Transcoding surround sound for FreeviewHD

41 Responses to “Transcoding surround sound for FreeviewHD”

1. Freeview HD - 5.1 Dolby Digital Surround? - AVForums.com - Page 2 said:

   May 20, 10 at 08:58

   [...] My roundup of boxes has just been published on RegHardware, so I've put the summary list of which kit I've tested can transcode, and which can't, on GoneDigital. I shall aim to update it with more information as I test more kit. It's at Gone Digital | Transcoding surround sound for FreeviewHD [...]

2. 

   Alastair said:

   May 20, 10 at 10:48

   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?

3. 

   Nigel said:

   May 20, 10 at 11:23

   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.

4. 

   tony lord said:

   May 21, 10 at 10:20

   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 ?

5. 

   Nigel said:

   May 22, 10 at 12:52

   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.

6. 

   Paul said:

   May 24, 10 at 11:56

   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.

7. 

   Interceptor121 said:

   May 24, 10 at 22:57

   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

8. 

   Nigel said:

   May 25, 10 at 09:08

   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.

9. 

   Interceptor121 said:

   May 25, 10 at 19:32

   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

10. 

    Nigel said:

    May 25, 10 at 19:38

    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.

11. 

    Interceptor121 said:

    May 25, 10 at 23:34

    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?

12. 

    Nigel said:

    May 25, 10 at 23:38

    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.

13. 

    Interceptor121 said:

    May 25, 10 at 23:40

    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

14. 

    Interceptor121 said:

    May 25, 10 at 23:51

    I meant of course home theatre with multichannel AAC

15. 

    Nigel said:

    May 26, 10 at 09:03

    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.

16. 

    Kate said:

    May 26, 10 at 09:40

    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?

17. 

    Nigel said:

    May 26, 10 at 10:40

    No. You need an STB that can do the conversion internally.

18. 

    Dick Emery said:

    May 27, 10 at 05:28

    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.

19. 

    Interceptor121 said:

    May 29, 10 at 16:46

    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

20. 

    Nigel said:

    May 29, 10 at 18:11

    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.

21. 

    wkdboy said:

    Jun 02, 10 at 00:23

    i have got the philips dtr5520 into my yamaha dsp 763 an its shows DD 5.1 on the front but the sound only comes out the front two.

22. 

    Nigel said:

    Jun 02, 10 at 09:19

    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.

23. 

    petrev said:

    Jun 02, 10 at 12:54

    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

24. 

    Interceptor121 said:

    Jun 02, 10 at 18:04

    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

25. 

    figrin_dan said:

    Jun 03, 10 at 12:16

    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

26. 

    petrev said:

    Jun 05, 10 at 12:05

    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

27. 

    figrin_dan said:

    Jun 08, 10 at 11:58

    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

28. 

    Nigel said:

    Jun 08, 10 at 17:16

    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.

29. 

    TomT said:

    Jun 10, 10 at 15:28

    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?

30. 

    Nigel said:

    Jun 10, 10 at 15:39

    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.

31. 

    TomT said:

    Jun 10, 10 at 16:37

    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.

32. 

    Nigel said:

    Jun 10, 10 at 18:14

    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.

33. 

    XMB said:

    Jun 12, 10 at 10:33

    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!

34. 

    Nigel said:

    Jun 14, 10 at 12:39

    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.

35. 

    Loz said:

    Jul 31, 10 at 16:56

    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.

36. 

    Dan said:

    Aug 19, 10 at 09:30

    My Sony KDL-37EX403 transcodes to 5.1 DD on BBC HD!!

37. 

    Kai said:

    Aug 19, 10 at 21:00

    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.

38. 

    Richard said:

    Sep 01, 10 at 07:57

    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. “

39. 

    Nigel said:

    Sep 01, 10 at 10:09

    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.

40. 

    alufo said:

    Sep 01, 10 at 14:19

    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.

41. 

    Nigel said:

    Sep 01, 10 at 14:27

    Sorry; yes, that should be DD 2.0 rather than 5.1. I’ll update the list.

Leave a Reply