preprocess/tools/midi_parser.py

"""
SoulX-Singer MIDI <-> metadata converter.

Converts between SoulX-Singer-style metadata JSON (with note_text, note_dur,
note_pitch, note_type per segment) and standard MIDI files. Uses an internal
Note dataclass (start_s, note_dur, note_text, note_pitch, note_type) as the
intermediate representation.
"""
import os
import json
import shutil
from dataclasses import dataclass
from typing import Any, List, Tuple, Union

import librosa
import mido
from soundfile import write

from .f0_extraction import F0Extractor
from .g2p import g2p_transform


# Audio, MIDI and segmentation constants
SAMPLE_RATE = 44100             # Audio sample rate for any wav cuts during midi2meta
MIDI_TICKS_PER_BEAT = 500       # The number of MIDI ticks per beat; affects the time resolution of MIDI output and conversion accuracy.
MIDI_TEMPO = 500000             # Microseconds per beat (120 BPM)
MIDI_TIME_SIGNATURE = (4, 4)    # Default time signature; not critical for conversion but included in MIDI output.
MIDI_VELOCITY = 64              # Default velocity for note_on events; not critical for conversion but required for MIDI format.
END_EXTENSION_SEC = 0.4         # Extend each segment end by this much silence (sec) to give the model more context
MAX_GAP_SEC = 2.0               # Gap threshold to split segments in midi2meta (sec)
MAX_SEGMENT_DUR_SUM_SEC = 60.0  # Max total duration sum of notes in a single metadata segment before splitting into multiple segments (sec)
SILENCE_THRESHOLD_SEC = 0.2     # Threshold to insert explicit <SP> note for long silences between notes in midi2notes (sec)


@dataclass
class Note:
    """Single note: text, duration (seconds), pitch (MIDI), type. start_s is absolute start time in seconds (for ordering / MIDI)."""
    start_s: float
    note_dur: float
    note_text: str
    note_pitch: int
    note_type: int

    @property
    def end_s(self) -> float:
        return self.start_s + self.note_dur


def _seconds_to_ticks(seconds: float, ticks_per_beat: int, tempo: int) -> int:
    """Convert seconds to MIDI ticks based on tempo and ticks per beat."""
    return int(round(seconds * ticks_per_beat * 1_000_000 / tempo))


def _append_segment_to_meta(
    meta_data: List[dict],
    meta_path_str: str,
    cut_wavs_output_dir: str | None,
    vocal_file: str | None,
    language: str,
    audio_data: Any | None,
    pitch_extractor: F0Extractor | None,
    note_start: List[float],
    note_end: List[float],
    note_text: List[Any],
    note_pitch: List[Any],
    note_type: List[Any],
    note_dur: List[float],
) -> None:
    """Helper function for midi2meta to append the current segment (accumulated in note_*) to meta_data list, with optional wav cut and pitch extraction."""
    if not all((note_start, note_end, note_text, note_pitch, note_type, note_dur)):
        return

    base_name = os.path.splitext(os.path.basename(meta_path_str))[0]
    item_name = f"{base_name}_{len(meta_data)}"
    wav_fn = None
    if cut_wavs_output_dir and vocal_file and audio_data is not None:
        wav_fn = os.path.join(cut_wavs_output_dir, f"{item_name}.wav")
        end_pad = int(END_EXTENSION_SEC * SAMPLE_RATE)
        start_sample = max(0, int(note_start[0] * SAMPLE_RATE))
        end_sample = min(len(audio_data), int(note_end[-1] * SAMPLE_RATE) + end_pad)

        end_pad_dur = (end_sample / SAMPLE_RATE - note_end[-1]) if end_sample > int(note_end[-1] * SAMPLE_RATE) else 0.0
        if end_pad_dur > 0:
            note_dur = note_dur + [end_pad_dur]
            note_text = note_text + ["<SP>"]
            note_pitch = note_pitch + [0]
            note_type = note_type + [1]
        start_ms = int(start_sample / SAMPLE_RATE * 1000)
        end_ms = int(end_sample / SAMPLE_RATE * 1000)
        write(wav_fn, audio_data[start_sample:end_sample], SAMPLE_RATE)
    else:
        start_ms = int(note_start[0] * 1000)
        end_ms = int(note_end[-1] * 1000)

