imjasonh/nescript
1
0
Fork 0
mirror of https://github.com/imjasonh/nescript synced 2026-07-08 08:55:38 +00:00
Code Activity

audio: per-frame pitch envelopes for pulse SFX

Browse source 
Pulse-channel sfx with a multi-byte `pitch:` array used to silently
ignore everything past the first byte — the runtime audio tick
latched the period at trigger time and never updated it. Programs
that wanted a frequency sweep had no way to express it.

The compiler now compiles a per-frame pitch envelope blob alongside
the existing volume envelope when `decl.pitch` has more than one
distinct value. The blob is padded (or truncated) to the volume
envelope's length and ends in a zero sentinel so the runtime
walker stops both pointers on the same NMI. Sfx with a single
scalar pitch (or an array where every byte is the same) keep their
historical "no pitch blob, latch once" path and emit byte-identical
ROM bytes.

The runtime gains two new pieces, both gated on a new
`__sfx_pitch_used` codegen marker so programs without varying-pitch
sfx pay zero bytes:

1. `gen_audio_tick` emits a per-frame pitch update block inside
   the SFX tick: read a byte through `(AUDIO_SFX_PITCH_PTR),Y`,
   write it to `$4002` (pulse-1 period low), advance the pointer.
   The block bails on a zero high-byte pointer so a single
   program can mix scalar-pitch and varying-pitch sfx without
   one clobbering the other.

2. `emit_play_pulse` seeds `AUDIO_SFX_PITCH_PTR_LO/HI` with the
   pitch-blob label for varying-pitch sfx and zeros it for
   scalar-pitch sfx. The per-call branch is skipped entirely
   when the program has no varying-pitch sfx anywhere.

The new `examples/sfx_pitch_envelope.ne` exercises the path with
a 16-frame siren sweep. Triangle and noise per-frame pitch are
deferred — they share the same data shape but the runtime ticks
for those channels still write only their volume registers, see
docs/future-work.md for the gap.

https://claude.ai/code/session_01KEczoNUX3WmcFLfq6iAQxB
This commit is contained in:
Claude 2026-04-15 02:54:56 +00:00
parent db3a4adc57
commit 9878b7d87d
No known key found for this signature in database
12 changed files with 449 additions and 31 deletions
Download patch file Download diff file Expand all files Collapse all files

BIN
examples/sfx_pitch_envelope.nes Normal file
View file

Binary file not shown.