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resolving envelope ambiguity

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minjaesong
2026-05-06 17:10:13 +09:00
parent 0124b062d0
commit e64e335db3
7 changed files with 119 additions and 49 deletions
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18
it2taud.py
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@@ -571,9 +571,10 @@ def _parse_it_envelope(data: bytes, env_ptr: int, kind: str,
'filter' — IT -32..+32 → Taud 0..255 (0x80 = unity cutoff)
Word layout (terranmon.txt:2049+ / 2114+):
LOOP word: 0b 0000_0sss_ssXcb_eeeee (X = 'p'/'m' for pan/pf, 0 for vol)
LOOP word: 0b 00P0_0sss_ssXcb_eeeee (X = 'p'/'m' for pan/pf, 0 for vol)
SUSTAIN word: 0b 0000_0sss_ss00b_eeeee
bits 12..8 = start index, bits 4..0 = end index
bit 13 = P (envelope present; gates pan/pf evaluation in the engine)
bit 7 = p (pan: use default pan) / m (pf: pitch=0/filter=1) / 0 (vol)
bit 6 = c (envelope carry — placed in the LOOP word)
bit 5 = b (enable that region)
@@ -638,7 +639,10 @@ def _parse_it_envelope(data: bytes, env_ptr: int, kind: str,
# directly. Bits: 5=b enable, 6=c carry, 7=p (pan default-pan flag) /
# m (pf filter mode); 12..8=start, 4..0=end. SUSTAIN word never carries
# c/p/m — those live in the LOOP word.
loop_word = 0
# P (bit 13) marks the envelope as present in source, regardless of LOOP/
# SUSTAIN enable. We reach this point only when the IT envelope flag bit 0
# is set (handled at function top), so P is unconditionally set here.
loop_word = 0x2000 # P: envelope present
if has_env_loop and 0 <= it_lpb < 25 and 0 <= it_lpe < 25:
loop_word |= 0x0020 # b: enable LOOP
loop_word |= (it_lpb & 0x1F) << 8
@@ -1133,7 +1137,8 @@ def build_sample_inst_bin_it(samples_or_proxy: list,
# 256-byte instrument layout (terranmon.txt:2001+).
INST_STRIDE = 256
USE_ENV_BIT = 0x0020 # b — set whenever the engine should evaluate the envelope
USE_ENV_BIT = 0x0020 # b — LOOP wrap enable (legacy; engine still honours)
ENV_PRESENT_BIT = 0x2000 # P — envelope present in source (terranmon.txt byte 16/18/20 bit 5)
def _write_env(buf: bytearray, base: int, env_pts):
"""Write 25 (value, minifloat) pairs starting at `buf[base]`. Pads
@@ -1200,7 +1205,8 @@ def build_sample_inst_bin_it(samples_or_proxy: list,
# When the source has neither loop nor sustain on the volume envelope
# the engine still needs the b flag so the single-point unit envelope
# is evaluated — synthesise USE_ENV_BIT into the LOOP word as a fallback.
vol_env_loop = idata.get('vol_env_loop', USE_ENV_BIT)
# The P bit is informational for vol but set for consistency.
vol_env_loop = idata.get('vol_env_loop', USE_ENV_BIT | ENV_PRESENT_BIT)
vol_env_sus = idata.get('vol_env_sus', 0)
pan_env_loop = idata.get('pan_env_loop', 0)
pan_env_sus = idata.get('pan_env_sus', 0)
@@ -1236,8 +1242,10 @@ def build_sample_inst_bin_it(samples_or_proxy: list,
inst_bin[base + 22] = 0
# Force engine to use this single point — set the b bit on the LOOP
# word so the envelope is evaluated even though no wrap region exists.
# P is also set for consistency (vol-env presence is informational
# but converters mark it whenever they emit any node data).
cur_loop = struct.unpack_from('<H', inst_bin, base + 15)[0]
struct.pack_into('<H', inst_bin, base + 15, cur_loop | USE_ENV_BIT)
struct.pack_into('<H', inst_bin, base + 15, cur_loop | USE_ENV_BIT | ENV_PRESENT_BIT)
if pan_env:
_write_env(inst_bin, base + 71, pan_env)