Initial CutScript release - Open-source AI-powered text-based video editor
CutScript is a local-first, Descript-like video editor where you edit video by editing text. Delete a word from the transcript and it's cut from the video. Features: - Word-level transcription with WhisperX - Text-based video editing with undo/redo - AI filler word removal (Ollama/OpenAI/Claude) - AI clip creation for shorts - Waveform timeline with virtualized transcript - FFmpeg stream-copy (fast) and re-encode (4K) export - Caption burn-in and sidecar SRT generation - Studio Sound audio enhancement (DeepFilterNet) - Keyboard shortcuts (J/K/L, Space, Delete, Ctrl+Z/S/E) - Encrypted API key storage - Project save/load (.aive files) Architecture: - Electron + React + Tailwind (frontend) - FastAPI + Python (backend) - WhisperX for transcription - FFmpeg for video processing - Multi-provider AI support Performance optimizations: - RAF-throttled time updates - Zustand selectors for granular subscriptions - Dual-canvas waveform rendering - Virtualized transcript with react-virtuoso Built on top of DataAnts-AI/VideoTranscriber, completely rewritten as a desktop application. License: MIT
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backend/services/video_editor.py
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271
backend/services/video_editor.py
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"""
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FFmpeg-based video cutting engine.
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Uses stream copy for fast, lossless cuts and falls back to re-encode when needed.
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"""
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import logging
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import subprocess
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import tempfile
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import os
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from pathlib import Path
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from typing import List
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logger = logging.getLogger(__name__)
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def _find_ffmpeg() -> str:
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"""Locate ffmpeg binary."""
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for cmd in ["ffmpeg", "ffmpeg.exe"]:
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try:
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subprocess.run([cmd, "-version"], capture_output=True, check=True)
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return cmd
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except (FileNotFoundError, subprocess.CalledProcessError):
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continue
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raise RuntimeError("FFmpeg not found. Install it or add it to PATH.")
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def export_stream_copy(
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input_path: str,
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output_path: str,
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keep_segments: List[dict],
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) -> str:
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"""
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Export video using FFmpeg concat demuxer with stream copy.
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~100x faster than re-encoding. No quality loss.
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Args:
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input_path: source video file
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output_path: destination file
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keep_segments: list of {"start": float, "end": float} to keep
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Returns:
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output_path on success
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"""
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ffmpeg = _find_ffmpeg()
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input_path = str(Path(input_path).resolve())
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output_path = str(Path(output_path).resolve())
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if not keep_segments:
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raise ValueError("No segments to export")
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temp_dir = tempfile.mkdtemp(prefix="aive_export_")
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try:
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segment_files = []
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for i, seg in enumerate(keep_segments):
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seg_file = os.path.join(temp_dir, f"seg_{i:04d}.ts")
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cmd = [
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ffmpeg, "-y",
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"-ss", str(seg["start"]),
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"-to", str(seg["end"]),
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"-i", input_path,
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"-c", "copy",
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"-avoid_negative_ts", "make_zero",
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"-f", "mpegts",
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seg_file,
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]
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logger.info(f"Extracting segment {i}: {seg['start']:.2f}s - {seg['end']:.2f}s")
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result = subprocess.run(cmd, capture_output=True, text=True)
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if result.returncode != 0:
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logger.warning(f"Stream copy segment {i} failed, will try re-encode: {result.stderr[-200:]}")
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return export_reencode(input_path, output_path, keep_segments)
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segment_files.append(seg_file)
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concat_str = "|".join(segment_files)
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cmd = [
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ffmpeg, "-y",
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"-i", f"concat:{concat_str}",
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"-c", "copy",
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"-movflags", "+faststart",
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output_path,
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]
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logger.info(f"Concatenating {len(segment_files)} segments -> {output_path}")
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result = subprocess.run(cmd, capture_output=True, text=True)
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if result.returncode != 0:
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logger.warning(f"Concat failed, falling back to re-encode: {result.stderr[-200:]}")
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return export_reencode(input_path, output_path, keep_segments)
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return output_path
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finally:
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for f in os.listdir(temp_dir):
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try:
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os.remove(os.path.join(temp_dir, f))
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except OSError:
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pass
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try:
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os.rmdir(temp_dir)
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except OSError:
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pass
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def export_reencode(
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input_path: str,
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output_path: str,
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keep_segments: List[dict],
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resolution: str = "1080p",
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format_hint: str = "mp4",
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) -> str:
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"""
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Export video with full re-encode. Slower but supports resolution changes,
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format conversion, and avoids stream-copy edge cases.
