Analysis: Freeview Sydney Post-Launch of ABC HD (6-7th Dec 2016)

Yesterday marked the launch of ABC HD, which finally means that Sydney Freeview gets each broadcasters’ main stations in high definition at long last. (EDIT: Actually, not quite true, as 7HD Sydney is still a simulcast of 7mate.) According to the launch material, the broadcast would be made in MPEG-4, but of course naturally people did ask me to analyze the service.

Around this time last year was when I last did a comprehensive check of Freeview transmissions, and since then, much has happened which has been captured (at least partially) through interim postings such as these. It gets a little messy to comb through them all, so instead of issuing an interim Freeview Update, I’ve decided to redo the analysis entirely to take another yearly snapshot.

As a result, I am awake at 4am … writing this post. No kidding.

Methodology

As most, if not all stations have moved to statistical multiplexing, spot bitrates can vary wildly. As a result, I take a transport stream recording of the whole multiplex for a period of 3 hours (+/- 1 minute) to average out the bitrates with. The recorded TS files are checked for time, and the bitrates are determined by dividing the size of the demultiplexed PID streams versus the record time. Due to slight inaccuracies in determining record times, total multiplex bitrate is likely to vary by a few kbit/s, but each PID stream bitrate should still be accurate to at least the kbit/s level. The streams were analyzed using TSReader.

Results

freeview-services-table-syd-dec-2016v2

The service summary table is shown above. As I haven’t kept my eye on Freeview for a while, a few changes have happened:

  • RACING.COM channel’s audio bitrate has gone down from 64kbit/s to 48kbit/s.
  • SBS has stopped using 704x576i and 1440x1080i formats and has reverted to the full-size frame formats. Joint-stereo audio has reverted to full stereo coding, and SBS TWO has been renamed to SBS VICELAND. A private stream has been allocated to Food Network where formerly it was sharing with another channel.
  • TEN HD has moved up to High@L4 profile from previously using Main@L4, which should bring more compression efficiency.
  • ABC’s launch of ABC HD using MPEG-4 H.264 High@L4 with a frame size of 1920x1080i, along with Dolby AC3 2-ch audio at 384kbit/s. The News24 service reverts to standard definition with MPEG-2 video and MPEG-1 audio.
  • These changes mean that all HD services are now 1920x1080i at 25fps. No more 50fps services are on the air. Furthermore, all channels except SBS HD have standardized on High@L4 profile.

In regards to channel video bitrate, here is the ranking, sorted by bitrate from high to low:

freeview-service-vid-br-dec-2016

The three shopping channels (in purple) that still are on the air still consume around 1.7-2.3Mbit/s video bitrate. Unfortunately, when it comes to services you’d like to watch, their bitrates are starting to look less healthy.

SBS HD (in red) is the outright leader on absolute bitrate, but this is because it is still using the older MPEG-2 encoding. This allows for older HD sets to still receive HD, but the price is about half the bitrate efficiency of MPEG-4. Even then, it should compete fairly well with the majority of MPEG-4 HD stations based on the fact its bitrate is almost double.

MPEG-4 services (in green) vary somewhat with respect to bitrate. 7HD and TEN HD both have more generous bitrate allocations, especially compared to 9HD. ABC HD has barely the same bitrate allocation as many standard definition channels. This may change in the future, as at this point, the launch of ABC HD is relatively underwhelming with all the content I’ve seen being merely upscaled SD content.

Looking at individual broadcasters, it seems that Channel 7’s push towards HD leaves its standard definition version relatively strangled with just 2.8Mbit/s of bitrate, and 7 TWO isn’t looking that well with 2.5Mbit/s which is only the same as RACING.COM also carried by Channel 7 but in MPEG-4. The 7flix service fares slightly better with 2.9Mbit/s. The only Channel 7 SD service that has a decent bitrate is 7mate raking in 3.7Mbit/s.

In the case of Ten, the services show more healthy bitrates overall. Channel 9 seems to continue to prioritise and balance the SD service with the HD service a lot better, so that SD viewers aren’t seeing a poor picture, although their secondary services have less bitrate.

In fact, it seems that SBS is the one that is really feeling the pinch, due to their all MPEG-2 services, their channels are towards the lower end of the bitrate spectrum. Food Network is their highest bitrate channel outside of their HD service, and VICELAND is even below RACING.COM and only just slightly ahead of the best shopping channel. This is somewhat disappointing to see.

ABC seems to continue broadcasting a good primary SD service, and their ABC2/KIDS is the highest bitrate SD service at the time of survey. Their other services (ME and News 24) both rank fairly well. It seems their HD service has a more “SD-like” bitrate for this balance to occur.

