Free online RM to MTS converter

Older RealMedia clips often need conversion because current video editors, AVCHD camcorders, and hardware players commonly expect MPEG transport streams rather than RM files. Converting them to MTS creates a file that can be imported into software supporting H.264 video and MPEG transport stream containers.

What the RM format is

RM is the RealMedia container developed by RealNetworks for streaming and storing compressed audio and video. It commonly contains RealVideo and RealAudio streams and was created by RealPlayer, RealProducer, and older RealNetworks publishing tools. RM files are frequently found in archived web videos, legacy educational media, and downloads from the early streaming-video era.

What the MTS format is

MTS is a filename extension for an MPEG transport stream, commonly used by AVCHD camcorders and Blu-ray-related workflows. Typical MTS files contain H.264/AVC video with AC-3 or LPCM audio. The format supports transport-stream features such as packetized multiplexing and is accepted by many video editors, disc-authoring applications, and AVCHD-compatible devices.

How to actually convert RM to MTS

FFmpeg is the most practical desktop tool when its build includes RealMedia demuxing and RealVideo decoding.

1. Install FFmpeg and verify that the input is readable with ffprobe input.rm.
2. Convert the first video and audio streams with re-encoding:

ffmpeg -i input.rm -map 0:v:0 -map 0:a:0? -c:v libx264 -preset medium -crf 20 -c:a ac3 -b:a 192k -f mpegts output.mts

-c:v libx264 converts RealVideo to H.264, while -c:a ac3 produces audio commonly accepted in AVCHD-style MTS files. Lower the CRF value for higher quality and a larger file; values around 18–23 are typical. If the source contains subtitles or extra streams, add specific -map options rather than copying every stream.

On Windows or macOS, a graphical FFmpeg-based converter can expose the same settings: choose the RM file, set the container to MPEG-TS or MTS, select H.264 for video and AC-3 or AAC for audio, then export. For conversion online, the built-in converter at 101convert.com can process the file without installing software.

Quality, compatibility, and limitations

Because RealVideo and H.264 normally use different codecs, this conversion is a re-encode; it cannot restore detail already lost in the RM source. Use the source resolution and frame rate unless the target device requires a specific AVCHD profile. An .mts extension alone does not guarantee full AVCHD compatibility: some devices require H.264 level, bitrate, resolution, frame-rate, and AC-3 settings within a narrow range.

Some very old RM files use proprietary or obsolete RealVideo variants that the installed FFmpeg build cannot decode. If ffprobe reports an unsupported codec, try a current FFmpeg build; DRM-protected or damaged RealMedia files may remain unconvertible.