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Parser library for 8SVX: digitally sampled audio voices consisting of 8-bit samples

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lib8svx
=======
`lib8svx` is a portable parser library built on top of `libiff`, for 8SVX
files containing digitally sampled audio voices consisting of 8-bit samples.
The 8SVX file format is frequently used on the Commodore Amiga. This library
offers the following features:

* Reading 8SVX files
* Programmatically creating 8SVX files
* Retrieving 8SVX file contents
* Writing 8SVX files
* 8SVX conformance checking
* Fibonacci delta compression of 8SVX files

This parser library implements support for all chunks described in the 8SVX
specification, which can be found in: `doc/8SVX.doc` included in this package.

Prerequisites
=============
In order to build and use this package, the following libraries are required:

* `libiff`, in order to parse IFF files

Installation on Unix-like systems
=================================
Compilation and installation of this library on Unix-like systems is straight
forward, by using the standard GNU autotools build instructions:

```bash
$ ./configure
$ make
$ make install
```

More details about the installation process can be found in the `INSTALL` file
included in this package.

Building with Visual C++
========================
This package can also be built with Visual C++ for Windows platforms. The
solution file resides in `src/lib8svx.sln` that can be opened in Visual Studio
to edit or build it. Alternatively, you can also use `MSBuild` to compile it:

```
$ MSBuild lib8svx.sln
```

To make any builds work you must have built `libiff` first. By default, the
project file looks for the `libiff` folder that resides in the parent directory
of the current solution.

You can also specify the location of the `libiff` includes and `libiff` libraries
through property parameters:

```
$ MSBuild /p:libiffIncludePath:..\..\..\libiff\src /p:libiffLibPath:..\..\..\libiff\src\Debug lib8svx.sln
```

The output is produced in the `Debug/` directory.

Portability
===========
Because this package is implemented in ANSI C (with the small exception that the
command line utilities use `getopt()` ), it should be fairly easy to port this
package to new platforms. So far it has been tested on the following platforms:

* Linux (`i686-linux`, `x86_64-linux`) using GCC
* Cygwin (`i686-cygwin`, `x86_64-cygwin`) using GCC
* AmigaOS (`m68k-amigaos`) using EGCS through Geek Gadgets
* Windows (`i686-windows`) using Visual C++ 2013

License
=======
This library is available under the MIT license

Using the 8SVX library API
==========================
The 8SVX parser provdes a convenient interface which can be used to create,
read, write and check 8SVX files. Full API documentation can be found in the
`doc/apidox` directory of this package.

Reading 8SVX files
------------------
To read a 8SVX file, call the `_8SVX_read()` function. An IFF file may contain
multiple 8SVX instruments (however most IFF files represent a single 8SVX file).
The `_8SVX_extractInstruments()` function extracts all the 8SVX instruments from
an IFF file and returns an array of `_8SVX_Instrument` struct instances, which can
be used to convienently access its properties. The length of the array is stored
in the `instrumentsLength` variable:

```C
#include <lib8svx/8svx.h>
#include <lib8svx/8svxinstrument.h>

int main(int argc, char *argv[])
{
    unsigned int instrumentsLength;
    IFF_Chunk *chunk = _8SVX_read("input.8SVX");
    _8SVX_Instrument **instrument = _8SVX_extractInstruments(chunk, &instrumentsLength);

/* Retrieve an instrument from the array and access its properties here */

return 0;
}
```

Programmatically creating 8SVX files
------------------------------------
An 8SVX file can be created by creating an instance of an `_8SVX_Instrument`
struct and by setting its sub chunks. The following example defines a 8SVX
instrument with a voice 8 header chunk:

```C
#include <lib8svx/8svxinstrument.h>

static _8SVX_Voice8Header *createCustomVoice8Header(void)
{
    _8SVX_Voice8Header *voice8Header = _8SVX_createVoice8Header();

/* Create voice 8 header properties */

voice8Header->oneShotHiSamples = SAMPLE_LENGTH;
    voice8Header->repeatHiSamples = 0;
    voice8Header->samplesPerHiCycle = 0;
    voice8Header->samplesPerSec = SAMPLE_LENGTH;
    voice8Header->ctOctave = 1;
    voice8Header->sCompression = _8SVX_CMP_NONE;
    voice8Header->volume = _8SVX_MAX_VOLUME;

return voice8Header;
}

int main(int argc, char *argv[])
{
    _8SVX_Instrument *instrument = _8SVX_createInstrument();

/* Attach voice 8 header to the instrument */
    instrument->voice8Header = createCustomVoice8Header();

return 0;
}
```

Retrieving 8SVX file contents
-----------------------------
To retrieve properties of 8SVX instruments inside an IFF file, you must take all
possible 8SVX FORMs into account, which can be retrieved through the
`_8SVX_extractInstruments()` function. By iterating over the resulting array,
you can retrieve the 8SVX instrument properties by accessing members of each
individual `_8SVX_Instrument` struct instance.

