Free online KUX to M2TS converter

KUX files are commonly downloaded from Youku and may not open in standard video editors or players. Converting them to M2TS can make compatible, non-DRM video streams usable with Blu-ray, AVCHD, and MPEG transport-stream workflows.

What the KUX format is

KUX is a proprietary video container associated primarily with Youku downloads and offline playback. The Youku desktop or mobile application can save downloaded programs with the .kux extension, sometimes alongside segmented or cached data.

A KUX file may contain H.264 or another video codec, AAC audio, subtitles, and Youku-specific metadata. Some downloads are encrypted or protected for playback inside Youku software. Because KUX is not a broadly standardized exchange format, ordinary media players and editors may reject it even when its underlying streams use common codecs.

What the M2TS format is

M2TS is a transport-stream container used by Blu-ray discs, AVCHD cameras, and some broadcast and authoring workflows. It stores packetized audio, video, subtitles, and program metadata in a form designed for streaming and recovery from transmission errors.

M2TS is suitable when a Blu-ray or AVCHD-compatible application expects a transport stream rather than a web-video container. It can carry H.264 video with AAC, AC-3, or other supported audio, but changing the container does not make an unsupported codec or protected source compatible.

How to convert KUX to M2TS

Using 101convert.com

You can convert the file on the 101convert.com website for free without installing software. Upload the KUX file, select M2TS as the output format, start the conversion, and save the resulting file. This method works only when the service can decode the particular KUX variant and the file is not protected by Youku DRM.

Using FFmpeg

FFmpeg is appropriate when it recognizes the KUX container and can read its streams.

1. Install a current FFmpeg build and place the input file in a working folder.
2. Inspect the source with ffprobe input.kux. Confirm that FFmpeg detects video and audio streams rather than reporting an invalid or encrypted file.
3. Try a lossless container conversion with ffmpeg -i input.kux -map 0 -c copy -mpegts_m2ts_mode 1 output.m2ts. The -c copy option copies the encoded streams without decoding or quality loss.
4. If the target application does not accept the copied streams, re-encode to broadly supported codecs with ffmpeg -i input.kux -map 0:v:0 -map 0:a:0? -c:v libx264 -preset medium -crf 18 -c:a ac3 -b:a 384k -mpegts_m2ts_mode 1 output.m2ts.
5. Test output.m2ts in the intended player, editor, or authoring program. Inspect synchronization, subtitles, and audio-channel mapping before deleting the source.

If FFmpeg reports that the KUX file is encrypted, malformed, or unsupported, changing the extension will not fix it. Use the official Youku application to obtain an authorized playable export, or use a converter that specifically supports that KUX variant; do not attempt to bypass DRM.

Quality, compatibility, and limitations

Stream copying preserves the original encoded quality, but the resulting M2TS remains limited by the source codecs and resolution. Re-encoding reduces quality and increases processing time, although H.264 video and AC-3 audio generally provide good compatibility with M2TS-oriented software.

M2TS is a container, not a guarantee of Blu-ray compliance. Disc authoring may require specific H.264 profiles, frame rates, bit rates, audio formats, and folder structures. Some converters omit KUX subtitles, chapter markers, thumbnails, or proprietary metadata. Check the output with ffprobe output.m2ts and verify each stream before authoring or archiving.