Freeview HD is now being beamed from the Winter Hill transmitter group in the North West and the Crystal Palace group in London following the world-first adoption of the DVB-T2 standard and MPEG-4.
During a briefing at the BBC Media Centre, BBC head of broadcast infrastructure James Jackson demonstrated live HD transmissions on digital terrestrial television.
Using brand new IDTVs manufactured by Panasonic and Sony, Jackson showed afternoon promos of BBC HD and ITV HD coming live from Crystal Palace and Winter Hill.
Jackson also showed Freeview HD on set-top-boxes manufactured by Pace and Vestel, although he stressed that all the products are still in the testing phase at the Digital TV Group.
Both HD channels were incorporated into the Freeview EPG with all existing standard definition offerings. Freeview will also now introduce its branding onto the EPG to remind viewers what they are watching, even when using third-party services, such as IP Vision.
BBC HD is the same service as currently available on Freesat, but ITV HD is a new upscaled simulcast of the ITV1 channel. ITV has also pledged to broadcast the majority of its peak-time schedule in native HD on Freeview.
Channel 4 HD will arrive on Freeview next year and the service is expected to have five HD channels available by 2012.
Jackson said that today's launch has brought Freeview HD to 23% of the UK, which will grow to 40% next year when a series of advanced networks in key metropolitan areas come online.
The BBC has set a target of 50% coverage in time for the 2010 World Cup tournament in South Africa, and Freeview HD will reach full 98.5% UK coverage by the end of 2012. Click here to view the full launch schedule.
Set-top-boxes, IDTVs and PVRs supporting Freeview HD will start reaching retail outlets during the first quarter of 2010, backed by a major marketing campaign.
Freeview is also currently testing a coverage check database for users to input their postcode and receive information about when they will get access to Freeview HD and what equipment they will need to watch it.
After praising the launch of HD on DTT, Freeview managing director Ilse Howling said that the "next step is to go from digital TV to IPTV", hinting that a Project Canvas-enabled Freeview HD box is next on the agenda.