Since 8SVX instruments may have multiple octaves, the `_8SVX_extractSamples()`
function can be used to retrieve to address them in a convenient manner.

```C
#include <lib8svx/8svxinstrument.h>

int main(int argc, char *argv[])
{
    _8SVX_Instrument **instruments;
    unsigned int i, instrumentsLength, samplesLength;
    _8SVX_Sample *samples;

/* Open and extract 8SVX instruments here */

for(i = 0; i < instrumentsLength; i++)
    {
        _8SVX_Instrument *instrument = instruments[i];
        _8SVX_Voice8Header *voice8Header = instrument->voice8Header; /* Struct representing voice 8 header properties */
        _8SVX_Copyright *copyright = instrument->copyright; /* Struct containing copyright information */
        _8SVX_Body *body = instrument->body; /* Body chunk containing compressed or uncompressed sample data */

/* Retrieve more properties here */

samples = _8SVX_extractSamples(instrument, &samplesLength); /* Extract samples for each instrument octave */
    }

return 0;
}
```

Writing 8SVX files
------------------
To write an `_8SVX_Instrument` struct instance to a file, it must first be
converted to an IFF FORM using the `_8SVX_convertInstrumentToForm()` function.
Then the resulting FORM can written to disk using the `_8SVX_write()` function.

```C
#include <lib8svx/8svxinstrument.h>
#include <lib8svx/8svx.h>

int main(int argc, char *argv[])
{
    _8SVX_Instrument *instrument;
    IFF_Form *form;

/* Create a 8SVX instrument here */

form = _8SVX_convertInstrumentToForm(instrument);

if(_8SVX_write("output.8SVX", (IFF_Chunk*)form))
        return 0; /* File has been successfully written */
    else
        return 1; /* Writing failed */
}
```

8SVX conformance checking
-------------------------
Typically when opening an IFF file containing 8SVX instruments, you want to check
whether the file is valid. This can be done by invoking the
`_8SVX_checkInstruments()` function, which checks whether the IFF file is valid
and it checks whether are required 8SVX chunks are present.

```C
#include <lib8svx/8svxinstrument.h>

int main(int argc, char *argv[])
{
    IFF_Chunk *chunk;
    _8SVX_Instrument **instruments;
    unsigned int instrumentsLength;

/* Open an IFF file and extract 8SVX instruments here */

if(_8SVX_checkInstruments(chunks, instruments, instrumentsLength))
        return 0; /* IFF file including 8SVX instruments are valid */
    else
        return 1; /* IFF file including 8SVX instruments are not valid */
}
```

Fibonacci delta compression of 8SVX files
-----------------------------------------
Optionally, 8SVX files can be compressed using the Fibonacci delta compression
method, which reduces the size of the samples by 50% at some loss of quality.
A body of an instrument can be compressed by invoking the
`_8SVX_packFibonacciDelta()` function. Uncompression can be done by invoking
the `_8SVX_unpackFibonacciDelta()` function.

```C
#include <lib8svx/8svxinstrument.h>
#include <lib8svx/fibdelta.h>

int main(int argc, char *argv[])
{
    _8SVX_Instrument *instrument;

/* Create or open a 8SVX file here */

_8SVX_packFibonacciDelta(instrument); /* Instrument body is now fibonacci delta compressed */
    _8SVX_unpackFibonacciDelta(instrument); /* Instrument body is now uncompressed */

return 0;
}
```

Command-line utilities
======================
Apart from an API to handle 8SVX files, this package also includes a number of
command-line utilities to make usage of 8SVX files more convenient:

* `8svxpp` can be used to pretty print a 8SVX file into a textual representation, so that it can be manually inspected
* `8svxpack` can be used to compress or decompress all 8SVX instruments in an IFF file.

Consult the manual pages of these tools for more information.

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