Overall, it seems that standard definition viewers are feeling the bitrate pinch. Where previously the primary standard definition channels may have carried 4-5Mbit/s of bitrate, the increasing pressure of new channels, the need for MPEG-2 simulcasting and the carriage of “non-essential” channels has resulted in the average SD service video bitrate getting closer to 3Mbit/s.

abc-mux-brevo

A closer look at the ABC multiplex bitrate evolution shows that for the most part, the ABC2/KIDS service has seen a slow increase in rates, the ABC3/ABC ME service a slow decrease in rates, and the main SD channel has been holding fairly stable although trending towards a slight reduction. News 24 took a major cut and went back to SD to allow for the launch of ABC HD.

freeview-per-pid-rates-syd-dec-2016

Looking at the per-PID rates, it seems that ABC HD may indeed pick up more bitrate in the order of up to 1Mbit/s as the multiplex has a lot of nulls compared with most other broadcasters. On the whole, mux utilization for all broadcasters was aggressive with the exception of ABC (1.3Mbit/s free) and Seven (0.6Mbit/s free, twice as much as the others). Due to an improvement in determining the recording time, the reported mux bitrates are now much closer – slight variations are likely due to packet loss due to transient reception errors.

Conclusion

The launch of new HD services is a double-edged sword. On the one hand, for those with more modern sets or computer tuners, we are able to enjoy full HD at long last, using the more modern H.264 AVC MPEG-4 codec. However, the need to keep compatibility with legacy receivers capable of only MPEG-2 video and MPEG-1 audio really means that we are still losing some bitrate there. In some cases where the former HD station was not a simulcast, this also meant “splitting” the bitrate from a former MPEG-2 HD service into an MPEG-2 SD service and an MPEG-4 HD service, resulting in more bitrate constraints on both services.

As a result of the aggressive move by all broadcasters (except SBS) to embrace the MPEG-4 encoding, the HD services are able to look acceptable despite using only marginally more bitrate than a regular SD service. The bias towards the HD service is apparent for 7HD and TEN HD, whereas Nine and ABC are both prioritising their SD services instead.

The failure of SBS to transition to MPEG-4 at this time has resulted in their other SD MPEG-2 services being bitrate starved compared to the competition, and overall, bitrates across the board for standard definition services predominantly lie in the 3Mbit/s region where several years back they would have been closer to 4-5Mbit/s. This is not of great relevance where users are watching the HD primary service, however, will affect all users of secondary services carried by the broadcaster. The number of shopping channels is less than in prior analyses, but their existence only exacerbates the bitrate-limited nature of DVB-T broadcast.

The launch of ABC HD itself is a good thing, but at this stage as many viewers have noted, is rather underwhelming due to the broadcast of only upscaled SD content at most times. The service does have about 1Mbit/s of wriggle room, so it could turn out to be quite competitive with the commercial broadcasters’ HD channels, but at the time it was surveyed, this was not the case.

Lets hope SBS transitions to MPEG-4 on its HD channel to relieve the bitrate starvation on its SD services – after all, it is already simulcasting HD and SD in MPEG-2, so it’s really only gains.

This is a dreary-eyed Gough, signing off for the day …

Update: Service Bitrate Evolution over Time

At the request of one my regular readers who wanted to see more service bitrate evolution graphs for the other multiplexes, I went on a rampage to gather all of my data to allow it to be plotted. Of note is the fact that I don’t do “global” surveys of bitrates very often and depending on the situation (impending channel launch), will only survey one mux at a time. As a result, the number of samples for each multiplex varies, as do their spacing in time.

Channel 7

Due to the number of changes in Channel 7’s line-up, I have a lot of data samples for them. The graph shows just how rocky the history of bitrates for the channels has been, at least on Channel 7’s mux. The main station has swung wildly, but overall the trend is downward as of late, as is with 7TWO. At one point, their bitrates were lower than necessary as the null packet fraction was quite high due to a potential misconfiguration after turning off a channel. TV4ME has left the air, and RACING.COM has increased its bitrate marginally. It seems 7flix has also gained in its bitrate, and 7mate as well, whereas 7HD has lost out over time. The big drop in 7mate corresponds to the launch of 7HD. The days of SD services having 4-5Mbit/s seem to be well and truly behind us.

