How to Convert Video to RealVideo Format with FFmpeg

This article explains the capabilities and limitations of transcoding video to the legacy RealVideo format using FFmpeg. You will learn why direct RealVideo 4 (RV40) encoding is not natively supported in FFmpeg, how to use the available RealVideo 1.0 and 2.0 encoders instead, and the exact command-line syntax required to generate RealMedia (.rm) files.

The RealVideo 4 Limitation in FFmpeg

While FFmpeg is highly versatile, it does not support encoding to RealVideo 4 (RV40) or RealVideo 3 (RV30). The FFmpeg libraries only contain decoders for these proprietary formats.

If you must use FFmpeg to target the RealMedia container, you are limited to encoding with the older, open-source-reverse-engineered RealVideo 1.0 (RV10) and RealVideo 2.0 (RV20) encoders.

How to Encode to RealVideo 2.0 using FFmpeg

To transcode a modern video file into a legacy RealMedia (.rm) container using the RealVideo 2.0 codec and RealAudio 1.0, use the following FFmpeg command:

ffmpeg -i input.mp4 -c:v rv20 -b:v 500k -c:a real_144 -b:a 8k output.rm

Command Breakdown

-i input.mp4: Defines the source video file you want to transcode.
-c:v rv20: Specifies the RealVideo 2.0 encoder. (You can also use rv10 for RealVideo 1.0).
-b:v 500k: Sets the video bitrate to 500 kbps. Adjust this value depending on your desired quality and file size limits.
-c:a real_144: Specifies the RealAudio 1.0 encoder, which is widely compatible with legacy RealMedia containers.
-b:a 8k: Sets the audio bitrate. The real_144 encoder is highly limited and generally requires a fixed bitrate of 8k (8000 bps).
output.rm: The output file path using the RealMedia extension.

Alternative for True RealVideo 4 Encoding

If your project strictly requires the RealVideo 4 codec (often associated with RealPlayer 9 and 10), you cannot use FFmpeg. You must instead obtain a legacy, proprietary tool such as Helix Producer (formerly RealProducer) or the Helix DNA Producer command-line tool. These original SDKs contain the official, proprietary RealNetworks libraries required to compress video streams into the RV40 format.