Transcoding surround sound for FreeviewHD

As you can read here, surround sound on Freeview HD isn’t quite as straightforward as on some other digital television services. Unless you have incredibly up to date surround equipment, then you really need to make sure that the Freeview HD receiver you buy is able to transcode from the HE-AAC format to Dolby Digital, so that your existing equipment will be able to understand it, and produce proper 5.1 surround, rather than just stereo.

(For a basic introduction to surround sound, click here).

As part of my testing of Freeview HD boxes, I’ve checked them to see whether or not they do transcode; testing was conducted by connecting the S/PDIF output of the box to an input of my Yamaha DSP-E800 surround decoder. If the display on the decoder indicates that it’s receiving Dolby Digital, then the box is transcoding.

When it comes to televisions, I think you can fairly safely  assume that the audio functionality on different screen sizes in a particular range is going to be the same; it would be most unusual if, for example, a 32 inch set transcoded, but a 42 inch model in the same range didn’t. Note that you should compare model ranges carefully – for example, the Sony KDL-46EX403 and KDL-32EX403 are both the same range, but the Samsung LE40C650 and LE40B650 are not. And, if in doubt, specify to the retailer that this is a required feature when you purchase, so that you are within your rights to reject a product if it doesn’t transcode. I cannot accept responsibility for errors or omissions.

I shall try to keep this page up to date, based on my own tests and reports from other people. Originally published on 20th May 2010. Updated 17th April 2011.

Equipment confirmed to transcode

  • Bush DVB680; transcoding via optical digital output (note 1)
  • DigitalStream DHR8203U, DHR8205U, DHR8206U (twin tuner recorders); transcoding via optical digital output (note 2)
  • Humax HDR Fox-T2 (twin tuner recorder); transcoding via optical digital output and HDMI
  • LG 42LE5900 (Freeview HD TV); transcoding via optical digital output
  • Philips DTR5520; transcoding via co-axial digital output, NB only two channels.
  • Samsung LE40C650 (Freeview HD TV); transcoding via optical digital output
  • Sharp LC46LE821 (Freeview HD TV); transcoding via optical digital output
  • Sony KDL-46EX403 (Freeview HD TV); transcoding via optical digital output
  • Toshiba 40RV653 (Freeview HD TV); transcoding via optical digital output
  • TVonics DTR-Z500HD (twin tuner recorder); transcoding with firmware V1.2.A1615.D300.F100

Reported as transcoding by other people:

  • Humax HD-Fox T2 (with firmware update)
  • Samsung PS63C7000 (Freeview HD TV)
  • Sony KDL-46EX503 (Freeview HD TV)
  • Sony KDL-40HX703 (Freeview HD TV)

Equipment confirmed not to transcode at present

  • Goodmans GDB300HD
  • i-Can EasyHD 2851T (to be added in an update, according to ADB)
  • Icecrypt T2200
  • Icecrypt T2400 (twin tuner PVR)
  • Panasonic DMR-XW380 (twin tuner DVD recorder)
  • Panasonic 2010 Freeview HD TV sets (all models)
  • SagemCom RTI-90-320 (twin tuner recorder)
  • Sharp TU-T2

Notes

1. The Bush model is actually made by Vestel and is their T8300. Generally, the features do not differ between the differently branded versions of this unit, and so it is a fairly safe assumption that all the other T8300 products also produce a Dolby Digital output. Here are the other names by which the box is known.

2. Transcoding to Dolby Digital was added to the Digital Stream models in a firmware update. All three models are identical save for their disk size (320Gb, 500GB, 1TB respectively). You need at least version 3.51r5849. Download updates here.

58 thoughts on “Transcoding surround sound for FreeviewHD

  1. Just wondering if any of the new TVs which have built in FreeviewHD decoders have the ability to output surround sound, or is it necessary to buy a separate FreeviewHD box?

  2. The Panasonic I’m testing doesn’t output Dolby Digital on the optical connection. I have some other FreeviewHD sets that I’m playing with over the next few days, and I shall update the list here when I know more.

    Some sets may output multi-channel audio over HDMI, but unless a friendly PR arranges a loan of a suitable AV receiver, I won’t be able to test that at the moment.

  3. Nigel

    you’ve tested the Philips DTR5520 as confirmed. Will you be testing the Philips recorder HDT8520 soon ? Do you think it’s risky to assume the HDT8520 will transcode just because the DTR5520 does ?

  4. I’d say there’s a pretty high likelihood, but I wouldn’t want anyone to rush out and spend money on that just because I hope so.

    I’ll be trying to get as much of this kit in as I can, but it’s not always easy – seems to be in very short supply right now.

  5. I’ve had it confirmed by 3view tech support that the upcoming 3View box (www.3view.com) ‘is a licensed Dolby Digital Plus box and we do support transcoding of AAC to DD / DD Plus’. The box hasn’t shipped so I can’t verify.

  6. As of today there are no home theather that can decode multichannel AAC so the only way is to convert into 6 discrete PCM channels
    However optical or coaxial do not support multichannel PCM therefore whoever is reporting those receivers to work through optical is having a dream unless they decode and reencode real time to AC3 (unlikely)
    The only option is to pass the multichannel PCM once decoded through HDMI so if you have optical you can forget about DD

  7. Why do you think people are dreaming, and that real time AC3 encoding is unlikely?

    If you read the rest of this blog (or do some online reasearch), you’ll find that there are in fact chipsets in production, and designs, specifically for this task, not least because it’s a mandatory requirement in various countries.

    For example, read http://gonedigital.net/2010/05/20/updating-freeviewhd-boxes-for-surround-sound/ and follow the link for information about the Dolby MS10 design, already being used in chipsets from NXP, and able to do just what you consider to be unlikely. Broadcom also have chipsets capable of real time encoding, though I’m not sure they use the Dolby design.

    So, no, neither I nor any of the other people reporting AC3 output from optical are dreaming. It does work, and manufacturers are working to enable it on other bits of kit too, where the chipsets they use support it.

  8. I was referring to TV with integrated receiver such as Panasonic and Sony those only pass through signal do not rencode so your only chance is to buy a receiver that does that job which will cost you as much as a sky HD box which will have genuine AC3

  9. There’s absolutely no reason why a TV can’t use some of the chipsets from firms like NXP that do feature transcoding.

    And, in fact, of the Freeview HD sets that I’ve been looking at, the Sharp Quattron does indeed output AC3 via its optical port when tuned to BBC HD. I verified that for myself over the weekend.

    Remember that many TVs, aside from the DVB-T2 tuners, will be models that are designed for the whole of Europe; in fact, the pre-production sample of the Sharp that one of my colleagues tested before I got the UK one was identical, other than in respect of the tuners.

    And for many countries in Europe, transcoding is mandatory, so the necessary chipsets – which are much the same as those for a set top box, after all – will be present in the TVs too.

  10. I do not know about this Sharp tv I can only see it says it can decode AAC multichannel which is already a result but then it says AC3 output none?

  11. Well, take it from me – it transcodes to AC3. I’ve had it in my living room, doing just that.

    AC3 output, via optical, from a channel broadcast AAC multi-channel audio.

  12. Probably they planned to have the chipset capability that other did not include.
    I still think that AAC to multichannel PCM over HDMI is the best solution as the there is no decoding and encoding
    Even better would be to have receives that can decode multichannel AAC so that receivers only have to pass through

  13. That will come, in time; when it does, it will most likely appear on kit under the ‘Dolby Pulse’ brand name, which is their name for HE-AAC with some added Dolby information.

  14. If you have an STB that has Dolby pulse as an output is there any way available to convert that into a Dolby Digital output?

  15. I can confirm that the Panasonic TX-P??G20 range does not transcode to Dolby Digital over the optical SPDIF output. Just plain old PCM. My amp is older and does not have HDMI so no idea if it sends to the HDMI audio return path as multi-channel sound.

