserved, set to 0
015 1-byte flags "movie options":
    bit 0:
       if "0", movie begins from an embedded "quicksave" snapshot
       if "1", a SRAM is included instead of a quicksave; movie begins from reset
    bit 1: if "0", movie is NTSC (60 fps); if "1", movie is PAL (50 fps)
    other: reserved, set to 0
016 1-byte flags "sync options":
    bit 0: MOVIE_SYNC2_INIT_FASTROM
    other: reserved, set to 0
017 1-byte flags "sync options":
    bit 0: MOVIE_SYNC_DATA_EXISTS
       if "1", all sync options flags are defined.
       if "0", all sync options flags have no meaning.
    bit 1: MOVIE_SYNC_WIP1TIMING
    bit 2: MOVIE_SYNC_LEFTRIGHT
    bit 3: MOVIE_SYNC_VOLUMEENVX
    bit 4: MOVIE_SYNC_FAKEMUTE
    bit 5: MOVIE_SYNC_SYNCSOUND
    bit 6: MOVIE_SYNC_HASROMINFO
       if "1", there is extra ROM info located right in between of the metadata and the savestate.
    bit 7: set to 0.
018 4-byte little-endian unsigned int: offset to the savestate inside file
01C 4-byte little-endian unsigned int: offset to the controller data inside file

Metadata

After the header comes "metadata", which is UTF16-coded movie title string (author info). The metadata begins from position 32 (0x20) and ends at <savestate_offset - length_of_extra_rom_info_in_bytes>.

Extra ROM info

Extra ROM info is an optional 30-byte record which contains the following structure:

000 3 bytes of zero padding: 00 00 00 003 4-byte integer: CRC32 of the ROM 007 23-byte ascii string:

the game name copied from the ROM, truncated to 23 bytes (the game name in the ROM is 21 bytes)

Extra ROM info is always positioned right before the savestate. Its size is 30 bytes if MOVIE_SYNC_HASROMINFO is used (and MOVIE_SYNC_DATA_EXISTS is set), 0 bytes otherwise.

Savestates

The savestate offset is <32 + length_of_metadata_in_bytes + length_of_extra_rom_info_in_bytes>. At the savestate offset there is a gzip-compressed file.

• If the movie is snapshot-anchored, it is a structured Snes9x savestate.
• If the movie is reset-anchored, it is a SRAM snapshot (which should decompress into 0x20000 bytes in length).

Controller data

The controller data offset is <savestate_offset + length_of_compressed_savestate>. The controller data contains <number_of_frames + 1> frames. Each frame consists of 2 bytes per controller. So if there are 3 controllers, a frame is 6 bytes and if there is only 1 controller, a frame is 2 bytes.

Note that the savestate data must come before controller data - Snes9x uses the savestate offset to calculate the length of the metadata. A gap between the savestate data and the controller data is allowed.

Each value is determined by OR-ing together values for whichever of the following are pressed:

  01 00 (reserved)
  02 00 (reserved)
  04 00 (reserved)
  08 00 (reserved)
  10 00 R
  20 00 L
  40 00 X
  80 00 A
  00 01 Right
  00 02 Left
  00 04 Down
  00 08 Up
  00 10 Start
  00 20 Select
  00 40 Y
  00 80 B

In the reset-recording patch, a frame that contains the value FF FF for every controller denotes a reset. The reset is done through the S9xSoftReset routine.