579 lines
19 KiB
Text
579 lines
19 KiB
Text
== Audio
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Declared in `<joey/audio.h>`.
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There are three layers, and on some platforms they share physical hardware:
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* *Module playback* -- `jlAudioPlayMod`, four-channel Protracker `.MOD`.
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* *Chip tracker* -- `jlMusicPlay`, a portable event stream driving three tone
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voices plus noise at register-write cost, with no CPU mixing. The recommended
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music path.
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* *Voices and effects* -- `jlAudioVoice`, `jlAudioNoise`, `jlAudioPlaySfx`, and
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the streaming forms.
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[WARNING]
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====
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On the Amiga the tone voices and the noise *are* the hardware the module
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player drives: Paula's four channels. While a `.MOD` plays, `jlAudioVoice` and
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`jlAudioNoise` writes fight the player's register writes and lose. On the
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plain ST (not the STe build) digital sound -- a module, an effect, or a
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stream -- plays through the sound chip's channel A, so tone voice 0 is silent
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while it plays and sounds again when it stops; voices 1 and 2 play on. Choose
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the module layer or the voice and tracker layer per scene, never both at once.
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====
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`jlInit` starts audio and `jlShutdown` stops it; a program that wants none
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sets `jlConfigT.noAudio`, and every audio call is then silent. Sound that does
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not start is not fatal: `jlInit` still succeeds, modules and sound effects are
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silent, `jlAudioTickRegister` refuses, and the log says so. The tone and noise
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voices, and so `jlMusicPlay`, still play where they drive a sound chip of
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their own: on the Amiga, the ST, DOS, and the X68000.
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=== Constants
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[cols="3,1,4", options="header"]
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|===
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|Name |Value |Meaning
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|`JL_AUDIO_SFX_SLOTS` |5 |Sound effect slots, 0..4.
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|`JL_AUDIO_VOICES` |3 |PSG-style tone voices, 0..2.
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|`JL_SFX_RAW_SIGNED8` |0 |Raw stream format: `int8_t` PCM.
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|`JL_SFX_RAW_UNSIGNED8_NOZERO` |1 |Raw stream format: `uint8_t` biased 0x80,
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and 0x00 is forbidden (it is the DOC stop byte).
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|===
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[TIP]
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====
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Prefer *slot 4* for game sound effects when music is playing. The IIgs plays
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tone voices 0..2 on sound effect slots 0..2 and the noise on slot 3: an effect
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and a voice on the same slot cut each other off, and a voice still being held
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takes its slot back at the next `jlAudioFrameTick`. On the Amiga effects, the
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module, the voices, and the noise share Paula's four channels, so an effect can
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take a channel a voice is using. On the other ports the slots are independent
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of the voice layer.
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====
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=== jlAudioFrameTick
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[source,c]
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----
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void jlAudioFrameTick(void);
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----
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Hooks the engine into your game loop. Every port does its sound work here: DOS,
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the ST, the X68000, DVX, and the hosted ports mix or refill their sound buffers
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in it, so without it modules and effects stop or repeat; the IIgs and Amiga
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feed each streaming sound effect its next chunk, notice a module's end, and
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(on the IIgs) keep held notes sounding; and on every port it advances
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`jlMusicPlay`.
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Call it once per frame, unconditionally.
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*Parameters:* none. *Returns:* nothing.
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=== jlAudioPlayMod
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[source,c]
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----
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void jlAudioPlayMod(const uint8_t *data, uint32_t length, bool loop);
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----
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Begins module playback. If a module is already playing it is replaced.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`data` |`const uint8_t *` |Platform-native module blob: `.mod` on every port
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but the IIgs (an `.amod`, with its end marker, plays on the Amiga too), `.ntp`
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on the IIgs. The asset pipeline produces the right form.
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|`length` |`uint32_t` |Blob size in bytes.
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|`loop` |`bool` |`true` plays forever.
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|===
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*Returns:* nothing.
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[NOTE]
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====
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`loop = false` plays the song once and stops it. The IIgs's replayer has a
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play-once mode; the ports that mix modules in software stop where the song
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comes back to a row it has played (its end, or a jump back), at an `F00`, or
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at the Amiga's `E8F` stop marker; and the Amiga adds that marker as it copies
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the module to chip RAM, sending the song's jumps back to it
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(<<_music_protracker_modules>>). A module with no room for one, all 128 song
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positions or all 128 patterns in use, loops there anyway, and so does one
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whose jump back sits in a pattern it also plays where that jump goes
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forward.
