It depends on the bitrate. At about 96 kbps or 128 kbps and above, AAC-LC with a sampling rate of 44.1 kHz gives the best results.
For bitrate-limited environments, AAC-HE v1 introduces spectral band replication (SBR), and should be used down to about 48 kbps or 64 kbps. SBR means that the true sampling rate of the audio is only 22 kHz due to the limited bitrate (as opposed to the 44.1 kHz of CD audio) and that anything above ~11 kHz in the audio spectrum is extrapolated (i.e. the high frequencies are guessed based on the harmonics of the lower frequencies).
For very bitrate-limited environments (below ~48kbps), AAC-HE v2 adds parametric stereo (PS) in addition to the SBR. Now the true audio file is not only 22 kHz sampling, but also mono, and the stereo information is also essentially extrapolated as well. About 2 or 3 kbps of the audio stream is dedicated to telling the decoder whether to pan the mono audio to the left or to the right to give the impression of a stereo source, but there aren’t actually two discrete audio channels.
AAC-HE is effectively a set of enhancements to fake it where there isn’t enough bitrate to use AAC-LC with a true 44.1 kHz sampling rate and/or stereo. For me, anything that’s encoded in AAC-HE I can usually immediately tell because the trebles sound artificial and tinny since they’re essentially just guesses at what the treble should be.
Note: To get the frequency response from sampling rate, divide by two (e.g. a 44.1 kHz sampling rate gives you a frequency response of up to about 22 kHz, whereas a 22 kHz sampling rate gives you response up to about 11 kHz). Human hearing goes up to about 20 kHz. Using AAC-HE at higher bitrates would actually sound worse than AAC-LC since AAC-HE discards the upper half of the audible frequency range and extrapolates it instead.
Note 2: The bitrates I’m referring to refer to the actual audio bitrate. The bitrates reported on DAB+ also include other elements of the stream (e.g. slide show, text, etc.) and the true audio bitrate is lower than what is reported.
Getting back to the new Gold Coast consultation paper for the proposed ERP of 25KW DA. I have generated some coverage maps to get an idea of the proposed coverage using the Nautel Coverage map tool.
The first one is for 25KW over azimuth bearings 25’-180’ please note that the coverage tool only produces omnidirectional coverage maps, so please disregard coverage in other directions.
It shows some overspill from the Gold Coast into the Brisbane market, so it looks like there will be dxing possibilities, more so in Brisbane then in Sydney from the following coverage maps.
@SydneyCityTV@TV-Expert@Radiohead discussed the possibilities of DAB+ dxing opportunities in Sydney from Wollongong and the Central Coast. As no draft DAB+ plan has been produced for these markets I have had to use the DAB+ planning principles, and antenna documents.
Wollongong is to be 5KW and 3.75KW towards Sydney based on the proposed antenna design.
Overspill from Brokers Nose into Sydney will be strictly coastal from Cronulla to Bondi Junction with the strongest signal around Malabar to Maroubra. Bondi Junction will fall in the mush zone of Wollongong and the Central Coast.
The planning principle only states 3KW for Gosford DAB+ and I estimate from the proposed antenna design 2.25KW towards Sydney.
Overspill from Gosford into Sydney will be strictly northern beaches, upper north shore and around Dural, and some coverage around Bondi Junction which will produce the mush zone according to these maps.
Coastal tropo from the north and south will cause massive issues for out of area coverage and possibly within the licenced coverage areas of Gosford and Wollongong.
I do notice 2UE does not sound as good now (worse than it should be) it has been cut back to 72K and this maybe the reason why. They should flick it too AAC-HE v1 ?
I still feel ripped off when 2UE said it was moving to “improve the quality of audio”. Hahah first world issue.
Of course we’ll just have to see what happens, but personally it wouldn’t overly surprise me if SEN have bought 64kbps from Nine Radio and that they’ll be using it at some point - likely after 2CH becomes a digital only station and the company will have at least five (SEN 1170, SEN Victoria, SENTrack, Niche Radio & 2CH) stations on Sydney DAB+. What other explanation could there be for Nine Radio only using 192kbps of 256kbps?!
Have SEN said for sure SEN Vic would be carried as well as the main SEN? Surely it’s not worth them paying lots of cash to Nine for their DAB space just for a niche station that might cannibalise listeners to their main SEN.
I also can’t see Nine giving a leg up to their still competitor - 2GB’s sports content still competes with SEN.
I think I found the reason why the bit drop, it may not be true they are donating or sharing the bits, they are just making signal more “robust”. 2UE / 2GB / NTS are now 2-A EEP, thus the less bits. I should have tested whilst on the road trip if it makes a difference. For our folk outside of Sydney do you find 2ue has less dropouts than the rest?
Put 2CH in the car and see how it affect the reception. In general with the Kia its ok. It does break up in spots you wouldn’t expect like Thompson corner. It is only a split second. My guess it is interference. With 4A I think those cheap radio would suffer the most. I am really in two minds. Probably at my location I prefer more bits so I can put up with the 4A .
