ergosteur
ac3bdbcfe9
Distinguishes a genuine audio mismatch at a clip boundary (evidence the inputs aren't really a continuous sequence) from a boundary that's simply too quiet to judge either way, using an RMS floor alongside the existing cross-correlation confidence score. A confident mismatch now aborts before encoding instead of silently splicing unrelated clips together; --allow-discontinuous opts back into the old behavior.
101 lines
4.5 KiB
Markdown
101 lines
4.5 KiB
Markdown
# live-photo-concat
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Concatenate sequential iPhone Live Photo `.MOV` clips into a single seamless,
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metadata-preserving video — with the real duplicate footage between clips
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removed.
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## Why
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Each iPhone Live Photo `.MOV` captures roughly 1.5 seconds before and after
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its key moment. When several Live Photos are taken in quick succession (e.g.
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rapid-fire shutter presses), consecutive clips genuinely overlap: the same
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seconds of real-world video and audio get captured twice, once at the end of
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clip *N* and again at the start of clip *N+1*. Naively concatenating the
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clips repeats that footage, which shows up as an odd "loop" at each clip
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boundary.
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This script:
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1. Extracts the real video+audio streams from each clip (iPhone Live Photo
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files bundle a handful of extra HDR/depth/metadata tracks that aren't
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needed here).
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2. Cross-correlates the audio at each clip boundary to measure the *actual*
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overlap duration from the content itself (not just filename order or
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whole-second creation timestamps, which aren't precise enough). If a
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boundary's audio simply doesn't match — a sign the inputs aren't actually
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a continuous sequence (wrong order, a missing clip, unrelated files) — the
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run aborts before encoding anything, rather than silently splicing
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together clips that don't belong together.
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3. Trims the duplicated span off the start of each subsequent clip.
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4. Re-encodes the video across the joins (trimming mid-GOP HEVC can't be done
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with a plain stream copy) and concatenates everything into one file.
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5. Carries over the original container metadata (GPS, device info, creation
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time, Live Photo identifiers) from one of the source clips.
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Audio stays uncompressed PCM throughout, so it never loses quality. Video
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quality defaults to a bitrate slightly above the source clips' own bitrate
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(configurable — see below).
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## Requirements
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- `ffmpeg` / `ffprobe` on `PATH`
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- Python 3 with the packages in `requirements.txt`:
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```bash
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pip install --user -r requirements.txt
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```
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## Usage
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```bash
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./concat_live_clips.py IMG_2441.MOV IMG_2442.MOV IMG_2443.MOV ...
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./concat_live_clips.py -o myvideo.mov clip1.MOV clip2.MOV ...
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```
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If `-o/--output` is omitted, the output filename is derived from the source
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filenames' numbering, e.g. `IMG_2441.MOV .. IMG_2445.MOV` produces
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`IMG_2441-2445.mov`.
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### Numbered sequence shortcuts
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```bash
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# bash / zsh
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./concat_live_clips.py IMG_{2441..2445}.MOV
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# PowerShell
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python .\concat_live_clips.py (2441..2445 | ForEach-Object { "IMG_$_.MOV" })
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```
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### Options
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| Flag | Description |
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|---|---|
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| `-o, --output` | Output file path (default: derived from source filenames) |
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| `--crf N` | Use CRF (quality-based) encoding instead of the default bitrate target. Lower = higher quality; ~14-18 is near-transparent |
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| `--bitrate RATE` | Explicit target video bitrate, e.g. `12M` or `12000k` |
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| `--lossless` | Mathematically lossless video encoding (much larger output) |
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| `--bitrate-multiplier N` | When auto-selecting a bitrate, multiply the source clips' peak bitrate by this (default: `1.2`) |
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| `--bitrate-floor RATE` | When auto-selecting a bitrate, never go below this (default: `10M`) |
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| `--preset` | x265 preset (default: `medium`) |
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| `--metadata-from N` | Take container metadata from the Nth input clip, 0-indexed (default: `0`, the first clip) |
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| `--confidence-threshold N` | Minimum audio cross-correlation confidence required to trust an overlap detection before falling back to 0 (default: `0.9`) |
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| `--min-signal-rms N` | Below this audio RMS level (int16 scale), a boundary is considered too quiet to judge continuity, so a low-confidence match there won't trigger an abort (default: `25`) |
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| `--allow-discontinuous` | Proceed even if audio at a clip boundary doesn't match, instead of aborting |
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`--crf`, `--bitrate`, and `--lossless` are mutually exclusive; the default
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(no flag) auto-computes a bitrate target from the source clips.
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### Continuity check
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Before encoding, each clip boundary's audio is checked for a real match.
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Three outcomes:
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- **Confident match** (confidence ≥ `--confidence-threshold`) — the overlap
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is measured and trimmed as normal.
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- **Too quiet to tell** (signal below `--min-signal-rms`) — treated as 0
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overlap and the run proceeds, since there's no reliable signal either way.
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- **Confident mismatch** (enough signal, but it doesn't correlate) — treated
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as evidence the clips aren't actually a continuous sequence, and the run
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aborts with an error before any encoding happens. Pass
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`--allow-discontinuous` to concatenate them anyway.
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