    if pitch_extractor is not None:
        if not wav_fn or not os.path.isfile(wav_fn):
            raise FileNotFoundError(f"Segment wav file not found: {wav_fn}")
        f0 = pitch_extractor.process(wav_fn)
    else:
        f0 = []

    note_text_list = list(note_text)
    note_pitch_list = list(note_pitch)
    note_type_list = list(note_type)
    note_dur_list = list(note_dur)

    meta_data.append(
        {
            "index": item_name,
            "language": language,
            "time": [start_ms, end_ms],
            "duration": " ".join(str(round(x, 2)) for x in note_dur_list),
            "text": " ".join(note_text_list),
            "phoneme": " ".join(g2p_transform(note_text_list, language)),
            "note_pitch": " ".join(str(x) for x in note_pitch_list),
            "note_type": " ".join(str(x) for x in note_type_list),
            "f0": " ".join(str(round(float(x), 1)) for x in f0),
        }
    )


def meta2notes(meta_path: str) -> List[Note]:
    """Parse SoulX-Singer metadata JSON into a flat list of Note (absolute start_s)."""
    with open(meta_path, "r", encoding="utf-8") as f:
        segments = json.load(f)
    if not isinstance(segments, list):
        raise ValueError(f"Metadata must be a list of segments, got {type(segments).__name__}")
    if not segments:
        raise ValueError("Metadata has no segments.")

    notes: List[Note] = []
    for seg in segments:
        offset_s = seg["time"][0] / 1000
        words = [str(x).replace("<AP>", "<SP>") for x in seg["text"].split()]
        word_durs = [float(x) for x in seg["duration"].split()]
        pitches = [int(x) for x in seg["note_pitch"].split()]
        types = [int(x) if words[i] != "<SP>" else 1 for i, x in enumerate(seg["note_type"].split())]
        if len(words) != len(word_durs) or len(word_durs) != len(pitches) or len(pitches) != len(types):
            raise ValueError(
                f"Length mismatch in segment {seg.get('item_name', '?')}: "
                "note_text, note_dur, note_pitch, note_type must have same length"
            )
        current_s = offset_s
        for text, dur, pitch, type_ in zip(words, word_durs, pitches, types):
            notes.append(
                Note(
                    start_s=current_s,
                    note_dur=float(dur),
                    note_text=str(text),
                    note_pitch=int(pitch),
                    note_type=int(type_),
                )
            )
            current_s += float(dur)
    return notes


def notes2meta(
    notes: List[Note],
    meta_path: str,
    vocal_file: str | None,
    language: str,
    pitch_extractor: F0Extractor | None,
) -> None:
    """Write SoulX-Singer metadata JSON from a list of Note (segmenting + wav cuts)."""
    meta_path_str = str(meta_path)

    cut_wavs_output_dir = None
    if vocal_file:
        cut_wavs_output_dir = os.path.join(os.path.dirname(vocal_file), "cut_wavs_tmp")
        os.makedirs(cut_wavs_output_dir, exist_ok=True)

    note_text: List[Any] = []
    note_pitch: List[Any] = []
    note_type: List[Any] = []
    note_dur: List[float] = []
    note_start: List[float] = []
    note_end: List[float] = []
    meta_data: List[dict] = []
    audio_data = None
    if vocal_file:
        audio_data, _ = librosa.load(vocal_file, sr=SAMPLE_RATE, mono=True)
    dur_sum = 0.0

    def flush_current_segment() -> None:
        nonlocal dur_sum
        _append_segment_to_meta(
            meta_data,
            meta_path_str,
            cut_wavs_output_dir,
            vocal_file,
            language,
            audio_data,
            pitch_extractor,
            note_start,
            note_end,
            note_text,
            note_pitch,
            note_type,
            note_dur,
        )
        note_text.clear()
        note_pitch.clear()
        note_type.clear()
        note_dur.clear()
        note_start.clear()
        note_end.clear()
        dur_sum = 0.0

