Considering Seven have an extra channel in Racing.com, it was the best way to retain better picture quality across their suite of channels.
[quote=“Firetorch, post:290, topic:279”]and when there is a drastic change in technology, this should be prepared and advertised MANY years in advance. As it was when digital television first arrived.
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It is unrealistic to expect over a year of “advertising” - especially in this day and age - considering you continue to get 99% of the content you got before. The only thing that will come close to the changeover analogue to digital will be when the remaining channels changeover to MPEG-4 which’ll be a few years from now.
DVB-T2 also increases the total bitrate bandwidth. We could see up to 35 Mbits on a single mux, combined with better compression of MPEG-4 services than DVB-T offers, too! You could probably squeeze all 3 commercial network’s services on a single DVB-T2 mux if they’re all using MPEG-4 encapsulation.
MPEG-4 reduces the amount of data that needs to be transmitted (i.e. bitrate) whereas DVB-T2 increases the amount bandwidth available. If you combine the two, then you get a double benefit. In the UK, the DVB-T2 multiplexes give about 40 Mbps of bandwidth, compared to about 24 Mbps for DVB-T (they use slightly wider 8 MHz channels, compared to our 7 MHz).
Given 9HD’s birates (around 3.5 Mbps), you could fit around 10 MPEG-4 HD channels on a single DVB-T2 mux.
Another problem with DVB-T2 is that there would ordinarily have to be a simulcast period with DVB-T to allow consumers time to upgrade their equipment (similar to what we had with analogue and digital TV changeover).
But the way it stands now is that there is NO spare spectrum.
The only alternative is for the Government to mandate a nation wide straight switch to DVB-T2 on say 1 January 2021, AND say that ALL Digital TVs/receivers etc sold in Australia must be DVB-T2 capable by say 1 January 2017. So anyone who has not updated by 2021 would be left with NO TV reception at all.
There’s the sixth channel in all areas (though only one in places like the Gold Coast where there are two sets of commercial networks) that isn’t used, so would be a spot to put a trial of DVB-T2, ideally using HEVC.
The community TV channels use the sixth channel of different blocks, but even with the extension, they still only have until the end of this year, which would free the sixth channel in all areas, though in the short term you wouldn’t expect a full regional rollout anyway.
The other option is combining SBS and ABC on one multiplex, and using the spare one created in DVB-T2 mode.
Then you’d just both add new services and HD simulcasts of existing ones and eventually start removing services from DVB-T, until you’re left with one multiplex in DVB-T carrying the main channels in MPEG-2 SD, and three multiplexes in DVB-T2. Leaving two empty to have a second digital dividend, or three if the costs of subsiding receiver replacement for the holdouts is worth it.
The likelihood of it happening depends entirely on whether the government sees the phone carriers here as being in a position to want even more bandwidth, or if they think phasing out 3G will be enough before OTA TV dies a natural death at the hands of the internet.
This table shows that at the same level of perceived image quality, HEVC has an approximate 62% bitrate savings over MPEG-4 at 1080p. So say we reduce the bitrate of the current MPEG-4 HD transmissions by 60% to about 1.5 Mbps by adopting HEVC, while at the same time adopting DVB-T2 (giving say around 40 Mbps per mux), this would allow about 25 HD channels in a single mux. Essentially, this would mean all of the current broadcasts (over 5 muxes using DVB-T) would fit in one HEVC DVB-T2 mux.
As Moe mentioned, there’s a sixth frequency allocation free in every area. This could be used for HEVC DVB-T2 during a simulcast period whilst DVB-T is gradually wound down. After the simulcast, all you’d need is one HEVC DVB-T2 mux in each area (able to carry about 25 1080p HD channels).
You’d think the government would love this option, given once the transition is complete, it would free up 25 7 Mhz channels (175 MHz of spectrum) for auction. The benefits would be all the channels in 1080p HD + more bandwidth for mobile broadband; the negative is the cost of the hardware upgrades required (both on the broadcasting and consumer side).
I don’t think 1.5 is a realistic bitrate. In UK for example I think that the DVDT2 broadcasts average somewhere between 4.3 to 4.9 per HD channel. Perhaps a slightly lower rate could be chosen here for all or perhaps just some of the channels for better spectrum use
The UK’s DVB-T2 HD broadcasts are using H264 MPEG-4 though. I’m talking about HEVC (H265), which supposedly requires only about 40% of the bitrate that H264 requires.
Edit: I encoded some 1080p test footage into HEVC at an even lower 1 Mbps and it looks quite reasonable; so I think 1.5 Mbps 1080p in HEVC would be do-able.
I thought the government had “intentions” of allocating this 6th channel to a new broadcaster, which is part of the reason why community TV is being asked to move online?
Whether this happens or not, time will tell, but yes, DVB-T2 and H265 would be an interesting prospect.
Page 2 of this shows the government’s short-tem intentions for the 6th channel after CTV is taken off air – “to test and migrate to new and more efficient broadcasting technologies”:
