CoreTrim

Formats CoreTrim trims

CoreTrim exports only the media your timeline actually uses — plus the handles you choose — and relinks your Final Cut Pro project to the new, smaller files. The formats below are trimmed without re-encoding (except where noted), so quality is identical to your originals.

Video — QuickTime & MP4

.mov · .mp4 · .m4v

Format	How it trims	Precision
Apple ProRes422 · 422 HQ · 422 LT · 4444 · 4444 XQ · RAW · RAW HQ	Lossless	Frame-exact
Avid DNxHD / DNxHR	Lossless	Frame-exact
H.264 / AVC	Lossless	Keyframe-aligned
HEVC / H.265	Lossless	Keyframe-aligned
MPEG-2 (Long-GOP)Sony XDCAM in QuickTime	Lossless	Keyframe-aligned

Other video that Final Cut Pro can read is also trimmable by re-encoding to ProRes — offered only with your approval, never automatically.

Video — Professional MXF

.mxf — broadcast & cinema cameras

Format	How it trims	Precision
Avid DNxHD / DNxHR	Lossless	Frame-exact
Apple ProRes (MXF-wrapped, e.g. ARRI)	Lossless	Frame-exact
MPEG-2 (Long-GOP)Sony XDCAM · Canon XF	Lossless	Keyframe-aligned
DV / DVCPRO (MXF-wrapped)	Lossless	Frame-exact
Uncompressed (MXF-wrapped)	Lossless	Frame-exact
PCM audio (MXF-wrapped)	Lossless	Sample-accurate

Video — AVCHD / camcorder

.mts · .m2ts

Format	How it trims	Precision
MPEG-2 (HDV-era .mts)	Lossless	Keyframe-aligned
H.264 (AVCHD)	Copied in full	Not trimmed

AVCHD camcorder footage is copied rather than trimmed, by design. Its recordings place true random-access frames roughly eight seconds apart, and trimming to anything less exact risks a clip that starts on the wrong frame — so CoreTrim copies these files intact instead. You lose the space saving on that footage, never the footage.

Audio

.wav · .aif · .aiff · .caf · .m4a · .mp3

Format	How it trims	Precision
PCMWAV · AIFF · CAF	Lossless	Sample-accurate
AAC (M4A) · MP3	Re-encoded to AAC	Sample-accurate

What the terms mean

Lossless: No re-encoding — the trimmed media is bit-for-bit the same quality as your original.
Frame-exact: Trimmed precisely to your edit points.
Keyframe-aligned: Long-GOP formats start at the nearest keyframe just before your edit (a fraction of a second). Still lossless, and your clip plays correctly from its exact in-point.
Sample-accurate: Audio is trimmed to the exact sample.
Re-encoded: Compressed audio is re-encoded to AAC (the only quality-affecting case above).

Cameras that trim

Common cameras & the formats CoreTrim trims from them

ARRI	ProRes (MXF & QuickTime)ARRIRAW is copied in full
Sony	XDCAM MPEG-2 (MXF & QuickTime) · α7 / FX mirrorless H.264 & HEVCX-OCN is copied in full
Canon	XF MPEG-2 (MXF) · EOS DSLR & mirrorless H.264 & HEVCCinema RAW Light is copied in full
Panasonic	Lumix H.264 & HEVCV-RAW and P2 are copied in full
Blackmagic · RED	ProRes (QuickTime)BRAW and REDCODE RAW are copied in full
GoPro · DJI · drones · iPhone	H.264 & HEVC

Timelines & multicam

CoreTrim trims your media however your timeline uses it

Multicam	By default only the angles your cut actually uses are trimmed — or keep every angle complete for future re-editing, or skip multicam entirely. Your choice, and the projected saving updates as you change it.
Compound & synchronized clips	Trimmed — CoreTrim looks inside them, at any nesting depth.
Auditions	Every take is trimmed — the one you picked and the alternatives you parked — so you can still switch takes after importing.
Connected clips, lanes & transitions	Kept in place — timing, keyframes, markers and split edits are preserved.

When a clip is copied instead of trimmed

All safe — the clip is copied in full, never altered

The clip is offline, or CoreTrim doesn't have permission to read it.
Your timeline already uses the whole clip — there's nothing to trim away.
It's a still image, or camera RAW from a manufacturer's own format — ARRIRAW, Canon Cinema RAW Light, Sony X-OCN, RED, Blackmagic BRAW, Panasonic V-RAW. These need the manufacturer's own software to open, so CoreTrim copies them untouched. (Apple ProRes RAW is the exception — it trims like any other ProRes.)
It's a specialized or unsupported source format, or AVCHD camcorder footage (see above).

And if a file can be neither trimmed nor copied — a damaged or unreadable source — CoreTrim leaves it out of the export and says so plainly in the report, rather than quietly linking your new project back to the original media.