    def append_note(start: float, end: float, text: str, pitch: int, type_: int) -> None:
        nonlocal dur_sum
        duration = end - start
        if duration <= 0:
            return

        if len(note_text) > 0 and text == "<SP>" and note_text[-1] == "<SP>":
            note_dur[-1] += duration
            note_end[-1] = end
        else:
            note_text.append(text)
            note_pitch.append(pitch)
            note_type.append(type_)
            note_dur.append(duration)
            note_start.append(start)
            note_end.append(end)
        dur_sum += duration

    for note in notes:
        start = float(note.start_s)
        end = float(note.end_s)
        text = note.note_text
        pitch = note.note_pitch
        type_ = note.note_type

        if text == "" or pitch == "" or type_ == "":
            append_note(start, end, "<SP>", 0, 1)
            continue
        
        # cut the segment when ends with a long <SP> note
        if (
            len(note_text) > 0
            and note_text[-1] == "<SP>"
            and note_dur[-1] > MAX_GAP_SEC
        ):
            note_text.pop()
            note_pitch.pop()
            note_type.pop()
            note_dur.pop()
            note_start.pop()
            note_end.pop()

            dur_sum = sum(note_dur)
            flush_current_segment()

        # cut the segment if adding the current note would exceed the max duration sum threshold
        if dur_sum + (end - start) > MAX_SEGMENT_DUR_SUM_SEC and len(note_text) > 0:
            flush_current_segment()

        append_note(start, end, text, int(pitch), int(type_))

    if note_text:
        flush_current_segment()

    with open(meta_path_str, "w", encoding="utf-8") as f:
        json.dump(meta_data, f, ensure_ascii=False, indent=2)

    if cut_wavs_output_dir:
        try:
            shutil.rmtree(cut_wavs_output_dir, ignore_errors=True)
        except Exception:
            pass


def notes2midi(
    notes: List[Note],
    midi_path: str,
) -> None:
    """Write MIDI file from a list of Note."""
    if not notes:
        raise ValueError("Empty note list.")

    events: List[Tuple[int, int, Union[mido.Message, mido.MetaMessage]]] = []
    for n in notes:
        start_s = n.start_s
        end_s = n.end_s
        if end_s <= start_s:
            continue

        start_ticks = _seconds_to_ticks(
            start_s, MIDI_TICKS_PER_BEAT, MIDI_TEMPO
        )
        end_ticks = _seconds_to_ticks(
            end_s, MIDI_TICKS_PER_BEAT, MIDI_TEMPO
        )
        if end_ticks <= start_ticks:
            end_ticks = start_ticks + 1

        lyric = n.note_text
        # Some DAWs store lyric text as latin1-compatible bytes; keep best-effort round-trip.
        try:
            lyric = lyric.encode("utf-8").decode("latin1")
        except (UnicodeEncodeError, UnicodeDecodeError):
            pass
        if n.note_type == 3:
            lyric = "-"

        events.append(
            (start_ticks, 1, mido.MetaMessage("lyrics", text=lyric, time=0))
        )
        events.append(
            (
                start_ticks,
                2,
                mido.Message(
                    "note_on",
                    note=n.note_pitch,
                    velocity=MIDI_VELOCITY,
                    time=0,
                ),
            )
        )
        events.append(
            (
                end_ticks,
                0,
                mido.Message("note_off", note=n.note_pitch, velocity=0, time=0),
            )
        )

    events.sort(key=lambda x: (x[0], x[1]))

    mid = mido.MidiFile(ticks_per_beat=MIDI_TICKS_PER_BEAT)
    track = mido.MidiTrack()
    mid.tracks.append(track)

    track.append(mido.MetaMessage("set_tempo", tempo=MIDI_TEMPO, time=0))
    track.append(
        mido.MetaMessage(
            "time_signature",
            numerator=MIDI_TIME_SIGNATURE[0],
            denominator=MIDI_TIME_SIGNATURE[1],
            time=0,
        )
    )

