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Muxsmith for macOS

Your video library toolkit for Mac.

Remux, split, join, rename, and transcribe videos in one Mac app. Choose the tracks you want, batch repetitive work, and generate subtitles locally on Apple silicon Macs running macOS 26 or later. Source files are never overwritten.

Download Muxsmith 1.2.0 See what it does

Version 1.2.0 · macOS 14+ · Apple silicon and Intel

Muxsmith app icon concept

No video re-encodeCompatible video and audio are copied unchanged

Track-by-track controlChoose languages, commentary and subtitles

Best-effort batch matchingRepeat confident choices and review the rest

Processing stays localYour media is not uploaded

MKV to MP4 without re-encoding

Change the container. Keep the video quality.

Convert compatible MKV files to MP4 without re-encoding video or audio. Keep the tracks you want, remove the ones you don’t, and review every change before it runs. This container-only conversion is called remuxing, and it is generally much faster than transcoding because the existing video and audio are copied into a new file.

Use Muxsmith

The picture and sound are already encoded the way you want.

Convert a compatible MKV to MP4, remove extra tracks, or split and join files with stream copy. Muxsmith does not re-encode or compress the remaining video and audio.

Use HandBrake

You need to change the video or audio itself.

HandBrake is suited to a different codec, lower resolution or bitrate, device-targeted transcoding, or video compression.

What you can change

Choose the container and every track in the output.

Muxsmith shows the codec, language, title, dimensions, channels and flags before you run a job. Every media operation writes a new output file.

01 · MKV to MP4

Convert a compatible MKV to MP4 without re-encoding.

Muxsmith remuxes selected video and audio into MP4, MOV, MKV, M4V or WebM. Compatible streams are copied unchanged. Selected text subtitles are converted only when the destination container requires another text format.

02 · Smaller output

Remove tracks you do not need.

Dropping an extra audio language, commentary track or subtitle can make the output smaller by the size of those tracks. Muxsmith does not compress or re-encode the remaining video.

03 · Track selection

Keep the main audio. Remove the commentary.

Choose video, audio and subtitle tracks independently for every file. Keep English 5.1 and English SDH, for example, while leaving out a commentary mix.

VideoHEVC · 3840 × 2160Keep
AudioEnglish · 5.1Keep
AudioCommentary · StereoRemove
SubtitleEnglish · SDHKeep

04 · Batch matching

Repeat one track choice across confident matches.

Muxsmith matches stream type and language, then considers roles such as commentary, forced, SDH and descriptive audio. A confident match can receive the same keep or remove choice. Ambiguous or missing matches stay unchanged for review, and Muxsmith reports how many files it updated.

05 · Split

Choose a range or split point with a visual preview.

Scrub, step backward or forward one frame, and use the playhead for a clip range or two-part split. Outputs use stream copy, so a cut may align to a nearby keyframe.

06 · Join

Join compatible files in the order you choose.

Combine two or more files without re-encoding. A join with stream copy requires matching codecs and stream layouts.

07 · Sequence rename

Turn a folder of episodes into a clean sequence.

Preview show, season and episode names across a batch. Natural filename ordering, collision checks and a two-phase rename protect swaps and existing files.

08 · Queue and progress

Prepare several jobs, then run them in order.

Add work to a deferred queue or put a remux ahead of waiting jobs. Muxsmith processes one job at a time, shows progress when duration is available, and lets you cancel the current job.

  1. Episode 01.mkvRunning · 68%
  2. Episode 02.mkvWaiting
  3. Episode 03.mkvWaiting

New in Muxsmith 1.2

Transcribe your videos and generate subtitles, all locally on your Mac.

Select an audio track and spoken language. On an Apple silicon Mac running macOS 26 or later, Muxsmith uses Apple’s Speech framework to generate the transcript locally. Review and edit it before you export.

  1. 01

    Choose an audio track.

    Pick the audio track and spoken language you want to transcribe. This can be the main mix, commentary, or another language.

  2. 02

    Review and edit the transcript.

    Edit the generated text, search one transcript or several files, and adjust timing while you watch the video in a vertical conversation timeline. Add chapter markers where you need them.

  3. 03

    Export subtitles or a new video file.

    Save an SRT, or write a new MP4, M4V, MOV, MKV, or WebM. Compatible video and audio are stream-copied rather than re-encoded.

English · Main audio Review

We should take the coast road in the morning.

It will be quieter before the ferries arrive.

I’ll mark the turn after the old bridge.

Chapter · The coast road

Batch work

Follow the progress of each file.

Muxsmith shows progress for each file as it inspects the source, extracts the chosen audio, and creates the transcript. Cancel processing when needed, then batch-export the selected files.

Local review

Check timing against a local video preview.

When you review subtitle timing from an MKV, Muxsmith may create a temporary preview on your Mac. The source media, extracted audio, preview, and transcript stay on the Mac.

Files stay on your Mac

Your original files are never overwritten.

Muxsmith reads the files you choose and writes each result as a new output.

No uploadsMedia processing runs locally.
No accountThere is no Muxsmith sign-up.
No usage trackingMuxsmith does not record what you do. Weekly update checks can send five system fields described in Privacy.
Bundled toolsFFmpeg and ffprobe ship with the app, with their required notices and source.

Questions before you start

Files, tracks, and transcription.

Changing a container preserves compatible streams. Local transcription requires Apple silicon and macOS 26 or later.

Does converting MKV to MP4 reduce quality?

Compatible video and audio streams are copied unchanged, so they are not re-encoded. If a selected text subtitle must be converted for MP4, some subtitle styling can be simplified.

Will changing MKV to MP4 make it play on an iPhone?

There is no universal guarantee. Playback depends on the container, video codec and profile, audio, subtitles and the device’s support. Muxsmith 1.0 does not transcode incompatible video or audio.

How is Muxsmith different from HandBrake?

Muxsmith preserves compatible video and audio when you change a container, remove tracks, split or join. HandBrake is appropriate when you need re-encoding, compression, a different codec, or output tailored to a device.

Can removing audio tracks reduce file size?

Yes. The output is smaller by the size of the tracks you remove, so savings vary. Muxsmith does not recompress the remaining video.

Why are some subtitles converted or omitted?

Muxsmith copies compatible subtitles. It converts selected text subtitles when the destination container requires another text format, which can simplify styling. If a bitmap subtitle is not supported by the chosen container, Muxsmith marks it and asks for confirmation before leaving it out.

Does Muxsmith upload my audio or transcript?

No. Muxsmith uses Apple’s Speech framework to create transcripts locally on your Mac. macOS may download the selected language’s speech model from Apple, but Muxsmith does not upload media audio or transcript text. Transcription in Muxsmith 1.2 requires Apple silicon and macOS 26 or later.

Version 1.2.0 · Direct download

Download Muxsmith for Mac.

A signed and notarized DMG for macOS 14 or later, compatible with Apple silicon and Intel Macs. Approximately 64 MB.

Download Muxsmith 1.2.0 Download details

SHA-256ee650e2a12da5af699ca302b5f13c81ad8eb2d49374ad4df9edf5285c664eda6

From Nanda Kusumadi

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