video-compress-to-size · diff
git:20260812.225d65d to git:20260827.2ff136f
36 added, 8 removed. Audit A to A.
---
name: video-compress-to-size
- description: Compresses video files to stay under a user-specified max file size using FFmpeg. Prefers GPU encoders (NVENC / AMF / QSV) with VBR bitrate targeting; falls back to CPU two-pass H.264/HEVC. Use when the user wants to compress video, reduce video file size, shrink MP4/MKV/MOV under N MB, GPU encode, NVENC compress, 压缩视频, 缩小视频体积, or batch-compress clips to a size limit.
+ description: Compresses a single video file to stay under a user-specified max file size using FFmpeg. Prefers GPU encoders (NVENC / AMF / QSV) with VBR bitrate targeting; falls back to CPU two-pass H.264/HEVC. Use when the user wants to compress video, reduce video file size, shrink MP4/MKV/MOV under N MB, GPU encode, NVENC compress, 压缩视频, 缩小视频体积, or re-encode a clip to a size limit.
---
# Video Compress To Size
- Re-encode supported videos so each output is **at or under** a given max file size.
+ Re-encode a supported video so the output is **at or under** a given max file size.
**Default:** probe and use a GPU encoder when available (NVIDIA NVENC → AMD AMF → Intel QSV), single-pass VBR. If no GPU works, fall back to **CPU two-pass** (`libx264` / `libx265`).
## Rules
When this skill applies, read and follow [skill-dependency-manager](../skill-dependency-manager.md) — run scripts as documented, install missing tools into `.dependency/`.
+ - Run `compress.py` through **`.dependency/python/python.exe`**. Never use host `python` / `ffmpeg`.
+ - **Never overwrite sources.** Outputs go under `video-compress-to-size/`.
+ - Use the bundled script — do not hand-write equivalent FFmpeg commands.
+ - **One file per run** — pass `--video` with a single file; repeat for each clip in a batch.
+
## Quick Start
```bash
- .dependency/python/python .cursor/skills/video-compress-to-size/scripts/compress.py path/to/video_or_folder --max-size 50MB
+ .dependency/python/python .ai/video-compress-to-size/compress.py --video path/to/clip.mp4 --max-size 50MB
```
Bare numbers mean **MB** (`--max-size 50` ≡ `50MB`):
```bash
- .dependency/python/python .cursor/skills/video-compress-to-size/scripts/compress.py assets/intro.mp4 --max-size 50
+ .dependency/python/python .ai/video-compress-to-size/compress.py --video assets/intro.mp4 --max-size 50
```
+ Example:
+
+ ```
+ assets/video/intro.mp4
+ → assets/video/video-compress-to-size/intro.mp4
+ ```
+
Force CPU (slow, more precise two-pass):
```bash
- .dependency/python/python .cursor/skills/video-compress-to-size/scripts/compress.py clip.mp4 --max-size 50MB --cpu
+ .dependency/python/python .ai/video-compress-to-size/compress.py --video clip.mp4 --max-size 50MB --cpu
```
## Size Syntax
| Input | Meaning |
|-------|---------|
| `50` / `50MB` / `50M` | 50 mebibytes (1024² bytes) |
| `500KB` / `500K` | 500 kibibytes |
| `1GB` / `1G` | 1 gibibyte |
| `52428800B` | exact bytes |
`--max-size` is **required**.
## Format Defaults
| Setting | Default | Notes |
|---------|---------|-------|
| Encoder | GPU first | `h264_nvenc` → `h264_amf` → `h264_qsv` → `libx264` |
| HEVC | `--hevc` | Same order with `hevc_*` / `libx265` |
| Container | `.mp4` | Always MP4 |
| Audio | AAC 128k | Lowered automatically on tiny budgets |
| Preset | `medium` | Mapped (e.g. NVENC `p4`); override with `--preset` |
| Already under limit | Skipped | `[skip] … (already under limit)` |
| Safety margin | GPU ~90% / CPU ~92% | Headroom for mux / VBR overshoot |
## Common Flags
- `-r` · `-o` / `--output-dir` · `--max-size` · `--audio-bitrate` · `--preset` · `--hevc` · `--cpu` · `--overwrite` · `--dry-run`
+ `--video` · `--max-size` · `-o` / `--output` · `--audio-bitrate` · `--preset` · `--hevc` · `--cpu`
- **Never overwrite source files.** Writes only to `compressed/` (or `-o`). Supported inputs: `.mp4`, `.mkv`, `.mov`, `.avi`, `.webm`, `.wmv`, `.flv`, `.m4v`, `.mpeg`, `.mpg`, `.ts`, `.mts`, `.m2ts`, `.3gp`, `.ogv`, `.ogg`.
+ Custom output path:
+ ```bash
+ .dependency/python/python .ai/video-compress-to-size/compress.py --video clip.mp4 --max-size 50MB -o out/clip.mp4
+ ```
+
+ **Never overwrite source files.** Input must be a single video file (`--video`), not a directory. Supported inputs: `.mp4`, `.mkv`, `.mov`, `.avi`, `.webm`, `.wmv`, `.flv`, `.m4v`, `.mpeg`, `.mpg`, `.ts`, `.mts`, `.m2ts`, `.3gp`, `.ogv`.
+
## Agent Notes
1. Use the bundled script, not hand-written `ffmpeg` commands.
2. Always pass `--max-size` from the user (ask if missing). Prefer their unit wording; bare numbers are MB.
3. **Prefer GPU** — do not pass `--cpu` unless the user asks or GPU encode fails.
4. Do **not** downscale or change fps unless the user asks.
5. Sources already ≤ max size are skipped.
- 6. Tell the user where `compressed/` files are; they swap assets manually when ready.
+ 6. Tell the user where `video-compress-to-size/` files are; they swap assets manually when ready.
7. Missing Python/FFmpeg → populate `.dependency/` per skill-dependency-manager, retry same command.
8. Pipeline details: [reference.md](reference.md)
+
+ ## Tests
+
+ From repo root:
+
+ ```bash
+ .dependency/python/python .ai/video-compress-to-size/test_compress.py
+ ```
+
+ Manual CLI examples: [.ai/video-compress-to-size/test.md](../../../.ai/video-compress-to-size/test.md)