    last_tick = 0
    for tick, _, msg in events:
        msg.time = max(0, tick - last_tick)
        track.append(msg)
        last_tick = tick

    track.append(mido.MetaMessage("end_of_track", time=0))
    mid.save(midi_path)


def midi2notes(midi_path: str) -> List[Note]:
    """Parse MIDI file into a list of Note."""
    mid = mido.MidiFile(midi_path)
    ticks_per_beat = mid.ticks_per_beat
    tempo = 500000

    raw_notes: List[dict] = []
    lyrics: List[Tuple[int, str]] = []

    for track in mid.tracks:
        abs_ticks = 0
        active = {}
        for msg in track:
            abs_ticks += msg.time
            if msg.type == "set_tempo":
                tempo = msg.tempo
            elif msg.type == "lyrics":
                text = msg.text
                try:
                    text = text.encode("latin1").decode("utf-8")
                except Exception:
                    pass
                lyrics.append((abs_ticks, text))
            elif msg.type == "note_on":
                key = (msg.channel, msg.note)
                if msg.velocity > 0:
                    active[key] = (abs_ticks, msg.velocity)
                else:
                    if key in active:
                        start_ticks, vel = active.pop(key)
                        raw_notes.append(
                            {
                                "midi": msg.note,
                                "start_ticks": start_ticks,
                                "duration_ticks": abs_ticks - start_ticks,
                                "velocity": vel,
                                "lyric": "",
                            }
                        )
            elif msg.type == "note_off":
                key = (msg.channel, msg.note)
                if key in active:
                    start_ticks, vel = active.pop(key)
                    raw_notes.append(
                        {
                            "midi": msg.note,
                            "start_ticks": start_ticks,
                            "duration_ticks": abs_ticks - start_ticks,
                            "velocity": vel,
                            "lyric": "",
                        }
                    )

    if not raw_notes:
        raise ValueError("No notes found in MIDI file")

    for n in raw_notes:
        n["end_ticks"] = n["start_ticks"] + n["duration_ticks"]

    raw_notes.sort(key=lambda n: n["start_ticks"])
    lyrics.sort(key=lambda x: x[0])

    trimmed = []
    # Remove/trim overlaps so generated notes are strictly non-overlapping in tick domain.
    for note in raw_notes:
        while trimmed:
            prev = trimmed[-1]
            if note["start_ticks"] < prev["end_ticks"]:
                prev["end_ticks"] = note["start_ticks"]
                prev["duration_ticks"] = prev["end_ticks"] - prev["start_ticks"]
                if prev["duration_ticks"] <= 0:
                    trimmed.pop()
                    continue
            break
        trimmed.append(note)
    raw_notes = trimmed

    tolerance = ticks_per_beat // 100
    # Attach lyrics near note_on positions with a small tick tolerance.
    lyric_idx = 0
    for note in raw_notes:
        while lyric_idx < len(lyrics) and lyrics[lyric_idx][0] < note["start_ticks"] - tolerance:
            lyric_idx += 1
        if lyric_idx < len(lyrics):
            lyric_ticks, lyric_text = lyrics[lyric_idx]
            if abs(lyric_ticks - note["start_ticks"]) <= tolerance:
                note["lyric"] = lyric_text
                lyric_idx += 1

    def ticks_to_seconds(ticks: int) -> float:
        return (ticks / ticks_per_beat) * (tempo / 1_000_000)

    result: List[Note] = []
    prev_end_s = 0.0
    for idx, n in enumerate(raw_notes):
        start_s = ticks_to_seconds(n["start_ticks"])
        end_s = ticks_to_seconds(n["end_ticks"])
        if prev_end_s > start_s:
            start_s = prev_end_s
        dur_s = end_s - start_s
        if dur_s <= 0:
            continue

