The .dsp format is a common GameCube/Wii format for audio that comes with the SDK. It encodes sound using Nintendo's ADPCM codec. The same ADPCM codec is also embedded into several Retro Studios format, like AGSC; the CSMP format actually embeds the entire DSP format within it.
W 3.5 Loader Manual for 16-Bit Processors Revision 1.0, October 2003 Part Number 82-000035-04 Analog Devices, Inc. One Technology Way Norwood, Mass. DSP is short for Digital Sound Processing. DSP plugins can modify the audio and common DSP plugins are limiters, plugins that add reverb and volume normalization plugins to name just a few. SAM Party DJ, SAM Broadcaster and SOS can use DSP plugins to manipulate the audio which have full support for Winamp DSP plugins and makes it easy to use.
| To do: An explanation of how ADPCM works would be nice to have somewhere on this page. Also, a better text explanation for the decoding process to go along with the example code. |
- 2ADPCM Data
Header
Dsp Files
| Offset | Type | Size | Description |
|---|---|---|---|
| 0x0 | u32 | 4 | Sample count |
| 0x4 | u32 | 4 | ADPCM nibble count; includes frame headers |
| 0x8 | u32 | 4 | Sample rate |
| 0xC | u16 | 2 | Loop flag; 1 means looped, 0 means not looped |
| 0xE | u16 | 2 | Format; always 0 |
| 0x10 | u32 | 4 | Loop start offset |
| 0x14 | u32 | 4 | Loop end offset |
| 0x18 | u32 | 4 | Current address; always 0 |
| 0x1C | s16[16] | 2 × 16 | Decode coefficients; this is 8 pairs of signed 16-bit values |
| 0x3C | u16 | 2 | Gain; always 0 |
| 0x3E | u16 | 2 | Initial predictor/scale; always matches first frame header |
| 0x40 | s16 | 2 | Initial sample history 1 |
| 0x42 | s16 | 2 | Initial sample history 2 |
| 0x44 | u16 | 2 | Loop context predictor/scale |
| 0x46 | s16 | 2 | Loop context sample history 1 |
| 0x48 | s16 | 2 | Loop context sample history 2 |
| 0x4A | u16[11] | 2 × 11 | Reserved |
| 0x60 | End of DSP header | ||
ADPCM Data
The ADPCM audio data is split up into multiple frames. Each frame is 8 bytes; it starts with a one-byte header, then has 7 bytes (or 14 samples) of audio data. For each frame header, the bottom 4 bits are the scale value, and the top 4 bits are the coefficient index to use for the current frame.
Example C Decoding Function
vgmstream used as reference: