Freeview Update: Channel 7’s Multiplex after the launch of 7flix

7flix-logo

Today marks the official launch of 7flix, Channel 7’s new movie-oriented channel. Since the channel is now running actual content, the configuration of the encoders should have reached their “production ready” state, so lets see where the chips have landed.

Results

The transport stream was recorded over a period of over one hour to derive the following information.

ch7-postflix-svc-summ

From observations of the services, it seems several changes have been made since the last observation. The main Channel 7 station has reverted to stereo encoding rather than joint-stereo, and TV4ME has reverted to a slightly higher horizontal resolution of 528x576i after being at 480x576i for a short while. This could be because some TVs displayed the wrong aspect ratio for the 480x576i stream or because the quality was not sufficient. As I had predicted, 7flix retains the same encoding type as in the loop-days, but now has a closed-captioning text PID to allow for subtitling to be broadcast, and also has a HBBTV private stream for Smart TV usage.

ch7-postflix-bitrate-evo

In terms of the bitrate evolution, it seems that 7Digital has edged up a hair, but 7TWO and 7MATE have both lost bitrate to prop up 7flix. As I had predicted, there was no way for 7flix to run decent video on as low as 800kbit/s, so now it’s actually running at about 3Mbit/s which is quite a high bitrate for an H.264 encoded SD service. The remaining bitrate contribution is made up by reducing the crazy 1.2Mbit/s of null packets to just under half of this, also as I had predicted. However, watching it on my TV still shows signs of posterization and overly smooth areas, which may be a result of using live encoders which are not as efficient as offline encoders. Both TV4ME and RACING.COM retains the same bitrate.

ch7-postflix-per-pid-bitrate

This is borne out by looking at the raw PID-rates table.

aggressive-statmux

It seems that stat-muxing is here to stay and is operating aggressively. Even on a short sample recording of the transport stream, it can be seen that bit-rate trading between the main 7 Digital, 7mate and 7flix is occurring, with the other services less affected or already at their fixed limits. As a result, the bitrate analysis is only exact for the period I surveyed the channel, and could vary significantly depending on the programming on the channel. That being said, as my rates are averaged over greater than one hour, it is more representative than an instantaneous spot reading.

If you have trouble …

The results of today’s check on Channel 7’s multiplex will not please all viewers, partly because DVB-T did not standardize on MPEG-4 family of codecs, at least not when many of the older set-top boxes and TVs with integrated tuners were built.

If you still receive the other Channel 7 stations properly, but are having trouble with 7flix, TV4ME and RACING.COM, then you are likely to own an older unit which does not have any support for either MPEG-4 H.264 AVC video or MPEG-4 HE-AACv2 audio.

Your symptoms may include:

  • Black screen with no video or audio indicating your tuner supports neither MPEG-4 audio nor video.
  • Vision with no audio indicating your tuner supports MPEG-4 H.264 video but not MPEG-4 HE-AACv2 audio.
  • Vision with noise as audio indicating your tuner supports MPEG-4 H.264 video but did not identify the audio stream correctly and is decoding it incorrectly, or cannot actually decode MPEG-4 HE-AACv2 audio.

As it seems that they have settled on using these MPEG-4 modes as a necessary evil to ensure their bit-rate budgets and quality of service targets are met, your choices are limited.

  • Check if there are any firmware updates for your particular device, and apply them to see if there is any improvement. Note that if you do this incorrectly, you could permanently brick your device.
  • Purchase a new tuner or TV with MPEG-4 H.264 AVC video and HE-AACv2 audio support, however, this could get expensive and result in you losing out on TV-integrated PVR functions.
  • Use a PC-based TV tuner which returns raw Transport Stream data and uses software codecs to decode the stream – my over 10-year old tuner is running these analyses, so yes, it will still work into the future if they choose to use even newer codecs (e.g. H.265/HEVC) on the air.
  • Remove the channels from your program list or ignore their existence while silently fuming inside. Maybe try telling someone, not that it’s likely that will change anything.

Unfortunately, there seems to be no way to tell in advance whether a particular unit supports HE-AACv2 audio from the outside as it doesn’t seem to be part of the Freeview certification process. It seems like buyers are in a “buy and try” conundrum with this one.

