Bendik Aagaard LynghaugandClaude Fable 5.1
9484d0d578
Records every source feeding the default sink into sample-aligned float WAV stems plus the sink mix, so sessions can be mixed and mastered later. Release flow mirrors galdr: tag -> build tarballs on both arches -> Gitea release -> publish to the uhhm Arch registry (no AUR package). Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
65 lines
2.8 KiB
Markdown
65 lines
2.8 KiB
Markdown
# stems
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Multitrack recorder for PipeWire. Run it, play your session, press Ctrl-C:
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every source that fed the default sink has its own WAV stem, plus the sink's
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mix as `00-master.wav`, all the same length and sample-aligned. Drop the
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folder into any DAW and mix or master later.
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```
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pw-play / galdr / browser / mic loopback ──▶ default sink ──▶ speakers
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│ │ │ │
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└── stems taps each source port ────────┴── 00-master (sink monitor)
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```
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## Usage
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```
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stems [--dir <path>] [--sink <node.name>] [--no-master] [--list]
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```
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- `--dir` session root, default `~/Recordings/stems`. Each run writes
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`<dir>/<YYYY-MM-DD_HH-MM-SS>/NN-<source>.wav`.
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- `--sink` record the sources of this sink instead of the default one.
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- `--no-master` skip `00-master.wav`.
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- `--list` print the sources that would be recorded right now and exit.
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Files are 32-bit float WAV at the graph rate, one per source node, with the
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source's channel count (mono sources stay mono). Sources that start mid-session
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get a track the moment they link to the sink; sources that stop keep their
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file. Ctrl-C (or SIGTERM) finalizes everything and prints a table:
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```
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# track ch length starts at dropped
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00 00-master.wav 2 42.67s 0.04s 0
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01 01-galdr.wav 2 42.67s 0.00s 0
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02 02-fc.zoom.playback.wav 2 42.67s 0.00s 0
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03 03-pw-play.wav 2 42.67s 12.30s 0
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```
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## How alignment works
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PipeWire stamps every graph cycle with one timestamp that all streams in that
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cycle see (`pw_time.now`). Each stem's first buffer is placed at that
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timestamp's distance from the session origin, cycles a stream missed are
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filled with silence, and at the end every file is padded to the common length.
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So frame N in one file is frame N in every other file; "starts at" in the
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table is just how much leading silence a late-joining track got.
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Each track is a capture stream linked by hand (`link-factory`) to the source's
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output ports, so the session manager never re-routes it, and the realtime
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callback only copies frames into a lock-free ring that a writer thread drains.
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## Limitations
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- A source that appears mid-session is tapped a few graph cycles after it
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starts (the link has to be created once the graph reports it), so roughly
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the first 30 to 50 ms of a new source are only in the master, not in its stem.
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- The default sink is read once at start; switching sinks during a session
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is not followed. Use `--sink` to pin one.
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- Stems capture what the source sends to the sink, pre-fader: the sink's
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per-stream volume is not applied (the master has it).
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## Build
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Rust, PipeWire 1.x. `cargo build --release`; the binary is `stems`.
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