Free online KUX to MTS converter

What the KUX format is

KUX is a proprietary video container associated with Youku downloads and offline playback. Youku software creates KUX files when saving streamed video for local use; the files commonly contain video and audio streams in a Youku-specific or modified streaming structure.

KUX is not a broadly supported interchange format. A file may play in the Youku client but fail in standard editors, television software, or hardware players. Some KUX downloads are encrypted or contain protection that prevents general-purpose converters from reading them.

What the MTS format is

MTS is an MPEG-2 transport stream, commonly used by AVCHD camcorders and Blu-ray-compatible workflows. It usually carries H.264/AVC video with AC-3 or LPCM audio, although generic MPEG-TS files can contain other codec combinations.

MTS supports high-definition video, multiple streams, time-based transport packets, and playback or editing in many video applications. It is suitable when a device or application specifically requests an AVCHD-style .mts file; it does not normally make a video smaller than the source.

How to actually convert KUX to MTS

Using the 101convert online converter

1. Open the KUX-to-MTS converter on 101convert.com.
2. Upload the .kux file and select MTS as the output format.
3. Start the conversion and download the resulting .mts file when processing finishes.

This method requires no installed software. It may fail when the KUX file is encrypted, damaged, or larger than the service accepts; use only files you are permitted to upload.

Using FFmpeg when the KUX stream is readable

Install a current FFmpeg build, open a terminal in the folder containing the source file, and inspect it first:

ffprobe input.kux

If FFmpeg identifies the streams, remux them without re-encoding:

ffmpeg -i input.kux -map 0 -c copy -f mpegts output.mts

Stream copying is faster and preserves the original encoded quality. If the source codecs are unsuitable for the target device, encode H.264 video and AC-3 audio instead:

ffmpeg -i input.kux -map 0:v:0 -map 0:a:0? -c:v libx264 -crf 18 -preset medium -c:a ac3 -b:a 192k -f mpegts output.mts

The optional audio mapping marker prevents failure when the KUX file has no audio stream. Replace input.kux and output.mts with the actual filenames.

Quality, compatibility, and limitations

Changing the container with -c copy does not improve quality and may retain codecs that an AVCHD device cannot decode. The re-encoding command produces a more broadly compatible H.264/AC-3 combination but introduces generation loss and takes substantially longer.

A KUX file that FFmpeg cannot probe is usually proprietary, encrypted, incomplete, or unsupported by that FFmpeg build. Renaming .kux to .mts does not convert the file. Obtain an unprotected source through the authorized Youku application or export a standard video file first, then convert that file to MTS.

After conversion, verify duration, audio synchronization, resolution, and playback on the intended device. Some AVCHD hardware accepts only specific frame rates, resolutions, bitrate limits, and directory structures; an isolated .mts file may play in software but still fail when copied directly to such hardware.