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====
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=== jlAudioStopMod
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[source,c]
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----
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void jlAudioStopMod(void);
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----
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Stops the current module and resets the playhead, so the next `jlAudioPlayMod`
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starts from the top.
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*Parameters:* none. *Returns:* nothing.
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=== jlAudioIsPlayingMod
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[source,c]
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----
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bool jlAudioIsPlayingMod(void);
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----
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*Parameters:* none.
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*Returns:* `true` while a module is producing output. `false` after a stop,
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once a song played with `loop = false` has ended, before the first play, and on
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platforms where audio init failed.
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=== jlAudioPlaySfx
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[source,c]
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----
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void jlAudioPlaySfx(uint8_t slot, const uint8_t *sample,
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uint32_t length, uint16_t rateHz);
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----
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Triggers a one-shot digital sound effect. If the slot is already playing, the
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new sample replaces it.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`slot` |`uint8_t` |Slot 0..`JL_AUDIO_SFX_SLOTS`-1. Prefer 4 alongside music.
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|`sample` |`const uint8_t *` |Raw signed 8-bit PCM.
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|`length` |`uint32_t` |Sample count in bytes.
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|`rateHz` |`uint16_t` |The rate the sample was recorded at; the engine
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re-pitches to its own output rate.
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|===
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*Returns:* nothing.
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Most ports read the sample where it is while it plays, so keep it valid and
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unchanged until it has finished or the slot has been stopped. The IIgs also
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remembers the last sample each slot played by its address, length, and rate,
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and plays its own copy when they match: changed bytes at the same address,
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length, and rate are not heard there.
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[NOTE]
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====
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The full -128..127 range is accepted everywhere, but the IIgs plays -128 as
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-127: its DOC treats the corresponding byte as a wave-end marker and would halt
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the voice. One level in 256, inaudible in practice.
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====
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=== jlAudioStreamFillT
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[source,c]
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----
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typedef uint32_t (*jlAudioStreamFillT)(void *ctx, int8_t *dst, uint32_t count);
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----
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Stream refill callback. Write up to `count` signed 8-bit samples to `dst` and
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return how many you wrote. Returning 0 signals end of stream and the slot
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deactivates.
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[WARNING]
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====
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On every port it is called in program time, from the call that starts the
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stream and then from `jlAudioFrameTick` (on DVX, also while the desktop runs).
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It must not block, and it should be quick: it runs inside those calls.
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====
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=== jlAudioPlaySfxStream
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[source,c]
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----
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void jlAudioPlaySfxStream(uint8_t slot, jlAudioStreamFillT fill,
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void *ctx, uint16_t rateHz);
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----
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Plays a streaming sound effect, pulling samples from your callback as the
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slot's prefetch buffer drains. Sound effects can therefore be arbitrarily long
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with no caller-side allocation.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`slot` |`uint8_t` |Slot 0..4. Replaces whatever is playing there.
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|`fill` |`jlAudioStreamFillT` |Refill callback.
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|`ctx` |`void *` |Opaque pointer handed back to the callback.
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|`rateHz` |`uint16_t` |Rate your callback produces; the engine resamples with
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linear interpolation.
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|===
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*Returns:* nothing.
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[IMPORTANT]
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====
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Every port feeds streams from `jlAudioFrameTick`, so *you must be calling
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`jlAudioFrameTick` every frame* or the stream stops. On the IIgs and Amiga the
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engine plays one chunk at a time (7 KB on the IIgs, 4 KB on the Amiga) and
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fires the next from it, so a chunk seam on those ports can carry up to one
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frame of jitter.
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====
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=== jlAudioSfxRawFormat / jlAudioPlaySfxStreamRaw
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[source,c]
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----
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uint8_t jlAudioSfxRawFormat(void);
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void jlAudioPlaySfxStreamRaw(uint8_t slot, jlAudioStreamFillT fill,
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void *ctx, uint16_t rateHz);
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----
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`jlAudioSfxRawFormat` returns this port's raw stream format, either
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`JL_SFX_RAW_SIGNED8` or `JL_SFX_RAW_UNSIGNED8_NOZERO`.
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`jlAudioPlaySfxStreamRaw` is `jlAudioPlaySfxStream` except your callback
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delivers bytes *already in that format*, so the port skips its per-byte
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conversion of every chunk. On the IIgs that conversion costs about 7
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microseconds a byte, some 50 ms for each 7 KB chunk. Every other port's raw
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format is signed PCM, so there this is simply the plain call (DVX still flips
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each byte for its sound library).