        lyric = n.get("lyric", "")
        # SoulX-Singer convention mapping from lyric token to note_type/text.
        if not lyric:
            note_type = 2
            text = "啦"
        elif lyric == "<SP>":
            note_type = 1
            text = "<SP>"
        elif lyric == "-":
            note_type = 3
            text = raw_notes[idx - 1].get("lyric", "-") if idx > 0 else "-"
        else:
            note_type = 2
            text = lyric

        if start_s - prev_end_s > SILENCE_THRESHOLD_SEC:
            # Explicitly represent long gaps as <SP> notes.
            result.append(
                Note(
                    start_s=prev_end_s,
                    note_dur=start_s - prev_end_s,
                    note_text="<SP>",
                    note_pitch=0,
                    note_type=1,
                )
            )
        else:
            if len(result) > 0:
                result[-1].note_dur = start_s - result[-1].start_s

        result.append(
            Note(
                start_s=start_s,
                note_dur=dur_s,
                note_text=text,
                note_pitch=n["midi"],
                note_type=note_type,
            )
        )
        prev_end_s = end_s

    return result


class MidiParser:
    def __init__(
        self,
        rmvpe_model_path: str,
        device: str = "cuda",
    ) -> None:
        self.rmvpe_model_path = rmvpe_model_path
        self.device = device
        self.pitch_extractor: F0Extractor | None = None

    def _get_pitch_extractor(self) -> F0Extractor:
        if self.pitch_extractor is None:
            self.pitch_extractor = F0Extractor(
                self.rmvpe_model_path,
                device=self.device,
                verbose=False,
            )
        return self.pitch_extractor

    def midi2meta(
        self,
        midi_path: str,
        meta_path: str,
        vocal_file: str | None = None,
        language: str = "Mandarin",
    ) -> None:
        meta_dir = os.path.dirname(meta_path)
        if meta_dir:
            os.makedirs(meta_dir, exist_ok=True)

        notes = midi2notes(midi_path)
        pitch_extractor = self._get_pitch_extractor() if vocal_file else None
        notes2meta(
            notes,
            meta_path,
            vocal_file,
            language,
            pitch_extractor=pitch_extractor,
        )
        print(f"Saved Meta to {meta_path}")

    def meta2midi(self, meta_path: str, midi_path: str) -> None:
        notes = meta2notes(meta_path)
        notes2midi(notes, midi_path)
        print(f"Saved MIDI to {midi_path}")

if __name__ == "__main__":
    import argparse

    parser = argparse.ArgumentParser(
        description="Convert SoulX-Singer metadata JSON <-> MIDI."
    )
    parser.add_argument("--meta", type=str, help="Path to metadata JSON")
    parser.add_argument("--midi", type=str, help="Path to MIDI file")
    parser.add_argument("--vocal", type=str, default=None, help="Path to vocal wav (optional for midi2meta)")
    parser.add_argument("--language", type=str, default="Mandarin", help="Lyric language for metadata phoneme conversion (default: Mandarin)")
    parser.add_argument(
        "--meta2midi",
        action="store_true",
        help="Convert meta -> midi (requires --meta and --midi)",
    )
    parser.add_argument(
        "--midi2meta",
        action="store_true",
        help="Convert midi -> meta (requires --midi and --meta; --vocal is optional)",
    )
    parser.add_argument(
        "--rmvpe_model_path",
        type=str,
        help="Path to RMVPE model",
        default="pretrained_models/SoulX-Singer-Preprocess/rmvpe/rmvpe.pt",
    )
    parser.add_argument(
        "--device",
        type=str,
        help="Device to use for RMVPE",
        default="cuda",
    )
    args = parser.parse_args()
    midi_parser = MidiParser(
        rmvpe_model_path=args.rmvpe_model_path,
        device=args.device,
    )

    if args.meta2midi:
        if not args.meta or not args.midi:
            parser.error("--meta2midi requires --meta and --midi")
        midi_parser.meta2midi(args.meta, args.midi)
    elif args.midi2meta:
        if not args.midi or not args.meta:
            parser.error(
                "--midi2meta requires --midi and --meta"
            )
        midi_parser.midi2meta(args.midi, args.meta, args.vocal, args.language)
    else:
        parser.print_help()