The Helix project is supported by RealNetworks, which uses the code produced by the project in its proprietary apps, including the RealPlayer media player. Helix Player is the open source media player from the project, and is based on the Helix Client, which, as per RealNetworks, has been shipped in some 350 million mobile phones.
Despite its reach, Helix Player can play only a limited number of media formats. According to its documentation, Helix Player will play an HTTP stream, but that doesn't seem to work in this version. It supports Real's RAM and RPM playlist formats, and will also play their RTSP streams.
LIMITED PLAYBACK: RealPlayer for Linux is still an underprivileged version of its Windows cousin
Helix has support for the H.263 codec used in Flash videos, but it couldn't play FLVs from YouTube, AVI, MPEG, MP3, or DVD. The one format it can play without any issues is OGG. RealPlayer for Linux fares a little better. It supports all the formats that Helix can handle, and also plays MP4, Flash Video, WMV9 and different versions of RealVideo, though it still can't handle AVI, MPEG, or DVD.
Both Helix and RealPlayer enable you to install a browser plugin during installation, and both support playlists. They also have the same configuration options, and there's a number of things to tinker with, such as adjusting the processing power used for playback.
The main goal of both players is to play streams from Real's SuperPass streaming service. However, they're missing features you'll find in a general purpose media player, such as video post-processing, and are further depreciated since many other players can use Real's proprietary formats.
Version: Helix/RealPlayer 11 Gold.1.1
Price: Free under GPL and other licensing
Both players go beyond RealMedia content, but only barely.