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If your producer cannot make the port's format, use `jlAudioPlaySfxStream`.
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*Parameters:* as `jlAudioPlaySfxStream`. *Returns:* nothing.
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=== jlAudioSetPan
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[source,c]
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----
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typedef enum {
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JL_AUDIO_PAN_LEFT = 0, JL_AUDIO_PAN_CENTER, JL_AUDIO_PAN_RIGHT, JL_AUDIO_PAN_COUNT
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} jlAudioPanE;
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void jlAudioSetPan(uint8_t slot, jlAudioPanE pan);
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----
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Places a sound effect slot in the stereo field. Slots start centred, and the
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setting sticks to the *slot*, surviving retriggers -- so set it once for a
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sound that should come from one side.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`slot` |`uint8_t` |Slot 0..4.
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|`pan` |`jlAudioPanE` |Placement. Out-of-range values are ignored.
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|===
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*Returns:* nothing.
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What each port can actually do:
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[cols="1,4", options="header"]
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|===
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|Platform |Behaviour
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|IIgs |All three. The DOC pans per oscillator, so a centred sound plays on two
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oscillators, one per side. A stock IIgs sums to mono, so this shows up only on
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a stereo card or an emulator.
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|Amiga |Left and right by choosing the Paula channel side; a Paula channel plays
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on one side only. A centred sound plays on a free channel each side when both
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sides have one, so it reaches both ears; otherwise on the one channel
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PTPlayer picks.
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|X68000 |Ignored. Everything mixes into one ADPCM stream, so panning would move
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all audio at once.
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|DOS, ST, STe |Ignored. Output is mono.
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|DVX |All three, through DVX's stereo mixer (on a stereo card).
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|SDL3, web, Win32, PSP, Haiku, BeOS |All three: the port mixes in stereo.
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|Win16 |Ignored. Output is mono.
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|===
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=== jlAudioStopSfx
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[source,c]
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----
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void jlAudioStopSfx(uint8_t slot);
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----
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`slot` |`uint8_t` |Slot to silence. A no-op if already idle.
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|===
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*Returns:* nothing.
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=== jlAudioTone
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[source,c]
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----
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void jlAudioTone(uint16_t freqHz);
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----
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A single tone that plays until the next call: `jlAudioVoice(0, freqHz, 0)`,
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tone voice 0 at full volume, on every port. Designed for AGI-era music where
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the engine programs a divisor and lets the chip play, so CPU cost during
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playback is zero. A program that mixes it with `jlAudioVoice` or `jlMusicPlay`
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shares voice 0 with them. On DOS without an OPL2 (AdLib) chip, voice 0, and so
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this tone, is the PC speaker.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`freqHz` |`uint16_t` |Frequency in Hz. 0 silences the generator.
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|===
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*Returns:* nothing. Silent wherever voice 0 is (see `jlAudioVoice`).
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=== jlAudioVoice
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[source,c]
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----
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void jlAudioVoice(uint8_t voice, uint16_t freqHz, uint8_t atten);
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----
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Three-voice PSG-style polyphonic tone generator.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`voice` |`uint8_t` |Voice 0, 1, or 2.
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|`freqHz` |`uint16_t` |Frequency in Hz. 0 silences this voice.
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|`atten` |`uint8_t` |AGI / SN76489-style 4-bit attenuation: 0 loudest,
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15 silent, 2 dB per step as near as the chip comes (the ST's YM2149 has
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sixteen levels about 3.5 dB apart, so a step there is within 1.6 dB).
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|===
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*Returns:* nothing.
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Mapping to hardware: DOS uses AdLib OPL2 melodic channels 0..2 (with no OPL2,
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voice 0 is the PC speaker and voices 1 and 2 are silent); the ST uses YM2149
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channels A, B, and C (on the plain ST voice 0 is silent while digital sound
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plays); the Amiga uses Paula channels 0..2 looping a two-byte square sample;
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the IIgs uses Ensoniq DOC oscillators playing a resident square on sound
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effect slots 0..2; the X68000 uses YM2151 channels 0..2, one operator each,
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so its tones are sine waves; DVX plays square tones of its sound library,
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which puts them on the FM chip when there is a free voice and mixes them
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otherwise; the hosted ports mix square waves in software. The OPL2's waves
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are not square either.