    I hope there will be an OTA upgrade to enable transocding. I will pester Panasonic about it.

  16. The G20 do not even decode HE-AAC on audio files
    If you try to play an .AAC file with PS or SBR (HE-AAC v1 or v2) it can’t play it
    So if BBD had to start using HE-AAC instead of AAC as current the Tv will go silent

    1. Since you’ve seen fit to post this here, as well as on AV Forums, I’ll post here the reply that explains why you are wrong and why I think you’re just posting ill-informed scaremongering:

      Have you actually verified what you’re saying, in the only reasonable way – with a DVB-T2 stream generator, and a properly modulated stream that has HE-AAC audio?

      Didn’t think so.

      How did you try this test? Be aware that the media playback facilities on many sets bear absolutely no relation to the capabilities of the rest of the system, and may even depend on the source medium.

      For example, via DLNA, a Sony EX703 will play back nothing much beyond an MPEG2 stream. It won’t even play back H.264 video encoded in an MPEG2 transport stream, which is what is broadcast on Freeview HD, and which it can certainly understand via its tuners. Give it the same thing from a DLNA-serving Panasonic Freeview HD recorder, and it won’t play it. But it will play many more formats from USB memory.

      A Pansonic TV will play that via DLNA, but won’t play back any audio other than mp3 via DLNA or from solid state media. Even within a particular container format, compatibility varies between software versions. Last year’s DLNA Panasonic sets didn’t play any music, for example, and I have some AVI files that makes them reboot – but the same files play ok on this year’s, like the D28 I have here. Conversely, the D28 stalls when playing a file that worked fine on the V10.

      And if I were to give the V10 an H.264 video stream encapsulated in a transport stream, it wouldn’t play it. And I think we can all agree it would be foolish to claim on the basis of that that it doesn’t understand H.264 video – because it can tune into Freesat HD.

      In short, you almost certainly do not have evidence that proves what you say it does. And in the absence of that, to start telling people their Freeview HD sets will suddenly go mute at some date in the future is irresponsible, in my view.

    1. What were you watching? Last night, for example, there were only two programmes with 5.1 audio on BBC HD in the evening, plus one of the children’s programmes. Of the two peak programmes, one was ‘A little Later’ and the other was ‘Amazon’

      The rest was just in stereo, so you wouldn’t have heard anything from the rear speakers. The majority of programmes don’t have surround at the moment.

  17. Hi

    You can add Sony KDL-40HX703 (Freeview HD TV) to the 5.1 GOOD List.

    My Test Philips HDT 8520 does DD2.0 but not DD5.1 ? ? ?

    Keep up the pressure on Manufacturers and Broadcasters if you can
    Pete

  18. Maybe you did not read my other post
    The tv does decode HE-AAC once I found the right container and it does do H.264 so in theory it should manage through a firmware update
    There is always a way to test which codecs a Tv can handle and the firmware usually takes care of the containers
    i rectified my position on the HE-AAC based on the same conclusions
    I also have to say from previous experience with HE-AAC that for some reason it is a hard format to handle for multichannel and most of the implementations downmix
    XBMC has now an AC3 transcoder which would be the first time I have seen that working successfully however a linux or windows machine offers much more flexibility than a Tv firmware so maybe the multichannel won’t be posslble

  19. wkdboy and peterv. That sounds (to me) like either the stb is transcoding to DD but not properly to 5.1 or the programme was flagged incorrectly. If it was supposed to be only stereo (and not flagged as 5.1) The Yamaha amp will not say 5.1 and will default to DPL

  20. Hi

    I just know that while 5.1 is being transmitted (eg. BBC-HD Test) the digital output from the Philips/Pace is DD2.0 – detected by my Nakamichi AV8.

    Same program output from my KDL-40HX703 is detected as DD5.1

    Same program output by DigitalStream is PCM Stereo.

    Cheers

  21. So the possible outputs of a freeviewHD box, tuned to an AAC5.1 channel, could be any of the following:

    HDMI:
    PCM 2.0
    PCM 5.1

    SPDIF:
    PCM 2.0
    DD 2.0
    DD 2.0 (Flagged as 5.1)
    DD 5.1
    (and possibly)
    AAC 2.0
    AAC 5.1
    dts 2.0
    dts 2.0 (Flagged as 5.1)
    dts 5.1

    1. Yes, that’s pretty much it. So, things are even more complicated than they first appeared when I started exploring all this.

      There are clearly some bits of kit that transcode everything, and some that seem to transcode only two channels. But given the time scales I’ve had to test this in, and the equipment available to me, it has not been easy to verify all the possibilities. Incorrect flagging of some broadcasts also makes matters more complicated.

      Really, the only people who can do this reliably are the DTG testing labs, I think.

  22. I have to agree with Interceptor121. I can’t quite see the point of requiring extra transcoding support in the STB, just in order to keep what I would regard these days as ‘legacy’ AV receivers happy.
    I think all AV amps now are HDMI1.3 are therefore I would expect to happily support multichannel PCM. So we just decode HE-AAC to LPCM in the STB and let the AV amp do the rest.
    The only reason that trasncoding would be necessary in my opinion is to support an older AV amp over SPDIF (SPDIF only has the bandwidth for compressed (Dolby/DTS) multichannel, not LPCM mulitchannel). But if you’re amp is that old, you should be replacing it anyway.
    For the user without an AV amp, this whole discussion is redudnant – why would you be bothered about multichannel audio when you only have the crappy capabilities afforded you by the TV speakers?
    Or have I missed something?

    1. I’d say that what you’ve missed is that while “if your amp is that old, you should be replacing it” is just fine for people with money to throw around, the vast majority of people don’t have all that spare cash.

      There are AV amps still on sale that don’t support multi-channel PCM (look at Richer Sounds), and there are lots of people who do have what, as far as they are concerned, are perfectly acceptable surround sound systems, which will almost all work with S/PDIF inputs.

      Mandatory transcoding (which is coming, but not until next year) means that those people don’t have go out and buy another bit of kit, just to get a feature that they will have expected, from the wording of Freeview’s site, they would have got in the first place.

      Of course, there will be plenty who don’t care about surround at all. But it’s not that hard to cater for the installed base of surround systems, and there should at least have been more information making it clear that that might not be the case, rather than the claim that if you have a 5.1 system, you just need to hook up your Freeview HD kit.

  23. OK from that point of view, fair enough. Yes I would say that they have ‘mis-sold’ their claims in this respect, and I would suggest that the BBC have backed themselves into a corner here.

    This was always going to be an issue with SPDIF connected equipment – there is not the bitrate to support non-compressed multichannel; but then HDMI came along which opened up the options again. Why AV manufacturers haven’t adopted AAC more widely, I’m not sure. Compared to the Dolby-TrueHD and DTS-MA standards that are widely supported now, the marginal costs of AAC licensing are small (but these things are built to a price of course, so it all counts).
    I’d be interested how other countries are tackling this one; they will have all the same AV equipment as the UK but they of course have different broadcasters.
    Bit of a mess really. I think this mandatory transcoding is going to be a pain for chipset manufacturers. They’re used to having a tidy audio DSP that’s built for one thing – decoding. To re-engineer the pipe in order to re-encode is not just going to cost design time & chip area, but the extra encoding license as well. Of course it will just come back on the consumer in the end though.

    1. Well, in most of Europe, both HE-AAC and Dolby Digital Plus are supported standards for their HD broadcasts, so we’re not alone in this, and in many countries, it appears that transcoding is mandatory, too.
      In fact, it shouldn’t be too much of a problem, as there are specific designs that are intended to do this, like Dolby’s MS10, which is already used in TV chips from NXP – you can find a link to the Dolby paper in my post on updating boxes. One aspect of that design is that it’s intended to simplify the licensing issue as well.

  24. The real question is why was transcoding not mandatory from the outset? As soon as the UK decided to use the HE-AAC format it was obvious transcoding would be needed for compatibility with the bulk of the audio equipment used.

