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edb40e42e7
I started looking into how to make the APU, and boy, let me tell ya, it's going to be a massive undertaking. Undoubtedly a fun undertaking, but still... Since it's a personal goal to get Super Mario Bros 2 running before new years (after all, that game has won game-of-the-year i don't even know _how_ many years in a row), i've decided to just use Blargg's venerable `nes_snd_emu` library for now. It took some wrestling, it it's in, and it works! Almost. I still don't know why enabling the Frame IRQ kills most games, but i'll look into that! Welp, on to bigger and better things! Namely: MMC1, which will give me Zelda and... Super Mario Bros 2!
169 lines
7.1 KiB
Text
Executable file
169 lines
7.1 KiB
Text
Executable file
Nes_Snd_Emu 0.1.7 Notes
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-----------------------
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Overview
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--------
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The library includes a NES APU sound chip emulator, sound sample buffer,
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support for state snapshots, a Namco 106 sound chip emulator, a Konami VRC6
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sound chip emulator, and a nonlinear sound buffer.
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The sound chip emulators handle reads and writes to their registers and
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generate samples into one or more sound buffers. Register accesses take a CPU
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clock count, relative to the current time frame. When a time frame is ended all
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samples from it are added to the sound buffer.
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The sound buffer accumulates samples generated by the sound chips and allows
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them to be read out at any time. The sample rate can be adjusted freely.
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Using the APU
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-------------
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Simple_Apu is recommended instead of Nes_Apu when using the library for the
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first time (see Simple_Apu.h for reference). Its source code demonstrates basic
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use of the APU.
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To use Nes_Apu (or the other sound chips), its output must be routed to a
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Blip_Buffer. Then pass CPU reads and writes to the sound chip, end its time
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frame periodically and read samples from the sound buffer.
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Nes_Apu apu;
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Blip_Buffer buf;
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Setup
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buf.sample_rate() Set sample rate and allocate memory for buffer
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buf.clock_rate() Set clock rate (1789773 for NTSC NES)
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apu.output() Route APU output to buffer
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apu.dmc_reader() Set function APU calls to read memory
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Emulation
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apu.write_register() Emulate write to APU register
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apu.read_status() Emulate reads APU status register
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apu.end_frame() Generate samples for time frame
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buf.end_frame() Make samples for time frame available for reading
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buf.samples_avail() Number of samples in sound buffer
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buf.read_samples() Read samples out of sound buffer
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Nonlinear Sound Emulation
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-------------------------
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Nonlinear_Buffer is a special sound buffer which emulates the non-linearity of
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the NES APU sound chip on the triangle, noise, and DMC channels. It can be used
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in place of Blip_Buffer, except that the APU should be assigned using
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buf.enable_nonlinearity( apu ), and other sound chips using
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other_sound_chip.output( buf.buffer() ).
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Blip_Buffer
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-----------
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Basic Blip_Buffer operation is covered. Further features like frequency
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equalization and other features are not described. For more information and
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examples of using Blip_Buffer, download the full Blip_Buffer library package
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Emulation Accuracy
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------------------
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Nes_Apu accuracy has some room for improvement, especially regarding IRQ
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handling. I am still working on reverse-engineering the NES APU and designing
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an improved APU.
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Nes_Namco and Nes_Vrc6 accuracy is based on the documentation I have. I have
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made many tweaks to make them sound similar to a couple of samples I've heard
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of the real thing.
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Solving Problems
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----------------
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If you're having problems, check the following:
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- If multiple threads are being used, ensure that only one at a time is
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accessing objects from the library. This library is not thread-safe.
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- Turn the compiler's optimizer is off. Sometimes an optimizer generates bad
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code.
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- Enable debugging support. This enables assertions and other run-time checks.
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- See if the demo works. If not, contact me.
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Error handling
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--------------
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Functions which can fail have a return type of blargg_err_t, which is a pointer
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to an error string (const char*). If the function is successful it returns
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blargg_success (NULL), otherwise it returns a pointer to an error string.
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To allow compatibility with older C++ compilers, no exceptions are thrown by
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any of the modules. The library is exception-safe, and any exceptions which
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occur are not intercepted. Any exceptions thrown by the standard library or
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caller-supplied functions are not caught.
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The library uses BLARGG_NEW instead of new for allocations. By default,
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BLARGG_NEW is #defined to new (nothrow) so that a failed allocation won't cause
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an exception. This can be overriden in your config.h file (see below).
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Significant violations of the documented interface are flagged with debug-only
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assertions. Failure of these usually indicates a caller error rather than a
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defect in the library.
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Configuration
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-------------
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The header "blargg_common.h" is used to establish a common environment, and is
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#included at the beginning of all library headers and sources. It attempts to
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automatically determine the features of the environment, but might need help.
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If HAVE_CONFIG_H is defined in the compiler options, the file "config.h" is
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included at the beginning of each library header file, allowing configuration
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options for the library to be set. It's fine if other libraries also use this
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scheme, as they won't conflict.
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I have attempted to design the library so that configuration can be done
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without modifying any of the library sources and header files. This makes it
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easy to upgrade to a new version without losing any customizations to its
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configuration.
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Some parts of the library might depend on the order of bytes in multibyte
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types. If so, they will cause a compilation error if the order can't be
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determined (rather than silently fail). If this occurs, define the appropriate
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symbol. For big-endian (most significant byte first, i.e. Motorola 68000,
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PowerPC), #define BLARGG_BIG_ENDIAN to 1. For little-endian (least significant
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byte first, i.e. Intel x86), #define BLARGG_LITTLE_ENDIAN to 1.
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Older C++ compilers might not support bool. Support is provided where bool is
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not available, but the compiler's support of bool might not be properly
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determined. If errors occur in "blargg_common.h" in the bool section, #define
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BLARGG_COMPILER_HAS_BOOL to 1 if your compiler supports bool, otherwise 0.
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If your compiler doesn't support static_cast<>, #define STATIC_CAST( type ) to
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(type) so that old-style casts are used instead.
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If your compiler supports namespaces, blargg_common.h uses standard headers
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with the "c" prefix to avoid bringing names from std into the global namespace.
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If your compiler supports namespaces but this isn't being detected by
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blargg_common.h, #define BLARGG_COMPILER_HAS_NAMESPACE to 1.
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Every library source file has #include BLARGG_SOURCE_BEGIN after all other
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#include lines, to allow setting compiler options and disabling warnings for
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library sources only. By default, this is #defined to "blargg_source.h".
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In library source files, #include BLARGG_ENABLE_OPTIMIZER is used before
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performance-critical code. By default it doesn't do anything, since enabling
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compiler options involves compiler-specific #pragma directives.
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After you've got the library working, you can enable platform-specific
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optimizations by #defining BLARGG_NONPORTABLE to 1. Contact me if you encounter
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any problems that only occur when these are enabled.
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If you have any problems with "blargg_common.h", contact me.
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Boost Compatibility
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-------------------
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Boost is a collection of small, useful C++ libraries which provide basic
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services. If it's not installed in your environment or your environment isn't
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supported, a tiny substitute is included in the "boost/" directory. This
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implements only that boost functionality used, and is written to work with most
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compilers. If boost is already installed, you can delete the included "boost/"
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directory. For more information about boost, see http://boost.org/
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