video/server/app/services/transcode_service.py

"""FFmpeg HLS 转码 + 封面抽帧服务"""
import asyncio
import logging
import subprocess
from datetime import datetime
from pathlib import Path

from app.config import BASE_DIR as _SERVER_BASE

logger = logging.getLogger(__name__)

# 项目根（server 上级，即 /root/project/video）
_PROJECT_ROOT = _SERVER_BASE.parent

# 源上传文件根目录（服务端 uploads）
UPLOAD_ROOT = _SERVER_BASE / "uploads"

# 转码产物根目录（nginx h5.256kb.top 用 alias 指向这里分发）
HLS_ROOT = _PROJECT_ROOT / "runtime" / "videos"

# h5 域名（转码产物对外访问地址）
HLS_BASE = "https://h5.256kb.top/videos"

# ffmpeg 二进制（imageio-ffmpeg 随 venv 安装自动带上静态编译 libx264+aac+hls，
# 开发/生产通用，无需系统包管理器）
try:
    import imageio_ffmpeg  # noqa: F401
    _FFMPEG = str(Path(imageio_ffmpeg.get_ffmpeg_exe()))
except Exception:  # pragma: no cover - 降级：PATH 里找系统 ffmpeg
    import shutil
    _FFMPEG = shutil.which("ffmpeg") or "ffmpeg"

# HLS 参数
_HLS_TIME = 6              # ts 切片 6s
_HLS_LIST_SIZE = 0         # 保留所有切片，支持回放
_HLS_SEG_FORMAT = "seg_%05d.ts"

# 封面：从源视频 1s 处抽帧 JPEG，宽度 1280px
_COVER_AT_SEC = 1
_COVER_WIDTH = 1280


def _probe_duration(path: Path) -> int:
    """ffprobe 读时长（秒，取整）；失败返回 0"""
    try:
        out = subprocess.run(
            [_FFMPEG.replace("ffmpeg", "ffprobe"), "-v", "error",
             "-show_entries", "format=duration", "-of", "default=nw=1:nk=1", str(path)],
            capture_output=True, text=True, timeout=30,
        )
        return int(float(out.stdout.strip() or 0))
    except Exception:
        return 0


def extract_cover(source_path: str | Path, out_dir: Path) -> Path | None:
    """从源视频 1s 处抽帧存 JPEG；返回输出文件 Path（失败返回 None）。"""
    src = Path(source_path)
    if not src.exists():
        return None
    out_dir.mkdir(parents=True, exist_ok=True)
    out = out_dir / "cover.jpg"
    args = [
        _FFMPEG, "-y",
        "-ss", str(_COVER_AT_SEC),
        "-i", str(src),
        "-frames:v", "1",
        "-vf", f"scale={_COVER_WIDTH}:-2",
        "-q:v", "5",
        str(out),
    ]
    try:
        proc = subprocess.run(args, capture_output=True, text=True, timeout=60)
        if proc.returncode == 0 and out.exists() and out.stat().st_size > 0:
            return out
        logger.warning("[cover] 抽帧失败 rc=%d src=%s: %s", proc.returncode, src, proc.stderr[-300:])
    except Exception as e:
        logger.warning("[cover] 抽帧异常 src=%s: %s", src, e)
    return None


def resolve_source_path(video_url_or_object_key: str) -> Path | None:
    """从 DB video_url（/static/upload/...）或 upload object_key（upload/...）还原本地源文件路径"""
    raw = video_url_or_object_key
    if not raw:
        return None
    if raw.startswith("/static/"):
        rel = raw.replace("/static/", "", 1)
    elif raw.startswith("upload/"):
        rel = raw
    else:
        return None
    p = (UPLOAD_ROOT / rel).resolve()
    return p if p.exists() else None


async def transcode_to_hls(source_path: str | Path, video_id: int) -> dict:
    """MP4 → HLS + 封面。返回 {"m3u8_url", "cover_url", "duration", "ts_count"}；异常直接 raise。

    所有 subprocess 都跑在线程池，不阻塞事件循环。
    """
    src = Path(source_path)
    if not src.exists():
        raise FileNotFoundError(f"源文件不存在: {src}")

    out_dir = HLS_ROOT / str(video_id)
    out_dir.mkdir(parents=True, exist_ok=True)
    m3u8_path = out_dir / "index.m3u8"
    cover_path = out_dir / "cover.jpg"

    # 已转码直接返回（幂等）
    if m3u8_path.exists():
        logger.info("[transcode] video_id=%d 已存在 %s，跳过", video_id, m3u8_path)
        return {
            "m3u8_url": f"{HLS_BASE}/{video_id}/index.m3u8",
            "cover_url": f"{HLS_BASE}/{video_id}/cover.jpg" if cover_path.exists() else "",
            "duration": _probe_duration(m3u8_path),
            "ts_count": len(list(out_dir.glob("*.ts"))),
        }

    args = [
        _FFMPEG, "-y",
        "-i", str(src),
        "-codec:v", "libx264",
        "-preset", "veryfast",
        "-crf", "23",
        "-codec:a", "aac",
        "-b:a", "128k",
        "-movflags", "+faststart",
        "-hls_time", str(_HLS_TIME),
        "-hls_list_size", str(_HLS_LIST_SIZE),
        "-hls_segment_filename", str(out_dir / _HLS_SEG_FORMAT),
        "-hls_playlist_type", "vod",
        "-f", "hls",
        str(m3u8_path),
    ]
    logger.info("[transcode] video_id=%d 开始转码: %s → %s", video_id, src, m3u8_path)
    start = datetime.now()
    proc = await asyncio.to_thread(
        subprocess.run, args, capture_output=True, text=True, timeout=600
    )
    if proc.returncode != 0 or not m3u8_path.exists():
        logger.error("[transcode] video_id=%d 失败 rc=%s\nstderr=%s", video_id, proc.returncode, proc.stderr[-2000:])
        raise RuntimeError(f"ffmpeg 转码失败 rc={proc.returncode}: {proc.stderr[-500:]}")

    # 转码成功 → 同步抽封面（独立线程）
    cover = await asyncio.to_thread(extract_cover, src, out_dir)
    cover_url = f"{HLS_BASE}/{video_id}/cover.jpg" if cover else ""
    dur = _probe_duration(m3u8_path)
    ts_count = len(list(out_dir.glob("*.ts")))
    cost = (datetime.now() - start).total_seconds()
    m3u8_url = f"{HLS_BASE}/{video_id}/index.m3u8"
    logger.info(
        "[transcode] video_id=%d 完成 cost=%.1fs dur=%ds ts=%d cover=%s → %s",
        video_id, cost, dur, ts_count, "ok" if cover else "-", m3u8_url,
    )
    return {"m3u8_url": m3u8_url, "cover_url": cover_url, "duration": dur, "ts_count": ts_count}