    You can add the Sagemcom RTI90 products to the list of devices that do not support transcoding and in fact do not even support 5.1 over the HDMI connection! (See the user manual specifications on page 45.) The marketing and front panel graphics show Dolby Digital logos but this is meaningless in the UK!

    We need Obama to kick someone’s ass!

    1. The reasoning that I’ve been given is largely to do with the long lead times on products, especially from the bigger companies, who are designing equipment for a european-wide market, rather than specifically for the UK. UK models are often pretty similar, with just firmware differences, though at the moment, we also have different tuner modules, but that’s not generally a major issue – even DVB-T2 tuners are still outputting an MPEG standard transport stream, when all’s said and done.
      AAC is used elsewhere in Europe, but there aren’t of course many HD services yet, and it’s the use for the surround that’s the quirk of the UK. I’m told by fairly reliable sources at some of the manufacturers that at the time the decision was taken to use AAC for everything, they’d already picked the silicon that would be used for the 2010 model year sets, and it wasn’t stuff that could do the transcoding. When you’re creating sets by the millions, for the whole European market, I guess you need to be sure of your supply lines a lot further in advance than the smaller companies.
      I’d guess that faced with the news that the big name manufacturers wouldn’t be able to include this in their sets, the people (which includes the manufacturers, remember) drawing up the DTG specs would decide that it’s far better for them to have a launch where these features are not mandatory, than a launch where the expected big names didn’t have products to sell.
      So, from a pragmatic point of view, you can see how we ended up there; mandatory transcoding from the start would have been the ideal solution. Realistically, to get the big names on board which would help with the marketing push, that probably wasn’t going to happen. But once that decision was made, there really should have been a much clearer effort to communicate to the customers exactly what the situation was with surround sound, and that’s the second (and perhaps least forgiveable) big mistake.

  25. Thanks for this useful and informative post, this seems to be the only source of this information as it’s certainly obvious from the specs on these tvs whether they do or not.

    I’m just hoping to see some of the smaller telly crop up on here that might be inside my budget.

  26. I’m considering a Samsung UE40C7000 which has a 4 HDMIs and a single HDMI ARC (Audio Return Channel) socket and Samsung claim it is both Dolby Digital Plus and Pulse.

    Now I don’t have a Surround Sound receiver, but can this TV even output a surround sound signal on HD Freeview? Is it via the HDMI socket or via the optical digital sound socket?

    If it does then do I have to get a surround sound receiver with a HDMI 1.3 or 1.4 with ARC?

    I’m looking to upgrade to a new TV, I decided to get one with Freeview HD built in and never even thought you wouldn’t get 5.1 surround out of it if you bought a surround sound receiver/amplifer.

  27. In case it helps anyone, I received the following reply from Sony UK regarding TV model KDL-40EX603

    ” I can confirm that the Sony KDL-40EX603 is not capable of transcoding audio signals. It can only output whatever signal it has received. “

    1. I have to say, I would be quite surprised if that’s the case, given that the entry level 403 range transcodes, as do the 503 and 703 models. So it would be unusual if all of those did, but not the 603.
      However, one thing I have learned in my researches into the surround sound issue is that even people who ought to know the answers very often don’t, and people on support lines sometimes aren’t as well informed as you’d imagine.

  28. you state that the philips dtr 5520 transcodes to d.d. 5.1
    yet pace admitted to What Hi-Fi magazine on 22/6/10 that it doesn’t?
    which philips own current documtation admits.

  29. Anyone know if broadcast 5.1 surround sound can be got out of the Panasonic 2010 Freeview HD TV sets using the HDMI connection into an AV amplifier with HDMI input?

  30. We can add the Sony KDL-40EX713 to the good list.
    The S/PDIF link outputs 5.1 Dolby D transcoded from Freeview HD AAC received by the internal tuner.

    The S/PDIF link also outputs Dolby D 5.1 as-is when received from an external source via HDMI.

    (But apparently not DTS 5.1 received from an external source via HDMI).