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"""
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ffmpeg = _find_ffmpeg()
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input_path = str(Path(input_path).resolve())
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output_path = str(Path(output_path).resolve())
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if not keep_segments:
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raise ValueError("No segments to export")
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scale_map = {
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"720p": "scale=-2:720",
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"1080p": "scale=-2:1080",
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"4k": "scale=-2:2160",
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}
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filter_parts = []
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for i, seg in enumerate(keep_segments):
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filter_parts.append(
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f"[0:v]trim=start={seg['start']}:end={seg['end']},setpts=PTS-STARTPTS[v{i}];"
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f"[0:a]atrim=start={seg['start']}:end={seg['end']},asetpts=PTS-STARTPTS[a{i}];"
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)
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n = len(keep_segments)
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concat_inputs = "".join(f"[v{i}][a{i}]" for i in range(n))
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filter_parts.append(f"{concat_inputs}concat=n={n}:v=1:a=1[outv][outa]")
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filter_complex = "".join(filter_parts)
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scale = scale_map.get(resolution, "")
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if scale:
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filter_complex += f";[outv]{scale}[outv_scaled]"
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video_map = "[outv_scaled]"
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else:
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video_map = "[outv]"
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codec_args = ["-c:v", "libx264", "-preset", "medium", "-crf", "18", "-c:a", "aac", "-b:a", "192k"]
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if format_hint == "webm":
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codec_args = ["-c:v", "libvpx-vp9", "-crf", "30", "-b:v", "0", "-c:a", "libopus"]
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cmd = [
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ffmpeg, "-y",
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"-i", input_path,
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"-filter_complex", filter_complex,
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"-map", video_map,
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"-map", "[outa]",
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*codec_args,
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"-movflags", "+faststart",
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output_path,
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]
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logger.info(f"Re-encoding {n} segments -> {output_path} ({resolution})")
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result = subprocess.run(cmd, capture_output=True, text=True)
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if result.returncode != 0:
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raise RuntimeError(f"FFmpeg re-encode failed: {result.stderr[-500:]}")
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return output_path
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def export_reencode_with_subs(
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input_path: str,
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output_path: str,
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keep_segments: List[dict],
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subtitle_path: str,
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resolution: str = "1080p",
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format_hint: str = "mp4",
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) -> str:
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"""
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Export video with re-encode and burn-in subtitles (ASS format).
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Applies trim+concat first, then overlays the subtitle file.
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"""
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ffmpeg = _find_ffmpeg()
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input_path = str(Path(input_path).resolve())
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output_path = str(Path(output_path).resolve())
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subtitle_path = str(Path(subtitle_path).resolve())
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if not keep_segments:
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raise ValueError("No segments to export")
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scale_map = {
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"720p": "scale=-2:720",
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"1080p": "scale=-2:1080",
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"4k": "scale=-2:2160",
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}
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filter_parts = []
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for i, seg in enumerate(keep_segments):
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filter_parts.append(
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f"[0:v]trim=start={seg['start']}:end={seg['end']},setpts=PTS-STARTPTS[v{i}];"
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f"[0:a]atrim=start={seg['start']}:end={seg['end']},asetpts=PTS-STARTPTS[a{i}];"
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)
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n = len(keep_segments)
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concat_inputs = "".join(f"[v{i}][a{i}]" for i in range(n))
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filter_parts.append(f"{concat_inputs}concat=n={n}:v=1:a=1[outv][outa]")
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filter_complex = "".join(filter_parts)
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# Escape path for FFmpeg subtitle filter (Windows backslashes need escaping)
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escaped_sub = subtitle_path.replace("\\", "/").replace(":", "\\:")
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scale = scale_map.get(resolution, "")
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if scale:
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filter_complex += f";[outv]{scale},ass='{escaped_sub}'[outv_final]"
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else:
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filter_complex += f";[outv]ass='{escaped_sub}'[outv_final]"
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video_map = "[outv_final]"
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codec_args = ["-c:v", "libx264", "-preset", "medium", "-crf", "18", "-c:a", "aac", "-b:a", "192k"]
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if format_hint == "webm":
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codec_args = ["-c:v", "libvpx-vp9", "-crf", "30", "-b:v", "0", "-c:a", "libopus"]
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cmd = [
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ffmpeg, "-y",
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"-i", input_path,
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"-filter_complex", filter_complex,
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"-map", video_map,
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"-map", "[outa]",
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*codec_args,
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"-movflags", "+faststart",
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output_path,
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]
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logger.info(f"Re-encoding {n} segments with subtitles -> {output_path} ({resolution})")
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result = subprocess.run(cmd, capture_output=True, text=True)
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if result.returncode != 0:
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raise RuntimeError(f"FFmpeg re-encode with subs failed: {result.stderr[-500:]}")
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return output_path
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def get_video_info(input_path: str) -> dict:
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"""Get basic video metadata using ffprobe."""
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ffmpeg = _find_ffmpeg()
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ffprobe = ffmpeg.replace("ffmpeg", "ffprobe")
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cmd = [
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ffprobe, "-v", "quiet",
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"-print_format", "json",
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"-show_format", "-show_streams",
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str(input_path),
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]
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try:
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result = subprocess.run(cmd, capture_output=True, text=True, check=True)
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import json
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data = json.loads(result.stdout)
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fmt = data.get("format", {})
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video_stream = next((s for s in data.get("streams", []) if s.get("codec_type") == "video"), {})
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return {
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"duration": float(fmt.get("duration", 0)),
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"size": int(fmt.get("size", 0)),
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"format": fmt.get("format_name", ""),
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"width": int(video_stream.get("width", 0)),
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"height": int(video_stream.get("height", 0)),
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"codec": video_stream.get("codec_name", ""),
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"fps": eval(video_stream.get("r_frame_rate", "0/1")) if "/" in video_stream.get("r_frame_rate", "") else 0,
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}
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except Exception as e:
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logger.error(f"Failed to get video info: {e}")
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return {}
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