Performance

Subforge is tuned for large subtitle sets and supports fast paths for common patterns.

Benchmarks

Run the full benchmark suite:

bun run bench

100k parse benchmark

These numbers are from isolated runs (each format executed in its own process) using bun tests/bench/quick-isolated.ts --sort.

Format	100k parse (ms)
VobSub none	4.59
DVB	5.03
VobSub idx	6.93
PAC	7.21
Teletext	8.74
SBV	11.61
SCC	11.74
DFXP	12.52
TTML	12.53
SMPTE-TT	12.88
LRC	13.02
RealText	14.31
QT	14.60
ASS	15.21
SSA	15.44
Spruce STL	15.75
SAMI	16.28
EBU-STL	16.28
PGS	17.48
CAP	17.70
VobSub	18.88
VobSub rle	19.09

Results vary by hardware and Bun version. Re-run the command to refresh numbers. VobSub numbers assume the .idx is parsed once (see VobSub idx row); the VobSub row measures .sub parsing + image decode.

Quick 100k parse matrix:

bun tests/bench/quick.ts

Isolated per-format matrix (avoids GC drift):

bun tests/bench/quick-isolated.ts --sort

Tips

• Prefer subpath entry points to reduce bundle size.
• Keep event.dirty false when you do not need to reserialize text.