Free online ISMV to DIVX converter

What the ISMV format is

ISMV is the video fragment format used by Microsoft IIS Smooth Streaming. It is based on fragmented MPEG-4 and commonly contains H.264 video with AAC audio. Microsoft IIS Media Services, Microsoft Expression Encoder, and related Smooth Streaming workflows create ISMV fragments, usually alongside an .ism server manifest and separate audio fragments.

An ISMV file may not behave like an ordinary MP4 because it is designed for adaptive streaming rather than direct playback. Some files are also protected by DRM; encrypted content cannot be converted unless it is legally available in an unencrypted form.

What the DIVX format is

DivX usually refers to MPEG-4 Part 2 video encoded with the DivX codec, commonly stored in an AVI container and identified by the DX50 FourCC. DivX files are supported by many older standalone DVD players, televisions, car media systems, and software players.

DivX can provide smaller files than uncompressed or lightly compressed video, but it is an older format. H.264 MP4 generally gives better quality at the same bitrate, so DivX is mainly appropriate when a specific device or application requires it.

How to actually convert ISMV to DIVX

FFmpeg is the most reliable desktop option because it can demux fragmented MP4 input and encode MPEG-4 Part 2 output. Install a current FFmpeg build, place the ISMV file in an accessible folder, and run:

ffmpeg -i input.ismv -c:v mpeg4 -vtag DX50 -q:v 3 -c:a libmp3lame -b:a 128k -ar 48000 -f avi output.divx

This command reads input.ismv, encodes the video as MPEG-4 Part 2 with the DivX-compatible DX50 tag, converts audio to MP3, and writes an AVI-format file named output.divx. The extension is only a filename label; the AVI container and codec tags determine compatibility.

For a stricter older-player profile, use a smaller frame size and a fixed bitrate, for example:

ffmpeg -i input.ismv -vf scale=720:-2 -c:v mpeg4 -vtag DX50 -b:v 1500k -c:a libmp3lame -b:a 128k -ar 48000 -f avi output.divx

Check the source streams before converting with:

ffprobe input.ismv

If the ISMV is one fragment from a Smooth Streaming presentation, converting only that fragment produces only its available duration. When the complete presentation is available, use the original manifest or combine the required fragments first; a lone fragment cannot reconstruct missing video or audio.

For a no-installation option, upload the file to the built-in converter on 101convert.com, choose DIVX as the output format, start the conversion, and download the result. This option is unsuitable for confidential or DRM-protected footage.

Quality, compatibility, and limitations

Conversion from H.264 to DivX is a second lossy encode, so retain the original ISMV and expect some quality loss. Lower values of FFmpeg's -q:v setting produce higher quality and larger files; test the result on the target device rather than relying only on the filename.

Older DivX hardware commonly expects AVI, MPEG-4 Part 2 video, MP3 audio, standard frame dimensions, and moderate resolutions. It may reject high-definition dimensions, unusual frame rates, variable audio formats, multiple audio tracks, or an AVI file whose extension is .divx but whose streams do not use DivX-compatible codecs. Rename the output to output.avi if the device ignores files with the .divx extension.