siftlode/backend/app/downloads/edit.py
npeter83 b372d48ced feat(downloads): editor concat — multi-segment join (cut-list)
Editor v2 backend: an edit_spec can carry a 'segments' cut-list that concatenates the kept
ranges into ONE file (accurate=filter_complex trim+concat re-encode; fast=concat-demuxer
stream-copy with per-segment inpoint/outpoint). normalize/edit_sig/clip_duration/needs_reencode
handle segments; worker writes the concat list + runs build_concat_plan. Single-trim path (used by
'separate files' export) unchanged.
2026-07-04 03:15:45 +02:00

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"""Video editor (phase 2): per-user trim/crop derivatives via ffmpeg.
An edit derives a NEW per-user clip from an already-downloaded ready asset. It is never shared-
cached across users (the cache key embeds the user id), so it fully counts against the owner's
quota — but it still rides the same `MediaAsset`/`DownloadJob`/worker machinery as a download,
with the worker branching on the asset's `source_kind` to run ffmpeg instead of yt-dlp.
* trim, fast → stream copy (`-c copy`), instant, no quality loss, cuts SNAP to keyframes
(the in/out point can be off by a second or two)
* trim, accurate → re-encode (libx264 + aac), frame-accurate; cost scales with CLIP length
(the `-ss` seeks first), so a short clip is cheap even from a long source
* crop (± trim) → always re-encode (a filter can't be stream-copied), frame-accurate
`edit_spec = {trim?: {start_s, end_s}, crop?: {x, y, w, h}, accurate?: bool}`. `accurate` is the
per-edit user choice for a trim-only cut (ignored when a crop forces a re-encode anyway). `split`
is a frontend concept: the
UI fans a split out into N trim jobs, so there is one output file per job here.
Also builds the editor **filmstrip** — a single tiled sprite of the source video used as a visual
scrub track. Cached on the source asset's `storyboard_path` (reserved in phase 1) and reusable
for a player hover-preview later.
"""
import hashlib
import json
import logging
import math
import subprocess
from pathlib import Path
log = logging.getLogger("siftlode.edit")
class EditAborted(Exception):
"""Raised by run_ffmpeg when the job was paused/canceled mid-encode."""
# --- edit spec ------------------------------------------------------------------------------
def normalize_edit_spec(spec: dict | None) -> dict:
"""Canonicalize a raw edit spec: clamp/round trim, coerce crop to ints, drop empties.
The result is what gets hashed (so two equivalent specs share a cache row) and stored."""
spec = spec or {}
out: dict = {}
# Crop applies to both a single trim and a multi-segment join.
crop = spec.get("crop") or {}
if crop:
try:
c = {k: int(round(float(crop[k]))) for k in ("x", "y", "w", "h")}
except (KeyError, TypeError, ValueError):
c = None
if c and c["w"] > 0 and c["h"] > 0 and c["x"] >= 0 and c["y"] >= 0:
out["crop"] = c
# Multi-segment JOIN (cut-list → one concatenated file). Takes precedence over `trim`.
segs = spec.get("segments")
if isinstance(segs, list) and segs:
norm: list[dict] = []
for s in segs:
try:
st = max(0.0, float((s or {}).get("start_s") or 0.0))
end_raw = (s or {}).get("end_s")
if end_raw is None:
continue
en = float(end_raw)
except (TypeError, ValueError):
continue
if en > st:
norm.append({"start_s": round(st, 3), "end_s": round(en, 3)})
norm.sort(key=lambda x: x["start_s"])
if norm:
out["segments"] = norm
# A join always chooses a codec path: accurate=filter-concat re-encode,
# fast=demuxer-concat stream-copy (keyframe-snapped).
out["accurate"] = bool(spec.get("accurate", True))
return out
# Single TRIM (one output file; the frontend fans a "separate" split out into N of these).
trim = spec.get("trim") or {}
if trim:
start = max(0.0, float(trim.get("start_s") or 0.0))
end_raw = trim.get("end_s")
t: dict = {"start_s": round(start, 3)}
if end_raw is not None:
end = float(end_raw)
if end > start:
t["end_s"] = round(end, 3)
# A trim with only a start (open-ended) is valid (cut to the end).
if t.get("start_s") or "end_s" in t:
out["trim"] = t
# `accurate` only changes behaviour for a trim-only cut (a crop always re-encodes). Default to
# frame-accurate — an editor should cut where you asked; the user opts into fast/keyframe.
if out.get("trim") and "crop" not in out:
out["accurate"] = bool(spec.get("accurate", True))
return out
def edit_sig(spec: dict) -> str:
"""Stable 24-char signature of a (normalized) edit spec — the per-user cache identity."""
