Free online KUX to MPG converter

What the KUX format is

KUX is a proprietary video container associated with Youku downloads and the Youku desktop client. You encounter it when saving offline video from Youku rather than when recording or exporting from mainstream editing software.

A KUX file may contain video and audio in codecs such as H.264 and AAC, but its wrapper can include Youku-specific headers, segmentation, or encryption. Because of that, support varies between media applications: some FFmpeg builds can read particular KUX files, while others report an invalid or unsupported format.

What the MPG format is

MPG usually refers to an MPEG program stream containing MPEG-1 or MPEG-2 video and commonly MP2 or MPEG-1 Layer II audio. It is accepted by many older televisions, DVD-authoring applications, broadcast utilities, and legacy video editors.

MPG favors compatibility over compression efficiency. An MPEG-2 MPG file is generally larger than an equivalent H.264 or H.265 file, but it is easier for older hardware and software to decode without additional codecs.

How to actually convert KUX to MPG

Using the built-in online converter

1. Open the KUX-to-MPG converter on 101convert.com; the service can be used for free without installing software.
2. Select input.kux as the source file and choose MPG as the output format.
3. Start the conversion and download the resulting output.mpg when processing finishes.
4. Test the output from beginning to end, especially if the source was an offline or segmented Youku download.

Using FFmpeg on a desktop

First test whether the installed FFmpeg build can decode the KUX container directly:

ffmpeg -i input.kux -c copy test.mpg

This command only attempts stream copying and may fail because MPG requires compatible MPEG video and audio streams. For a normal MPEG-2 program stream, re-encode the source instead:

ffmpeg -i input.kux -c:v mpeg2video -pix_fmt yuv420p -q:v 3 -c:a mp2 -b:a 192k -ar 48000 -f mpeg output.mpg

-q:v 3 gives relatively high MPEG-2 quality; use a larger value for a smaller file and lower quality. If the source has no audio stream, add -an. If FFmpeg cannot identify input.kux, the file may use a Youku-specific encoding or protection method that the installed build cannot decode.

Quality, compatibility, and limitations

Conversion cannot restore detail already lost in the KUX source. Re-encoding to MPEG-2 normally increases file size and introduces another generation of compression, so retain the original KUX when it is still playable.

Choose MPEG-2 MPG when the destination specifically requires an MPEG program stream. If the receiving application accepts modern formats, MP4 with H.264 video is usually smaller and more suitable for general playback.

Some Youku downloads are protected, account-dependent, incomplete, or split into multiple files. A converter cannot reliably process a partial download or bypass access restrictions; obtain a complete, legitimately playable source first. Check the converted file's resolution, frame rate, audio synchronization, and duration before deleting the original.