Conclusion

There’s never any free lunch, and with a limited bit-rate budget, instead of launching an HD simulcast station, Channel 7 has decided to launch a movie-oriented channel using purely MPEG-4 codecs while retaining their high definition MPEG-2 based 7mate. This is unique in the Freeview DVB-T system so far where most other broadcasters have not employed any MPEG-4 audio codecs, staying with MPEG-1 and AC3 (which are mandated codecs for Australian DVB-T) likely because of compatibility issues.

Unfortunately, this means that bitrate pressures are high which has resulted in the effective deployment of stat-muxing to counteract this to some extent, but also means that bit-rates overall may have suffered. MPEG-4 was a necessary evil to ensure quality of service of their main channels are affected as little as possible.

Sadly, some people using older/cheaper devices without the MPEG-4 decode ability are seeing nothing, or video with no audio or noise, and will end up missing out on it unless they upgrade to newer devices.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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21 Responses to Freeview Update: Channel 7’s Multiplex after the launch of 7flix

  1. annie says:

    Not happy. Not everyone can afford new TV

  2. Margaret says:

    Looking forward to seeing the film but my screen says “No video”, so I guess I won’t see much – and I am 7k from the heart of Melbourne!!!!!!!!

  3. Stupid move channel 7, what make everyone go out and buy a new tv just for 76flix…you guys suck, I am not going to buy a new tv just for this station, you have failed big time !!!

  4. Unaffordable for Many says:

    What’s really upsetting is that when analog was being switched off – only within the last 3-4 years – the government provided (i.e. taxpayers paid for) tens of thousands of set top boxes for seniors, especially ones on low budgets or who are not tech savvy. That included special read-aloud set-top boxes which can be used by people who are blind, as the only way for many of them to be able to use digital tv. To the best of my knowledge none of those set top boxes can use MPEG4 and the are still the people least able to afford to go buy new equipment to get these new channels.

    • pearty says:

      That’s not true. I have helped a number of people who received the government supplied set top boxes and they ALL support MPEG-4. At least the ones provided in WA do. I have been assisting a group of people in Homeswest accomodation set up and configure their boxes and they all are able to watch 9HD, 74Me, Racing.com and 7Flix. I haven’t had a chance to check whether they can view 10HD but I haven’t received any calls so I assume they can watch that chanel as well.

  5. Lynn says:

    BaBow! Lovely picture.. no sound! Thanks Lui for clearing this up for the tech unsavvy like me. Pretty big fail there Channel 7. No 7flix for this household.

  6. Damon Cox says:

    Speechless and very disappointed by channel 7 not informing that there would be no sound on 7flix unless you go out and spend about $2000.00 on a new tv .another viewer lost 7

  7. paul says:

    Sound but no picture….7flix, TV4ME and RACING.COM….but my tv supports mpeg4 h264???????????????????????????????????????????????????????????????????

  8. Their use of HE-AACv2 is actually quite a compatibility nightmare, and worse still, at the bitrate they’re using it’s actually hurting their audio quality.

    All AAC streams are backwards compatible. HE-AAC works by splitting the frequencies in two — encoding the lower half as a regular AAC-LC stream, and the higher frequencies using SBR. HE-AAC v2 works by going one step further, and encoding the HE-AAC v1 stream in mono — and storing an approximation of the original stereo signal as parametric stereo data.

    The problem is that there are plenty of MPEG-4 capable TVs out there that don’t do HE-AAC v2 — and possibly a few that don’t do HE-AAC at all.

    Decoders that only do HE-AAC v1 end up with a mono audio signal.
    Decoders that only do AAC-LC (which SHOULD be rare…but could be a fallback in case of an unexpected v2 stream) end up with both a mono audio signal and a low quality audio stream at half the sampling rate — 24kHz (=12kHz frequency) instead of 48kHz.

    There are complaints of both of these — but particularly the mono issue — on Whirlpool and Twitter amongst others. And this is also assuming that the backwards compatibility feature actually works and that no HE capable decoders are just choking on v2 and spitting out silence.

    But worst of all — and lest someone beat the “march of progress” drum — HE-AAC v2 simply wasn’t designed for 64kbps. It was designed for ultra low bitrates around the 32-40kbps mark. At 64kbps, the forcing of parametric stereo is actually hurting audio quality, because you’re overallocating bits to a mono stream and collapsing true stereo into PS approximations.

    Simply put — the great compatibility nightmare is all for nothing because Channel 7 engineers don’t know what they’re doing and are actually hurting sound quality rather than going with HE-AAC v1 at 64kbps.

    • lui_gough says:

      I agree with your analysis, and it’s very true that an older decoder without HE / v2 extensions won’t have PS nor SBR so will essentially get something akin to “Skype” quality audio.