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[IMPORTANT]
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====
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A note sounds until the next call for that voice. The IIgs plays each note as
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a sample a fraction of a second long and restarts the notes being held from
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`jlAudioFrameTick`, so call that every frame, as every program should; a frame
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much longer than 80 ms can leave a gap in a held note there.
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====
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=== jlAudioNoise
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[source,c]
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----
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void jlAudioNoise(uint8_t pitch, uint8_t atten);
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----
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Noise and percussion generator -- the fourth logical voice of the tracker
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layer.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`pitch` |`uint8_t` |0..31 in YM2149 noise-period style: 0 is the brightest
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hiss (hats), 31 the lowest rumble (toms).
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|`atten` |`uint8_t` |As `jlAudioVoice`. 15 or above silences.
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|===
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*Returns:* nothing.
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The noise runs at 125000 / `pitch` Hz (`pitch` 0 as 1), the YM2149's rate, on
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every port as far as its chip goes. Mapping: the ST uses the YM2149 noise
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generator mixed onto channel C; the X68000 the YM2151's noise, at the same
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rates exactly; the Amiga Paula channel 3 looping an LFSR noise sample, whose
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fastest rate, 28.6 kHz, pitches 0 to 4 all play at; the IIgs a resident noise
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sample on slot 3, up to 26 kHz, likewise for pitches 0 to 4; DVX a noise tone
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of its sound library; and the hosted ports mix the YM2149's own noise in
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software (its 17-bit generator), so it sounds as on the ST. DOS uses the OPL2
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rhythm-mode snare, leaving the three tone channels untouched: a tuned drum,
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not free-running noise, whose pitch spreads over the snare's range rather than
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following the YM2149's rate.
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[WARNING]
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====
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On the ST, noise shares channel C's volume register with tone voice 2. Author
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noise hits and voice-2 notes so they do not sound simultaneously; `songbake`
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warns when they overlap.
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====
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=== jlMusicPlay
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[source,c]
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----
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bool jlMusicPlay(const uint8_t *data, uint32_t length, bool loop);
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----
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Plays a JYM1 event stream baked by `songbake` through the tone and noise layer.
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One authored song plays on every port at register-write cost. Because there
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is no CPU mixing, this is fully viable on the ST and cheap on DOS, which
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`.MOD` playback is not.
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Playback is pumped by `jlAudioFrameTick` and paced by `jlMillisElapsed`, so
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tempo holds across 50, 60, and 70 Hz ports.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`data` |`const uint8_t *` |JYM1 stream. *Read in place* -- it must stay valid
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until `jlMusicStop` or song end.
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|`length` |`uint32_t` |Stream size in bytes.
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|`loop` |`bool` |`true` restarts at the authored loop point, or the top if the
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song has none. `false` silences the voices at song end.
|
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|===
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*Returns:* `true` on success; `false` on a malformed stream, in which case
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nothing plays. With `jlConfigT.noAudio` the song runs silently, its time and
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its end as usual.
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=== jlMusicStop
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[source,c]
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----
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void jlMusicStop(void);
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----
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Stops tracker playback and silences tones and noise. The playhead is discarded;
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use `jlMusicPause` to keep it. Safe when nothing is playing.
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*Parameters:* none. *Returns:* nothing.
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=== jlMusicIsPlaying
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[source,c]
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----
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bool jlMusicIsPlaying(void);
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----
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*Parameters:* none.
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*Returns:* `true` while a stream is loaded and active. Paused counts as active;
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stopped or finished does not.
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=== jlMusicPause / jlMusicResume
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[source,c]
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----
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void jlMusicPause(void);
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void jlMusicResume(void);
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----
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Pauses in place -- voices go silent, the playhead keeps its position -- and
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picks up where it left off. The current row restarts, and wall-clock time spent
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paused is not fast-forwarded through. Both are safe no-ops when there is no
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active song.
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*Parameters:* none. *Returns:* nothing.
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=== jlMusicSetAtten
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[source,c]
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----
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void jlMusicSetAtten(uint8_t atten);
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----
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|
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Global music attenuation, added to every authored voice and noise attenuation.
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Applies immediately to sounding voices and to everything played afterwards.
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Step it over successive frames for fades.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`atten` |`uint8_t` |0 plays as authored, 15 is silent.
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|===
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*Returns:* nothing.
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[NOTE]
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====
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`jlMusicPlay` does *not* reset this, so a fade-out carries into the next song
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unless you clear it.
