Data Compression

Compressing your assets will let you fit more data on a cartridge. But which data should you compress, and how? What are the tradeoffs?

TODO: Link to decoding libraries / compression tools.

Data Compression

Any data can be compressed with a general-purpose data compression algorithm, such as Deflate. However, this is generally not as effective for media, like images, audio, or video.

Images

• Raw

• JPEG

• HVQ

Audio

TODO: Calculate bit rates at different sample rates. Find samples for comparison or create a test ROM.

The microcode and audio libraries that come with LibUltra support PCM and VADPCM. TODO: What about LibDragon?

• PCM: Baseline for comparison: 16 bits per sample. This is raw, uncompressed audio.

• VADPCM: Used in many retail Nintendo 64 games. Always 4.5 bits per sample, encoded in blocks of 16 samples.

• MP3: "Known to be possible." Used in some retail Nintendo 64 games, such as Conker's Bad Fur Day.

• Music can also be stored in MOD or MIDI format, but this is not a type of compression.

Encoding	Sample Rate	Bit rate (kbit/s)	Length per megabyte (s/MiB)	Capacity of 64 MiB cartridge (h:mm:ss)
16-bit PCM	44.1 kHz	706 kbit/s	11.9 s/MiB	12:41
	32 kHz	512 kbit/s	16.4 s/MiB	17:29
	22.05 kHz	353 kbit/s	23.8 s/MiB	25:22
	16 kHz	256 kbit/s	32.7 s/MiB	34:57
VADPCM	44.1 kHz	198 kbit/s	42.3 s/MiB	45:05
	32 kHz	144 kbit/s	58.3 s/MiB	1:02:08
	22.05 kHz	99.2 kbit/s	84.5 s/MiB	1:30:11
	16 kHz	72.0 kbit/s	117 s/MiB	2:04:17

Note that 1 MiB is 1024*1024 bytes, and 1 kbit is 1,000 bits.

Video

TODO: How easy is it to use these codecs? Are there code samples?

• HVQM: "Known to be possible." Used by some retail Nintendo 64 games.

• H.264: "Known to be possible." Giovanni Bajo is working on a port of Dragon's Lair, using H.264 for the video.