claudetools/projects/radio-show/audio-processor/src/audio_editor.py

"""Stage 4 & 5: Commercial removal and segment splitting using ffmpeg."""

import subprocess
import json
from dataclasses import dataclass
from pathlib import Path

from rich.console import Console
from rich.progress import Progress

from .segment_detector import SegmentType, DetectedSegment

console = Console()


@dataclass
class Chapter:
    title: str
    start: float
    end: float


def remove_commercials(audio_path: Path, segments: list[DetectedSegment],
                       output_path: Path, crossfade_ms: int = 500,
                       bitrate: str = "192k", normalize: bool = True):
    """Stitch show segments together, removing commercials."""
    show_segments = [s for s in segments
                     if s.segment_type in (SegmentType.SHOW_CONTENT,
                                           SegmentType.SHOW_ELEMENT)]

    if not show_segments:
        console.print("[red]No show segments found![/red]")
        return

    console.print(f"[bold]Removing commercials:[/bold] {len(segments)} segments "
                  f"-> {len(show_segments)} show segments")

    output_path.parent.mkdir(parents=True, exist_ok=True)
    temp_dir = output_path.parent / ".temp_segments"
    temp_dir.mkdir(exist_ok=True)

    try:
        # Extract each show segment
        segment_files = []
        with Progress(console=console) as progress:
            task = progress.add_task("Extracting segments...",
                                     total=len(show_segments))

            for i, seg in enumerate(show_segments):
                temp_file = temp_dir / f"seg_{i:04d}.mp3"
                _extract_segment(audio_path, seg.start, seg.end,
                                temp_file, bitrate)
                segment_files.append(temp_file)
                progress.update(task, advance=1)

        # Create concat file for ffmpeg
        concat_file = temp_dir / "concat.txt"
        with open(concat_file, "w") as f:
            for sf in segment_files:
                f.write(f"file '{sf}'\n")

        # Concatenate with crossfade
        cmd = [
            "ffmpeg", "-y", "-f", "concat", "-safe", "0",
            "-i", str(concat_file),
            "-b:a", bitrate,
        ]

        if normalize:
            # EBU R128 loudness normalization
            cmd.extend([
                "-af", "loudnorm=I=-16:TP=-1.5:LRA=11",
            ])

        cmd.append(str(output_path))

        subprocess.run(cmd, capture_output=True, check=True, timeout=600)

        # Get output duration
        duration = _get_duration(output_path)
        console.print(f"[green]Clean episode saved: {output_path.name} "
                      f"({duration / 60:.1f} min)[/green]")

    finally:
        # Cleanup temp files
        import shutil
        shutil.rmtree(temp_dir, ignore_errors=True)


def split_segments(audio_path: Path, segments: list[DetectedSegment],
                   output_dir: Path, bitrate: str = "192k"):
    """Export individual show segments as separate MP3 files."""
    show_segments = [s for s in segments
                     if s.segment_type in (SegmentType.SHOW_CONTENT,
                                           SegmentType.SHOW_ELEMENT)]

    output_dir.mkdir(parents=True, exist_ok=True)
    console.print(f"[bold]Splitting into {len(show_segments)} segments[/bold]")

    exported = []
    for i, seg in enumerate(show_segments):
        slug = _slugify(seg.label) if seg.label else f"segment-{i:02d}"
        filename = f"{i:02d}-{slug}.mp3"
        output_file = output_dir / filename

        _extract_segment(audio_path, seg.start, seg.end, output_file, bitrate,
                        fade_in_ms=200, fade_out_ms=500)

        duration = seg.duration
        console.print(f"  [green]{filename}[/green] ({duration:.0f}s)")
        exported.append({
            "file": filename,
            "label": seg.label,
            "start": seg.start,
            "end": seg.end,
            "duration": duration,
        })

    # Save manifest
    with open(output_dir / "segments.json", "w") as f:
        json.dump(exported, f, indent=2)

    return exported


def generate_chapters(segments: list[DetectedSegment],
                      output_path: Path) -> list[Chapter]:
    """Generate chapter markers from show segments."""
    show_segments = [s for s in segments
                     if s.segment_type in (SegmentType.SHOW_CONTENT,
                                           SegmentType.SHOW_ELEMENT)]

    chapters = []
    cumulative_time = 0.0

    for seg in show_segments:
        chapters.append(Chapter(
            title=seg.label or f"Segment",
            start=cumulative_time,
            end=cumulative_time + seg.duration,
        ))
        cumulative_time += seg.duration

    output_path.parent.mkdir(parents=True, exist_ok=True)
    with open(output_path, "w") as f:
        json.dump(
            [{"title": c.title, "start": c.start, "end": c.end}
             for c in chapters],
            f, indent=2,
        )

    console.print(f"[green]Chapter markers saved: {len(chapters)} chapters[/green]")
    return chapters


def _extract_segment(audio_path: Path, start: float, end: float,
                     output_path: Path, bitrate: str = "192k",
                     fade_in_ms: int = 0, fade_out_ms: int = 0):
    """Extract a segment from an audio file using ffmpeg."""
    duration = end - start
    cmd = [
        "ffmpeg", "-y",
        "-ss", str(start),
        "-t", str(duration),
        "-i", str(audio_path),
        "-b:a", bitrate,
    ]

    filters = []
    if fade_in_ms > 0:
        filters.append(f"afade=t=in:d={fade_in_ms / 1000}")
    if fade_out_ms > 0:
        filters.append(f"afade=t=out:st={duration - fade_out_ms / 1000}:d={fade_out_ms / 1000}")

    if filters:
        cmd.extend(["-af", ",".join(filters)])

    cmd.append(str(output_path))
    subprocess.run(cmd, capture_output=True, check=True, timeout=120)


def _get_duration(audio_path: Path) -> float:
    """Get audio file duration in seconds."""
    result = subprocess.run(
        ["ffprobe", "-v", "quiet", "-show_entries", "format=duration",
         "-of", "csv=p=0", str(audio_path)],
        capture_output=True, text=True,
    )
    return float(result.stdout.strip())


def _slugify(text: str) -> str:
    """Convert text to a filename-safe slug."""
    import re
    text = text.lower().strip()
    text = re.sub(r'[^\w\s-]', '', text)
    text = re.sub(r'[\s_]+', '-', text)
    text = re.sub(r'-+', '-', text)
    return text[:50].strip('-')