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====
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=== jlAudioTickRegister
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|
[source,c]
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----
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typedef void (*jlAudioTickFnT)(void);
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bool jlAudioTickRegister(jlAudioTickFnT fn, uint16_t hz);
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----
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|
|
Registers a periodic callback for sound schedulers needing better than
|
|
frame-rate resolution. PSG-era music drivers use this to write register changes
|
|
at exact note boundaries: frame-rate scheduling batches several notes into one
|
|
frame, so the chip only hears the last write and short notes vanish.
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|
|
[cols="1,1,4", options="header"]
|
|
|===
|
|
|Parameter |Type |Description
|
|
|`fn` |`jlAudioTickFnT` |Callback, which may be fired from an interrupt. Pass
|
|
`NULL` to uninstall.
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|`hz` |`uint16_t` |Firings per second.
|
|
|===
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|
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|
*Returns:* `true` if installed. `false` when `hz` is 0, when audio is off or
|
|
did not start, or when the port cannot take the rate (above 1000 Hz on DVX, or
|
|
above the mixer's rate on the hosted ports). Uninstalling always returns
|
|
`true`.
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|
|
|
[WARNING]
|
|
====
|
|
`fn` may run in an interrupt: it does on DOS, the Amiga, the ST, and the
|
|
X68000. Keep it to memory reads and direct hardware register writes -- no
|
|
allocation, no `printf`, nothing blocking -- and share data with it through
|
|
`jlAudioCriticalEnter` and `jlAudioCriticalExit`.
|
|
====
|
|
|
|
On every port the calls average exactly `hz` a second; where they fall
|
|
differs. DOS, the Amiga, and the hosted ports place each one at its own time.
|
|
The ST and X68000 deliver them from the system's own timer, 200 and 100 times a
|
|
second, so the calls due between two of its ticks come together. The IIgs and
|
|
DVX deliver them in program time from `jlAudioFrameTick`, so a frame's calls
|
|
come together at it.
|
|
|
|
On DOS this reprograms PIT counter 0 and hooks INT 8, keeping the BIOS tick
|
|
counter advancing at the canonical 18.2 Hz through an accumulator so `time`
|
|
stays correct. `jlMillisElapsed` carries on from where it was when the tick
|
|
starts or stops; it never jumps back.
|
|
|
|
On the Amiga a `timer.device` request on the E-clock raises a software
|
|
interrupt at each tick. On the ST the tick rides TOS's 200 Hz Timer C
|
|
interrupt, and on the X68000 Human68k's 100 Hz Timer C interrupt.
|
|
|
|
On the IIgs `fn` runs in program time, at `jlAudioFrameTick`, as many times as
|
|
the display's beats since the last frame have made due, so the average is
|
|
exact whatever the program's frame rate.
|
|
|
|
On DVX a timer of DVX's (at most 1000 Hz) counts the ticks, and `fn` runs in
|
|
program time, once per counted tick, at the next `jlAudioFrameTick`: DVX's
|
|
sound library, which `jlAudioVoice` and the rest go through there, may not be
|
|
called from an interrupt. `fn` may therefore do anything, but what it does
|
|
lands on the frame, not between frames.
|
|
|
|
On the hosted ports the sound is mixed in program time, a few frames ahead,
|
|
and `fn` is called by the mixer between exactly the two samples where its tick
|
|
falls: in program time, so it may do anything, yet a note it starts begins at
|
|
the right place in the sound. `hz` may be anything up to the mixer's rate,
|
|
44100 (22050 on Win16).
|
|
|
|
=== jlAudioCriticalEnter / jlAudioCriticalExit
|
|
|
|
[source,c]
|
|
----
|
|
void jlAudioCriticalEnter(void);
|
|
void jlAudioCriticalExit(void);
|
|
----
|
|
|
|
Critical section against the tick interrupt. If you mutate state that the
|
|
registered tick callback reads, wrap the mutation in these so the interrupt
|
|
cannot observe a half-written value. On DOS, the Amiga, the ST, and the
|
|
X68000 a section holds every interrupt off, so keep it short. Sections nest:
|
|
only the outermost pair does anything, and its Exit puts back the interrupt
|
|
state its Enter found. On the IIgs, DVX, and the hosted ports, whose
|
|
callbacks run in program time, they do nothing, and need not.
|
|
|
|
*Parameters:* none. *Returns:* nothing.
|