FMeXtra

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FMeXtra is an in-band on-channel digital radio broadcasting technology created by Digital Radio Express. Unlike iBiquity's HD Radio system, it uses any FM radio station's existing equipment and transmitter plant to transmit digital audio data on subcarriers instead of sidebands. It also requires no royalties for its use, which run thousands of dollars per year for HD Radio.

The system is run from a single rack unit box called the X1 Encoder, which is actually based upon a personal computer server and digital audio hardware from Lynx Studio Technologies (LST). Control is entirely via software, via gigabit Ethernet, USB, serial port, and SVGA video monitor. All processing is handled internally by a Pentium 4 running Windows XP.

FMeXtra is fully compatible with HD Radio hybrid mode, which uses additional radio spectrum beyond the ±100 kHz signal. It is not compatible with HD Radio in all-digital mode, however this is not expected to be used for a very long time, given that there are already billions of analog FM radios already in use. It is also not compatible with all existing subcarriers. Thus, a public radio station might have to remove its radio reading service for the blind, and replace it (and its dependent listeners' receivers) with a digital one. This would take up much less bandwidth, particularly since voice can be highly compressed, however the changeover could be somewhat disruptive. The signal is partitioned so that RBDS, stereo, or other existing subcarriers can be protected, at the expense of bandwidth.

The codecs used are AAC and aacPlus v1 and v2, at bitrates of 8 to 384kbit/s, and sample rates of 8 to 96 kHz, for anywhere from monophonic to 7.1-channel surround sound. Multiple audio programs as well as limited multimedia can also be broadcast, as with HD Radio.