Free online KUX to AVI converter

Legacy video editors, hardware players, and archive workflows may require AVI instead of a downloaded Youku KUX file. Converting the file produces a standard container that those applications can inspect and play, provided the selected codecs are supported.

What the KUX format is

KUX is a proprietary video format associated with Youku downloads and the Youku desktop player. Youku users may receive it when saving videos for offline playback instead of downloading a standard MP4 or MKV file.

A KUX file can contain video and audio streams together with Youku-specific metadata or protection. The extension does not identify the internal codecs, and renaming .kux to .avi changes only the filename; it does not convert the media.

What the AVI format is

AVI, or Audio Video Interleave, is a Microsoft container supported by many older Windows applications, editing systems, media players, and hardware devices. It can contain codecs such as MPEG-4 Part 2, H.264, uncompressed video, PCM audio, and MP3 audio.

AVI is useful for legacy compatibility, but it generally produces larger files than modern MP4 encoding and does not define a single video or audio codec. A device that accepts AVI may still reject a file containing unsupported codecs. Subtitle tracks, metadata, and other KUX-specific features may also be lost during conversion.

How to convert the file

Using 101convert.com

1. Open the KUX-to-AVI converter on 101convert.com.
2. Upload the complete .kux file.
3. Choose AVI as the output format and start the conversion.
4. Download the resulting .avi file and test it in the application or device that requires AVI.

This method requires no installed software. Conversion can fail when the KUX file is incomplete, damaged, encrypted, or uses a variant the converter does not support. Uploading also requires transferring the source file to the service, so files containing sensitive material may be better handled locally.

Using FFmpeg

Some current FFmpeg builds can demux particular KUX variants. First test whether FFmpeg can read the source:

ffmpeg -i input.kux

If FFmpeg identifies the streams, create an AVI using codecs commonly accepted by older software:

ffmpeg -i input.kux -c:v mpeg4 -q:v 3 -c:a libmp3lame -q:a 3 output.avi

Replace input.kux with the actual filename. This command re-encodes the video as MPEG-4 Part 2 and the audio as MP3, rather than assuming that the original KUX codecs will be compatible with AVI playback. The libmp3lame encoder must be included in the installed FFmpeg build.

If FFmpeg reports Invalid data found when processing input, that build cannot parse the KUX variant or the file is protected or incomplete. A KUX-capable conversion program must first produce a standard video file; that file can then be converted to AVI with FFmpeg.

Quality and compatibility limits

Re-encoding cannot restore detail already lost in the source. In FFmpeg's MPEG-4 Part 2 encoder, a lower -q:v value generally gives higher quality and a larger file; test the result because acceptable values depend on the source and playback device. The audio -q:a 3 setting also uses variable bitrate MP3 encoding.

For older hardware, MPEG-4 Part 2 video with MP3 audio is often more compatible than H.264 with AAC inside AVI, but the device's specification takes priority. If the target application accepts MP4, it is usually a more space-efficient choice; use AVI when the receiving workflow specifically requires it.