    Hope this helps

  31. Got this from LG:

    Thank you for your email.
    All of our televisions output digital audio via the optical port. So an optical audio cable is required. The television will not process the audio, it is down to your amplifier as the television will only convert a 5.1 signal into a Stereo signal using it’s built in speakers.

    Not sure they even understood the question!

    Im looking for a 37″ TV Freeview HD with SPDIF output,

  32. Bought a Sony 37″
    Output is 5.1DD as required, am pleased with it
    One small peculiarity:
    The user has a choice of setting either optical out or TV speakers, not both.
    This causes consternation when the TV is switched on and no sound can be heard.

    1. Yes; it’s annoying isn’t it, especially if you want to use one sometimes, and another at other times, for example just the TV speakers when you come home late from the pub, and don’t want to wake anyone up.

  33. Please can anyone confirm what the situation is with Luxor 690 HD box producing surround sound? My Sony home theatre system is only producing stereo when linked up to the box via the optical. I’ve had a look at the product info on the label and it mentions the T8300 which I thought supported Dolby Digital. I’ve had a look at the configuration menu and the only options are PCM and Bitstream.

  34. Continuing from my last post. I’ve just read the BBC article from last year which was very helpful. I’m guessing the programs I’ve been watching haven’t been in 5.1. I’ve only just started using the box again after about 6 months. I haven’t a clue on the amount of 5.1 broadcasting at the mo.

    1. If you have access to DigiGuide, that will sometimes tell you which programmes are in 5.1. That said, it’s not showing anything as 5.1 this evening on BBC 1HD or BBC HD – though I had a feeling Silent Witness was. There isn’t a massive amount, though films tend to be, and some of the imported drama on Channel 4.

  35. Thanks for that. I’ve noticed alot of the shows on that guide say stereo. Does that mean 5.1 or will it actually say surround or 5.1?

    1. It usually says ‘Dolby Digital 5.1’ for shows with a surround soundtrack – though looking through the BBC HD listings, I didn’t spot any until Saturday, when ‘Tinga Tinga Tales’ at 14.50, 15.30 and The Tudors at 22.00 followed by Nurse Jackie at 23.00 are supposed to be in 5.1

  36. Hello, just bought the Technika STBHDH2010 (Harvard?) box from tescos as it was on sale, just want to ask does it do transcoding for 5.1 surround? it has DolbyDigitalPlus on the front of the box, connected up to my Sony surround system which does DD/DTS/LPCM, I set technika box’s Audio Output to Dolby but got no sound? does that mean the box is not doing transcoding, or just my system don’t support DD+?

    will there be any firmware updates to get transcoding working for this range of boxes or is it a hardware limitation?

  37. I tried to get 5.1 from my Panasonic TX-P42G20B from SPDIF and HDMI2 audio uplink, to a Sony AV amp. Nothing other than stereo. I noticed that broadcasts with HE-AAC soundtracks have very much reduced volume on the TV.
    I also tried a Panasonic BWT700 twin-Freeview HD recorder. When using the tuner to watch live TV with HE-AAC soundtracks then all you get is stereo. Also if using it as a DLNA server to the G20 TV all you get is stereo. However, if you record a programme on the BWT700 with HE-AAC soundtrack, it plays back in Dolby 5.1. I am not sure when it does the transcoding but it does not seem to do it on the fly.

  38. Not 100% on the ball with this but…

    After getting my youview box last week I’ve wired it up to my sony 40ex503 TV via HDMI then passed the audio back to my Onkyo507 SS amp via an optical cable. This combo seems to successfully deal with freeview HD surround sound (e.g. Homeland on C4HD the other night in 5.1 according to the onkyo) and for the other HD channels it is claiming a ProLogicII audio source.

    So far, so good, I’m pretty happy with that.

    However, should the Sony TV also be able to deal with SS audio inputs as well (i.e. when using its own tuner and not the youview box?). In this situation the Onkyo receives PCM audio only. Its not much of a concern as the youview box does SS anyway but its made me curious!

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