SBS

I don’t have much data for SBS, and that is primarily because not much has happened bar for the launch of the Food Network channel. SBS TWO used to command a fair chunk of bitrate, at the expense of SBS HD which did some mode changes from time to time, but has otherwise been restored to its 2013-level of bitrate. The increase in available bits to accommodate the food network was primarily due to a change at the time of launch to their modulation mode to increase available bitrate as their competing channels. All stations now run 1/16th guard interval, with 3/4 code-rate.

Channel 9

Channel Nine’s strategy seems to be relatively conservative. EXTRA 2 got the axe, freeing up 2Mbit/s. Along with the reversion of GEM to SD, this gave the necessary bitrate to support 9Life and 9HD. All services have been very consistent in bitrate allocation at the sample points.

Channel Ten

Ten’s bitrate strategy seems to be a little hill-and-dale. The shopping channel Spree has only drifted downwards marginally, whereas TVSN has sort of gone upwards and levelled out. Ten HD’s bitrate has been relatively stable after the 1Mbit/s “teaser” stage. ONE however, has seen bitrate cuts throughout its high definition life to feed the bitrate increases to TVSN and ELEVEN. However, on the launch of the HD service, the boost to ELEVEN had been cut back noticeably, and the main standard definition channel received its first bitrate cut. This results in all the non-shopping standard definition channels sitting at roughly the same bitrate of 3-ish Mbit/s.

ABC

I covered it earlier, but since I found one more data-point, I’ve decided to produce an updated graph. It seems that bitrate movement at the ABC is gradual. The main SD channel has only received a marginal cut to bitrates, with News24 making a big drop as it reverted from HD to SD. ABC2/KIDS had undergone a fairly consistent ramp-up in bitrates, whereas ABC3/ABC ME has trended downwards over time.

TVS

I decided to include this particular graph of the now-defunct TVS just for a laugh. Not given the pressures of bitrate budgeting between competing services, its bitrate has been rock-solid right up until it went off the air.

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6 Responses to Analysis: Freeview Sydney Post-Launch of ABC HD (6-7th Dec 2016)

  1. Old Techo says:

    G’day Gough,

    Thanks once again for great info. I have a 10 year old Onkyo AV Receiver and it correctly displays and plays Dolby on Ten HD (Ch 13 Melb) and Nine HD (Ch 90 Melb) however it won’t recognise/play Dolby on either the new ABC Ch 20 or SBS (Ch 30 Melb) despite both claiming Dolby.

    Are there varying audio modulation techniques (as with contemporary video) that my oldish Onkyo cannot decode?

    Regards,

    Trev

    • lui_gough says:

      Dear Trev,

      I’m not sure how your setup goes, or indeed what the multiplex in Melbourne looks like at the moment, but on the whole, Dolby AC3 is pretty much the same stuff channel to channel. They all use the “regular” complete main mode of encoding which should be compatible with all Dolby AC3-capable receivers, so the reason why you’re not getting audio is a bit of a mystery which may come down to the finer details. For reference, SBS in Sydney does not transmit any Dolby at all, and if you’re getting a picture, you’re getting the digital data out of the multiplex just fine, so it’s probably down to how the receiver handles subtle metadata or encoder differences.

      I’m going to assume that you have some sort of set-top box that’s receiving the station and outputting the data to your receiver via a TOSLINK optical connection or similar. In that case, what may be sabotaging you may be the set top box itself not outputting the bitstream correctly. If this is the case, there’s not much you can do aside from (maybe) looking for a firmware update which may help (or make things worse).

      I looked into the stream information from TSReader about the AC3 streams – they are dumped below:
      7HD Sydney
      Elementary Stream PID 579 (0x0243) Dolby AC3 Audio
      AC3: Bitrate 384 Kbps Sample Rate 48 KHz
      AC3: Mode complete main Coding 2/0 L, R
      AC3: Dolby Surround Mode not indicated
      AC3: LFE Mode Off Dialogue normalization -24 dB
      Descriptor: AC3 Audio Descriptor
      Flags: AC3 Type: True BSID: True Main ID: True ASVC: False
      AC3 Type: 66
      BSID: 6
      Main ID: 1
      Descriptor: ISO639 Language Descriptor
      Language: eng
      Audio type: undefined

      Nine HD
      Elementary Stream PID 650 (0x028a) Dolby AC3 Audio
      AC3: Bitrate 448 Kbps Sample Rate 48 KHz
      AC3: Mode complete main Coding 3/2 5 L, C, R, SL, SR
      AC3: Center Mix Level -3.0 dB Surround Mix Level -3.0 dB
      AC3: LFE Mode On Dialogue normalization -24 dB
      Descriptor: AC3 Audio Descriptor
      Flags: AC3 Type: True BSID: True Main ID: False ASVC: False
      AC3 Type: 66
      BSID: 8
      Descriptor: ISO639 Language Descriptor
      Language: eng
      Audio type: undefined
      Descriptor: Stream Identifier Descriptor
      02 .
      Descriptor: Registration Descriptor
      Format identifier: 0x41432d33 (AC-3)
      Descriptor: Maximum Bitrate Descriptor
      Maximum bitrate: 57600 bytes per second

