Free online ISMV to 3GP converter

What the ISMV format is

ISMV is a fragmented MPEG-4 container used by Microsoft Smooth Streaming. Microsoft IIS Media Services and Microsoft Expression Encoder commonly produced .ismv files as video fragments for adaptive HTTP streaming; related audio fragments may use .isma.

An ISMV file can contain H.264 or other MPEG-4 video and AAC audio, but its fragmented structure and streaming metadata are not supported by every media player or editor. Files are often found in Smooth Streaming output folders, server-side publishing directories, or downloaded streaming assets.

What the 3GP format is

3GP is a multimedia container designed for 3G mobile networks and older phones. It commonly stores H.263 or MPEG-4 Part 2 video with AMR-NB audio, although many modern 3GP files use H.264 and AAC.

Its small dimensions, modest bitrate requirements, and broad support on older mobile hardware make it suitable for legacy phones, basic embedded players, and systems that reject MP4 or fragmented MP4 files. The format is not ideal when you need high resolution or preservation-quality video.

How to convert ISMV to 3GP

FFmpeg is the most reliable desktop option because it can read fragmented MP4 media and explicitly set codecs, resolution, frame rate, and bitrate.

1. Install a current FFmpeg build and place the ISMV file in an accessible folder.
2. Convert it to a broadly compatible 3GP file with H.264 video and AAC audio:

ffmpeg -i input.ismv -map 0:v:0 -map 0:a:0? -c:v libx264 -profile:v baseline -level 3.0 -pix_fmt yuv420p -vf "scale=320:-2" -r 15 -b:v 400k -c:a aac -ar 8000 -b:a 64k -movflags +faststart output.3gp

The -map 0:a:0? option keeps the conversion working when the source has no audio track. Change input.ismv and output.3gp to the actual filenames. Use a smaller scale such as 176:-2 and a lower video bitrate for very old phones.

For devices that specifically require H.263 video and AMR-NB audio, check encoder availability with ffmpeg -encoders, then use:

ffmpeg -i input.ismv -map 0:v:0 -map 0:a:0? -c:v h263 -s 176x144 -r 15 -b:v 192k -c:a libopencore_amrnb -ar 8000 -b:a 12.2k output.3gp

The AMR encoder may not be included in every FFmpeg build. If FFmpeg cannot identify the ISMV container directly, first remux it without re-encoding, then convert the resulting file:

ffmpeg -i input.ismv -c copy intermediate.mp4

ffmpeg -i intermediate.mp4 -c:v libx264 -profile:v baseline -pix_fmt yuv420p -c:a aac -ar 8000 -b:a 64k output.3gp

Convert online

You can convert the file for free on the 101convert.com website without installing software. Uploading may be unsuitable for confidential footage or very large files, and the available output settings may not match a particular legacy phone.

Quality and compatibility limitations

Conversion from a streaming fragment to 3GP normally requires re-encoding, so lowering resolution and bitrate reduces file size but also removes detail. Match the target device rather than retaining the ISMV dimensions: older phones often expect 176×144 or 320×240 video, low frame rates, and AMR-NB audio.

Some ISMV files are encrypted, incomplete, or dependent on separate manifest and audio fragments. FFmpeg cannot convert DRM-protected content without the required decryption method, and a video-only ISMV cannot produce audio in the 3GP output. Inspect the source streams with ffprobe input.ismv before choosing codecs.