ml
46 lines
1.8 KiB
Markdown
46 lines
1.8 KiB
Markdown
## Sound Effects
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Sound effects are stored in ```digifx.res```, which contains resources of data type ```0x07```.
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The resources have IDs in the range from ```0x00C9``` to ```0x013B```, are uncompressed and have one effect per resource.
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Each resource contains one sound effect, which is stored in the
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[Creative Voice File](http://wiki.multimedia.cx/index.php?title=Creative_Voice) format.
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Although the format would allow for different sample formats, only unsigned 8-bit PCM audio (MIME type ```audio/L8```)
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is supported and expected. The sound effects don't use any special block types of the file format,
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only one ```Sound data``` block is present, followed by a ```Terminator``` block identifier. All effects have one channel (mono).
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### Format
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The following is an extract of the above linked page, specialized to the use by the engine.
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***Sound Effect***
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0000 [19]byte Identifier text "Creative Voice File"
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0013 byte Identifier terminator: 0x1A
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0014 int16 Length of header (commonly 0x1A)
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0016 uint16 Version number (0x010A)
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0018 uint16 Version number validation
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001A byte Sound data block type: 0x01
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001B [3]byte Length of block data (sample count + 2)
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001E byte Frequency divisor
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001F byte Codec ID (audio/L8: 0x00)
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0020 []byte Samples
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NNNN byte Terminator block type: 0x00
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***Version Number***
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The version number is encoded as a major and minor number, in the high and low bytes respectively.
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The validation value is the result of building the binary complement of the version number and adding the constant ```0x1234```.
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***Frequency Divisor***
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The frequency divisor is used to calculate the sample rate with the following formula:
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```
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sampleRate := 1000000 / (256 - frequencyDivisor)
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```
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