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"""Audio assembly: combining chunks, speed adjustment, cleanup."""
import logging
import shutil
import subprocess
import traceback
from pathlib import Path
from typing import Dict, List, Optional
from . import config
logger = logging.getLogger(__name__)
def atempo_filters(speed: float) -> str:
"""Return a comma-joined ffmpeg ``atempo`` filter chain for ``speed``.
``atempo`` accepts 0.5..2.0 per filter; values outside that range are
handled by chaining multiple filters. Returns "" when ``speed`` is 1.0.
"""
if speed <= 0:
raise ValueError(f"Speed must be a positive number, got {speed}")
if abs(speed - 1.0) < 1e-6:
return ""
remaining = float(speed)
chain = []
while remaining > 2.0:
chain.append("atempo=2.0")
remaining /= 2.0
while remaining < 0.5:
chain.append("atempo=0.5")
remaining /= 0.5
chain.append(f"atempo={remaining:g}")
return ",".join(chain)
def speed_export_params(speed: float) -> List[str]:
"""Return ffmpeg filter args for pitch-preserving speed adjustment."""
filters = atempo_filters(speed)
if not filters:
return []
return ["-filter:a", filters]
def _concat_escape(path: str) -> str:
"""Escape a path for use inside single quotes in an ffmpeg concat list."""
return path.replace("'", "'\\''")
def combine_chunks(total_chunks: int, output_path: Path,
results: Optional[Dict[int, bool]] = None, speed: float = 1.0) -> bool:
"""Combine audio chunks into the final audiobook using ffmpeg's concat demuxer.
``results`` maps chunk numbers to success flags; failed chunks are
skipped. When ``speed`` differs from 1.0, an additional speed-adjusted
copy is written next to the normal-speed file. Chunks are streamed by
ffmpeg, so the whole book is never held in memory.
"""
if shutil.which("ffmpeg") is None:
logger.error("ffmpeg is required to combine audio chunks (install ffmpeg)")
return False
chunk_files = []
missing_chunks = []
for i in range(1, total_chunks + 1):
# Skip chunks that failed if we have results tracking
if results is not None and not results.get(i, False):
missing_chunks.append(i)
continue
matches = sorted(config.CHUNKS_FOLDER.glob(f"chunk_{i:04d}.*"))
if matches:
chunk_files.append(matches[0])
else:
missing_chunks.append(i)
if not chunk_files:
logger.error("No valid chunks found")
return False
if missing_chunks:
logger.warning("Missing chunks: %s", missing_chunks)
concat_list = config.CHUNKS_FOLDER / "_concat_list.txt"
try:
with open(concat_list, "w", encoding="utf-8") as list_file:
for chunk_file in chunk_files:
list_file.write(f"file '{_concat_escape(str(chunk_file))}'\n")
filters = atempo_filters(speed)
if filters:
speed_path = output_path.with_name(f"{output_path.stem}_{speed:g}{output_path.suffix}")
cmd = [
"ffmpeg", "-y", "-f", "concat", "-safe", "0", "-i", str(concat_list),
"-filter_complex",
f"[0:a]split=2[base][spd];[spd]{filters}[spdout]",
"-map", "[base]", "-b:a", config.AUDIO_BITRATE, str(output_path),
"-map", "[spdout]", "-b:a", config.AUDIO_BITRATE, str(speed_path),
]
else:
speed_path = None
cmd = [
"ffmpeg", "-y", "-f", "concat", "-safe", "0", "-i", str(concat_list),
"-b:a", config.AUDIO_BITRATE, str(output_path),
]
proc = subprocess.run(cmd, capture_output=True, text=True)
if proc.returncode != 0:
logger.error("ffmpeg failed: %s", proc.stderr[-2000:])
return False
logger.info("Audiobook saved: %s (%d/%d chunks)", output_path, len(chunk_files), total_chunks)
print(f"[INFO] Saved audiobook: {output_path.name} ({len(chunk_files)}/{total_chunks} chunks)")
if filters:
logger.info("Saved speed-adjusted audiobook (%gx): %s", speed, speed_path)
print(f"[INFO] Saved speed-adjusted audiobook: {speed_path.name} ({speed:g}x)")
if missing_chunks:
print(f"[WARNING] Missing chunks: {missing_chunks}")
return True
except FileNotFoundError:
logger.error("ffmpeg not found on PATH (install ffmpeg and try again)")
return False
except Exception as exc:
logger.error("Failed to combine chunks: %s", exc)
logger.error(traceback.format_exc())
return False
finally:
try:
concat_list.unlink(missing_ok=True)
except OSError:
pass
def cleanup_chunks() -> None:
"""Remove temporary chunk files from the scratch folder."""
try:
chunk_count = 0
for chunk_file in config.CHUNKS_FOLDER.glob("chunk_*"):
try:
if chunk_file.is_file():
chunk_file.unlink()
chunk_count += 1
except Exception as exc:
logger.warning("Failed to delete %s: %s", chunk_file, exc)
if chunk_count > 0:
logger.info("Cleaned up %d chunk files", chunk_count)
print(f"[INFO] Cleaned up {chunk_count} chunk files")
except Exception as exc:
logger.warning("Cleanup failed: %s", exc)
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