payload = json.dumps(normalize_edit_spec(spec), sort_keys=True, separators=(",", ":"))
return hashlib.sha256(payload.encode("utf-8")).hexdigest()[:24]
def has_crop(spec: dict) -> bool:
return bool(spec.get("crop"))
def needs_reencode(spec: dict) -> bool:
"""A crop always re-encodes; a trim re-encodes only when the user asked for an accurate cut."""
return bool(spec.get("crop")) or bool(spec.get("accurate"))
def clip_duration(spec: dict, source_duration: int | None) -> int | None:
"""Duration of the derived clip (seconds), for display + progress totals."""
segs = spec.get("segments")
if segs:
return max(0, round(sum(s["end_s"] - s["start_s"] for s in segs)))
trim = spec.get("trim")
if not trim:
return source_duration
start = trim.get("start_s") or 0.0
end = trim.get("end_s")
if end is None:
end = source_duration
if end is None:
return None
return max(0, round(end - start))
# --- ffmpeg: trim / crop --------------------------------------------------------------------
def build_edit_cmd(src: Path, dest: Path, spec: dict, out_ext: str) -> list[str]:
"""ffmpeg command for a trim/crop edit. `-progress pipe:1` streams machine-readable progress.
Trim uses fast input seek (`-ss` before `-i`) + `-t duration`, which is unambiguous across
ffmpeg versions. Trim-only stream-copies; a crop forces a re-encode (a filter can't be
stream-copied)."""
trim = spec.get("trim") or {}
start = trim.get("start_s") or 0.0
end = trim.get("end_s")
crop = spec.get("crop")
reencode = needs_reencode(spec)
cmd = [
"ffmpeg", "-y", "-hide_banner", "-loglevel", "error", "-nostdin",
"-progress", "pipe:1", "-nostats",
]
if start:
cmd += ["-ss", f"{start:.3f}"]
cmd += ["-i", str(src)]
if end is not None:
dur = end - start
if dur > 0:
cmd += ["-t", f"{dur:.3f}"]
if reencode:
# Input -ss + re-encode is frame-accurate (decodes from the prior keyframe, discards up to
# the exact cut). A crop adds the filter; an accurate trim re-encodes with no filter.
if crop:
cmd += ["-vf", f"crop={crop['w']}:{crop['h']}:{crop['x']}:{crop['y']}"]
cmd += [
"-c:v", "libx264", "-preset", "veryfast", "-crf", "20",
"-c:a", "aac", "-b:a", "192k",
]
else:
cmd += ["-c", "copy", "-avoid_negative_ts", "make_zero"]
if out_ext in ("mp4", "m4a", "mov"):
cmd += ["-movflags", "+faststart"]
cmd += [str(dest)]
return cmd
def build_concat_plan(src: Path, dest: Path, spec: dict, out_ext: str, staging: Path):
"""Plan a multi-segment JOIN (cut-list → one file). Returns (cmd, prep_files) where prep_files
maps a path → text content the worker must write before running (a concat list, if any).
* accurate/crop → filter_complex trim+concat, frame-accurate re-encode
* fast → concat demuxer with per-segment inpoint/outpoint, stream-copy
(keyframe-snapped, like the fast single trim)"""
segs: list[dict] = spec["segments"]
crop = spec.get("crop")
prep: dict[Path, str] = {}
head = [
"ffmpeg", "-y", "-hide_banner", "-loglevel", "error", "-nostdin",
"-progress", "pipe:1", "-nostats",
]
if needs_reencode(spec):
cropf = f",crop={crop['w']}:{crop['h']}:{crop['x']}:{crop['y']}" if crop else ""
parts, labels = [], []
for i, s in enumerate(segs):
st, en = s["start_s"], s["end_s"]
parts.append(f"[0:v]trim=start={st}:end={en},setpts=PTS-STARTPTS{cropf}[v{i}]")
parts.append(f"[0:a]atrim=start={st}:end={en},asetpts=PTS-STARTPTS[a{i}]")
labels.append(f"[v{i}][a{i}]")
parts.append(f"{''.join(labels)}concat=n={len(segs)}:v=1:a=1[v][a]")
cmd = head + [
"-i", str(src), "-filter_complex", ";".join(parts),
"-map", "[v]", "-map", "[a]",
"-c:v", "libx264", "-preset", "veryfast", "-crf", "20", "-c:a", "aac", "-b:a", "192k",
]
else:
listp = staging / "concat.txt"
lines = []
for s in segs:
lines.append(f"file '{src.as_posix()}'")
lines.append(f"inpoint {s['start_s']}")
lines.append(f"outpoint {s['end_s']}")
prep[listp] = "\n".join(lines) + "\n"
cmd = head + ["-f", "concat", "-safe", "0", "-i", str(listp), "-c", "copy"]
if out_ext in ("mp4", "m4a", "mov"):
cmd += ["-movflags", "+faststart"]
cmd += [str(dest)]
return cmd, prep
def _parse_out_time(line: str) -> float | None:
"""Parse a `-progress` line into elapsed output seconds."""
