RL2

• Samples: http://samples.mplayerhq.hu/game-formats/voyeur-rl2/

PC version of the FMV-based adult game "Voyeur" developed by Entertainment Software Partners, heavily uses custom video format for the videos stored in files with exteension .rl2 This article describes only PC-version format details, no CD-i version details is known so far. In general, video is compressed using simple RLE scheme and audio is carried in raw 8-bit format.

Trivia: According to Wikipedia, this game caused ESRB rating system to be invented.

File Format

+  0  dword  Header                -- "FORM"
+  4  dword  BackSize              -- size of the background frame
+  8  dword  Signature             -- "RLV2" or "RLV3"
+  C  dword  DataSize              -- size of the data past this point *BIG-ENDIAN*
+ 10  dword  NumFrames             -- number of frames
+ 14  word   Method                -- encoding method. ignored, zero
+ 16  word   SoundRate             -- sound sample rate in some obscure format. zero means no sound
+ 18  word   Rate                  -- sound sample rate in Hz
+ 1A  word   Channels              -- number of sound channels
+ 1C  word   DefSoundSize          -- size of the single sound chunk. see notes below
+ 1E  word   VideoBase             -- initial drawing offset within 320x200 viewport
+ 20  dword  ClrCount              -- number of used colors
+ 24  RGB    Palette[256]          -- 256 RGB triplets. full 8-bit entries
-- if Signature == "RLV3" AND BackSize <> 0
  +324 byte  BackFrame[BackSize]   -- encoded background frame. ignore VideoBase during it's decoding
--
+xxx  dword  ChunkSize[NumFrames]  -- complete size of the chunk for each frame (audio+video)
+yyy  dword  ChunkOffs[NumFrames]  -- offset of the each frame chunk from the start of file
+zzz  dword  SoundSize[NumFrames]  -- size of the audio portion in the frame chunk

-- for each frame --
+xxx  byte   Audio[SoundSize[frame_nr] & 0xFFFF]  -- raw 8-bit audio
+yyy  byte   Video[...]                           -- compressed video stream

• All numbers are little-endian (except for the DataSize).
• If sound is present (SoundRate <> 0) then fps = Rate / DefSoundSize. Otherwise, fps = 11025 / 1103.

Video Decoding

The video is always encoded in 320x200 resolution. If no background frame is present, video decoding operates as follows:

repeat
  tag = next byte of input
  tag < 0x80 : paint pixel with (tag)
  tag = 0x80 : length = next byte of input
               if length is zero - finish
               fill next (length) bytes of output with (zero)
  tag > 0x80 : length = next byte of input
               fill next (length) bytes of output with (tag & 0x7F)

For background-frame based decoding, algorithm is slightly altered (you need to decode BackFrame using the above scheme first):

repeat
  tag = next byte of input
  tag = 0x00 : copy pixel from BackFrame
  tag < 0x80 : paint pixel with (tag | 0x80)
  tag = 0x80 : length = next byte of input
               if length is zero - finish
               copy (length) pixels from BackFrame
  tag > 0x80 : length = next byte of input
               fill next (length) bytes of output with (tag | 0x80)