      That being said, if they were really nice, they should probably split out another 128kbit/s from the video stream and just change over to 192kbit/s MPEG-1 Joint-Stereo just to make sure everyone can hear it because there are quite a few sets which can deal with H.264 but not AAC-HEv2. This is likely NOT just an encoding issue but an encapsulation issue, as the time the tuners were made/firmware was written, there wasn’t a standard way to shove AAC into TS packets. I believe the encapsulation mode used is called LATM (Low Overhead Audio Transport Multiplex), and some tuners can’t deal with it even though technically speaking, DVB did define its use since 2004. This is why it is confusing as some TVs may advertise MPEG-4 H.264 or AAC-LC/HE/HEv2 compatibility but only because they can play them when in an .mp4 container but then fail miserably when it’s coming over the air.

      The people complaining they are missing out need to remember that this is free to air digital TV. Nothing is a given. Nothing is to be expected. In fact, I can’t say 1/10th of what is aired is worth watching. I know it sucks to miss out, but it’s not worth pulling your hair out or buying a new TV over. Back in the old days, the main concern was to make sure that you could access just their main channel on SD STBs (and I think this concept still persists today) – there’s nothing really that says that any auxiliary channels must be done in a way to be compatible. The march of progress shall continue onwards, like it or not, but needs to be done at a steady and sensible pace. I’d like to remind you all that most of you didn’t cry when RACING.COM and TV4ME were MPEG-4 video and audio …

      Kudos to Channel 7 for being brave enough to try it … now maybe some time for some sense. I mean, 3Mbit/s for SD in H.264 is quite generous … you only give your MPEG-2 stations about 3-4.5Mbit/s and H.264 is supposed to be twice as efficient …

      – Gough

  9. Greg m says:

    Bad move channel 7. 7flix gets the flick here. Not buying a new recorder for one channel that provides little in the way of difference it programs.

  10. Sadly, I’m in the same boat as many others here: perfect picture but deafening silence from 7flix/Racing.com/TV4ME.

    At least Ten HD launched this afternoon (45 minutes ago actually) and we have DD 5.1 with MPEG-4 H.264. Yay! Whirlpool reckons it’s running at around 5.5Mbps too. http://whrl.pl/Rey7t3

    • Well, looks like this is user error. My Beyonwiz FV-L1 PVR supports HE-AAC just fine; turns out my AV Receiver doesn’t. Changing the Beyonwiz stereo audio setting to “Decode” instead of “Passthrough” (but leaving AC3 at “Passthrough”) results in perfect audio on 7Flix/TV4ME/Racing.com. So that’s ace 😀

  11. Ryan says:

    I’ve just noticed that 7flix now has working sound on my older Pioneer LX, which previously could not pick up the audio on 7flix launch (I don’t think it can decode HE-AACv2). Any chance you could do another scan to see what changed? It’s possible they’re now using mainstream low complexity AAC due to the complaints they received.

  12. Gloria Campbell says:

    I think channel 7 should have worked out all the kinks before releasing the new channels. I was looking forward to seeing something other than sport and reality shows but now am stuck with them as I can’t afford another TV. Way to go Channel 7. Gloria

  13. Peter Tapp says:

    have older TV with hd set top box get go sound and still pcture of loudspeaker and don’t know why

    • lui_gough says:

      If pressing the mute button doesn’t resolve this, it normally indicates the set top box does not support AAC-HEv2 audio, as this was not part of the DVB-T standard at its inception and was not a requirement of DVB-T certification. As a result, it sees the channel as having no audio channels, hence the icon indicating that it couldn’t get any audio on the service.

      This is mainly because of Channel 7’s bitrate budget and their engineering team’s choice of using a more recent form of encoding which is not universally supported to allow for better quality and more services on their limited amount of bitrate.

      – Gough

  14. lewis says:

    Well it doesn’t surprise me l cant receive 7flix. Channel 7 would definitely increase their ratings simply by switching all their 7flix programs with the main channel. until they do l will continue to ignore the 7 network altogether. Poor souls cant even choose a decent midday movie to screen. Being politically bias, surely the powers to be can get help from the government with the election looming.

  15. rita says:

    i have a brand new samsung smart tv UA60JS7200W purchased in january and despite calling samsung several times, retuning stations and ensuring i have the correct software upgrade, still no joy. can anyone assist as i really miss my morning tv4me… thank you…

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