if line.startswith("out_time_us="):
try:
return int(line.split("=", 1)[1]) / 1_000_000
except ValueError:
return None
if line.startswith("out_time_ms="): # (some builds mislabel this as microseconds)
try:
return int(line.split("=", 1)[1]) / 1_000_000
except ValueError:
return None
return None
def run_ffmpeg(cmd, total_s, on_progress, should_cancel) -> None:
"""Run an ffmpeg edit, reporting 0100 progress and honouring cooperative cancel.
Raises EditAborted if should_cancel() turns True mid-run, RuntimeError on a nonzero exit."""
proc = subprocess.Popen(
cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True, bufsize=1
)
try:
assert proc.stdout is not None
for line in proc.stdout:
line = line.strip()
if should_cancel():
proc.terminate()
try:
proc.wait(timeout=5)
except subprocess.TimeoutExpired:
proc.kill()
raise EditAborted
secs = _parse_out_time(line)
if secs is not None and total_s:
on_progress(max(0.0, min(99.0, secs * 100.0 / total_s)))
finally:
if proc.stdout:
proc.stdout.close()
ret = proc.wait()
if ret != 0:
err = (proc.stderr.read() if proc.stderr else "") or ""
raise RuntimeError(f"ffmpeg failed ({ret}): {err[:300]}")
# --- filmstrip (editor scrub track) ---------------------------------------------------------
_SB_COLS = 12
_SB_TILE_W = 160
def storyboard_geometry(duration_s: int | None) -> dict:
"""Deterministic sprite geometry for a source duration (so meta is recomputable, unstored).
~1 frame / 5 s, clamped to fill a 12-wide grid of 24120 tiles."""
dur = max(1, int(duration_s or 1))
count = max(24, min(120, round(dur / 5)))
rows = math.ceil(count / _SB_COLS)
count = _SB_COLS * rows # fill the grid exactly
return {
"cols": _SB_COLS,
"rows": rows,
"count": count,
"interval_s": dur / count,
"tile_w": _SB_TILE_W,
}
def build_storyboard_cmd(src: Path, dest: Path, duration_s: int | None, geom: dict) -> list[str]:
"""One-pass tiled sprite. fps picks `count` frames evenly across the whole clip."""
dur = max(1, int(duration_s or 1))
fps = geom["count"] / dur
vf = f"fps={fps:.6f},scale={_SB_TILE_W}:-2,tile={geom['cols']}x{geom['rows']}"
return [
"ffmpeg", "-y", "-hide_banner", "-loglevel", "error", "-nostdin",
"-i", str(src), "-frames:v", "1", "-q:v", "5", "-vf", vf, str(dest),
]
def ensure_storyboard(asset, download_root: str, timeout_s: int = 90) -> dict | None:
"""Return the filmstrip meta for a ready source asset, generating the sprite on first use.
Best-effort + time-bounded: for a very long/high-res source the one-pass decode can be slow,
so it's capped by `timeout_s`; on timeout/failure we return None and the editor falls back to
a plain timeline (no filmstrip). Caches the sprite path on `asset.storyboard_path`.
Returns None (caller should NOT commit) if generation didn't happen; otherwise a meta dict and
sets `asset.storyboard_path` (caller commits)."""
if not asset.rel_path:
return None
geom = storyboard_geometry(asset.duration_s)
root = Path(download_root)
rel = f".storyboards/asset-{asset.id}.jpg"
dest = root / rel
if asset.storyboard_path and (root / asset.storyboard_path).exists():
return {**geom, "rel": asset.storyboard_path}
src = root / asset.rel_path
if not src.exists():
return None
dest.parent.mkdir(parents=True, exist_ok=True)
cmd = build_storyboard_cmd(src, dest, asset.duration_s, geom)
try:
subprocess.run(cmd, capture_output=True, timeout=timeout_s, check=True)
except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError) as exc:
log.info("storyboard gen skipped for asset %s: %s", asset.id, str(exc)[:120])
return None
if not dest.exists():
return None
asset.storyboard_path = rel # caller commits
return {**geom, "rel": rel}