      TEN HD
      Elementary Stream PID 649 (0x0289) Dolby AC3 Audio
      AC3: Bitrate 448 Kbps Sample Rate 48 KHz
      AC3: Mode complete main Coding 3/2 5 L, C, R, SL, SR
      AC3: Center Mix Level -3.0 dB Surround Mix Level -3.0 dB
      AC3: LFE Mode On Dialogue normalization -24 dB
      Descriptor: Stream Identifier Descriptor
      02 .
      Descriptor: ISO639 Language Descriptor
      Language: eng
      Audio type: undefined
      Descriptor: Registration Descriptor
      Format identifier: 0x41432d33 (AC-3)
      Descriptor: AC3 Audio Descriptor
      Flags: AC3 Type: True BSID: True Main ID: True ASVC: True
      AC3 Type: 66
      BSID: 8
      Main ID: 0
      ASVC: 0
      Descriptor: User Private Descriptor: 0x81
      08 3c 05 .<. Descriptor: Maximum Bitrate Descriptor Maximum bitrate: 57400 bytes per second ABC HD Elementary Stream PID 2321 (0x0911) Dolby AC3 Audio AC3: Bitrate 384 Kbps Sample Rate 48 KHz AC3: Mode complete main Coding 2/0 L, R AC3: Dolby Surround Mode not indicated AC3: LFE Mode Off Dialogue normalization -24 dB Descriptor: Stream Identifier Descriptor 02 . Descriptor: Maximum Bitrate Descriptor Maximum bitrate: 51350 bytes per second Descriptor: AC3 Audio Descriptor Flags: AC3 Type: True BSID: True Main ID: True ASVC: False AC3 Type: 66 BSID: 6 Main ID: 0 Descriptor: ISO639 Language Descriptor Language: eng Audio type: undefined On the whole, there are some subtle differences in the flagging, namely the BSID, Main ID and ASVC flags. However, all use Complete Main encoding in either stereo or 5.1 channel surround. Could it be that your receiver is having problems with only stereo Dolby stations as Ten and Nine are both 5.1 channel surround? Maybe there are some bugs in your decoder, or expectations that it's receiving a 5.1 stream only. Maybe checking the specs on the decoder manual itself might help. Sincerely, Gough

      • Old Techo says:

        Gough, thanks for your prompt reply 🙂

        As an aging Tech I am a bit out of my depth with digital modulation techniques.

        Further info that may help… my setup is a few months old Samsung 65″ TV HDMI coupled to my Onkyo. The TV audio options include Dolby selection (done) and either PCM or Bitstream. I have tried both with the same result.

        The TV ‘info’ display tells me video and audio specs. This is how I know that the HD channels of Ten, Nine, SBS, ABC and Seven are all Dolby.

        So confirming of the above 5 HD Dolby channels only Ten and Nine work via my Onkyo. The other 3 appear as several various options of non-Dolby audio according to the Onkyo display.

        Regards,

        Trev

        • lui_gough says:

          Dear Trev,

          Assuming that your Onkyo receiver is capable of Dolby decoding, Bitstream is the most appropriate option as that passes through the data stream as transmitted, letting the receiver decode it. I’m not sure what the Dolby selection does, but PCM basically means your TV does the decoding and sends the raw audio to the receiver, often just 2-channel stereo. Dolby could indicate the TV does some transcoding of the audio – I’m not sure.

          If on Bitstream, your receiver is “none the wiser” as to what audio mode is in use, sadly, it sounds like the receiver just can’t handle stereo Dolby AC3, and only seems to decode the channels that send 5.1 channel surround Dolby AC3.

          – Gough

  2. Steve says:

    Confused about the opening paragraph. Last time I checked 7 HD in Sydney is still a simulcast of 7Mate rather than 7 proper due to the AFL in HD commitments?

    • lui_gough says:

      As noted by another commenter previously – yes 7HD Sydney is still a simulcast of 7Mate at this stage, which should change … sometime …

      Edit made to avoid confusion – it’s what happens when I rush out an article at 4am in the morning – brain’s not fully functioning.

      – Gough

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