Smaller videos. Same Mac. Nothing leaves it.

Why there is anything left to take

Already compressed doesn’t mean finished.

Video off an iPhone is H.265 already, the efficient format, so it looks like there is nothing left to squeeze. In practice there is a great deal, and the reason is the phone rather than the format.

• The waste is biggest in the easy footage: locked-off shots, plain backgrounds, anything slow. Those were given a budget sized for the hardest thing you might have filmed.

  HowCapture encoding runs single pass at a near constant rate from a fixed ladder chosen for the recording mode, with no lookahead and a hard latency and thermal budget, so bit allocation cannot follow scene complexity.

• Ounce re-spends that budget according to what each moment is actually worth.

  HowA constant quality target with full analysis re-allocates by real scene cost rather than holding a rate, so simple content collapses while difficult content keeps its bits.

A folder of fourteen iPhone clips, all of it H.265 to begin with, came back 211 MB lighter in under five minutes on an M1 Pro. The recording of that run is further down this page.

• Ounce checks your video before it starts. If compressing it would make the file bigger, it says so within a second or two and leaves your original alone.

  HowThree 2 second slices, sampled at 17%, 48% and 79% of the timeline, are encoded with the exact target settings before the real encode begins. If the predicted bitrate is 1.5 times the source or more, the job is declined.

• It errs towards trying. You will not be told no on a file that would have compressed perfectly well.

  HowThe 1.5 threshold is calibrated against eleven measured files across both encode paths rather than chosen by feel. Slice based probing over-estimates by 13% to 68%, so the threshold sits deliberately above 1.0.

• You can never end up with a file larger than the one you started with.

  HowPost-encode size gate: an output that is not strictly smaller than its input is deleted, never kept.

• Quality holds steady the whole way through. Fast, detailed scenes get the bits they need instead of falling apart exactly when it matters most.

  HowConstant quality rate control, not a fixed bitrate target. VideoToolbox AVVideoQualityKey at 0.65 / 0.52 / 0.40; libvpx and SVT-AV1 at CRF 32/40/47 and 30/40/48.

• Format
• Quality
• Size

• HEVC is the all-rounder, fastest and small. H.264 plays on absolutely anything, at the cost of a larger file.

  HowMP4 HEVC and MP4 H.264 encoded by VideoToolbox. Audio re-encoded to AAC.

• AV1 gives the smallest files of all and is the right choice for a website. VP9 plays in every modern browser, including older Safari.

  HowWebM AV1 via SVT-AV1 and WebM VP9 via libvpx. Audio re-encoded to Opus.

• Give it more or less any video file and it will read it.

  How19 input container types accepted: mp4, m4v, mov, avi, mpg, mpeg, mkv, m2ts, mts, ts, 3gp, wmv, flv, webm, ogv, mxf, asf, divx, vob.

• Colours come out the same as they went in, rather than shifting once the video is on the web.

  HowSource colour is read as CICP primaries, transfer and matrix, then written into the Matroska Colour element and the AV1 configuration record.

What protects your files

The part you only notice when it is missing.

Replacing originals is off until you turn it on, and when you do, the app explains itself first rather than just doing it.

• A half-written file is never mistaken for a finished one.

  HowEvery output is re-opened and its samples walked to the end before acceptance. Header checks alone are insufficient: MP4s are written moov-first, so a truncated file still reports full duration and track count.

• The safety check works on every format, not only the Apple ones.

  HowWebM outputs are verified with libwebm's own parser, because AVFoundation cannot read WebM at all and reports zero tracks.

• Originals go to the Trash, never straight to deletion, and only once there is a verified, smaller replacement. You can always get them back.

  HowReplace originals is off by default, calls trashItem and never removeItem, and runs only after the replacement is verified complete and confirmed smaller.

• A folder holding both clip.mov and clip.mp4 is completely normal, and nothing gets clobbered.

  HowOunce never writes over a file it did not create. A name collision produces a distinct filename instead.

• Stop means stop.

  HowStop halts the encode in progress, not merely the queue, in 0.3 to 0.5 seconds across all four codecs. Partial output is discarded.