Dual Freeview tuner that supports audio description?

Discussion in 'Home Entertainment Computers' started by ItsBen, Jul 4, 2015.

  1. ItsBen

    ItsBen
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    Hi all,

    I'm in the early stages of planning my HTPC build but I'm a little stuck on which tuner to get. I'm totally blind & I enjoy audio description, but I'm really strugglling to find a dual Freeview tuner that is definitely able to receive it.
    Additionally, I'm having a hard time trying to work out if either WMC or Kodi will actually let me toggle the audio description on or off, even if my tuner supports it.

    I know this is a massive ask, but I'm really looking for someone who has a bit more experience with tuners than I do who can say conclusively that tuner X can receive AD & software Y will let me toggle AD based on their current setup or a setup that they've delt with in the past. If it were just a software issue then I wouldn't mind taking the time to test things myself, but I really don't want to buy multiple tuners only to find that none of them do what I want them to do. NB: I'd prefer PCIE but would settle for USB if it were my only option.

    Does anyone have any ideas? Proceding with the build is more or less pointless until I've sourced a tuner so I'd really like to find an answer. NB: I am aware of the talking Freeview boxes - I currently own a Tvonics, but they've gone out of business & if you're blind & want DVR / VOD functionality in one device a computer is the only way.

    Many thanks,
    Ben.
     
  2. Rambles

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    Hi, I just did a quick test of this for you on my set up - Argus TV with MediaPortal on Freeview. Whilst playing live or recorded TV it is possible to select a menu to list all of the available audio tracks, BUT, it would only let me select one at a time, the first one was the usual audio, the second selectable one was the audio description, but this only had the narration and none of the actual dialogue, so I guess it's no good.
     
  3. ItsBen

    ItsBen
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    Thanks for trying anyway. Mediaportal's completely inaccessible so I wouldn't have been able to use it even if it did work.
     
  4. robbo100

    robbo100
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    Hi @ItsBen

    Notwithstanding the fact you don't want MediaPortal, the NAR stream will work with the AD and background audio on MediaPortal, @lisag, maybe you didn't have your AV receiver set to correctly map the audio channels - did you try it in normal Stereo?

    With MediaPortal, if deselect the option "prefer audio type over language" (TV - MediaPortal Wiki this will generally mean that AD audio is set to come on as a preference (in the UK).

    In terms of hardware, the AD audio is carried as part of the DVB-T or DVB-S Transport Stream, therefore, it should make no difference what hardware you have. It purely comes down to whether your software supports it.

    I am willing to bet that WMC doesn't (but I may be wrong), and I am fairly sure that Kodi can select audio streams, but it depends upon the TV server you are using. If you use the MediaPortal TV Server, then it will.

    When you say you don't want to use MediaPortal, because it is not accessible, what element of it is the problem? TV Service or the Client side?

    All the best.

    Robbo100
     
  5. ItsBen

    ItsBen
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    Thanks - this is all really useful information!
    In terms of MP's accessibility I meant that the client isn't accessible - E.G. a few screen readers under Windows just didn't read anything once it was opened, but I heard beeps when I pressed the arrow keys so I assume that visually it was ok.
    I'll investigate using MP as the backend and Kodi as the frontend. It would be good if I could configure the TV server myself, but in practice I may just get someone too remote in and do it for me & backup the modified configuration in case I ever need to restore. Do you happen to know if I would be able to toggle AD using Kodi with the MP TV server? I know that's probably a question best asked on the Kodi forum so no worries if not.

    Bit of a rant here but I'm a bit annoyed at how hard this is turning out to be. There are a few options from Samsung in terms of accessible TV's but you don't get access to the entire feature set of the TV so if you want VOD functionality you end up having to buy another device anyway. Usually people go for an Apple TV, but the selection of services you can access from it in the UK is pretty poor IMO so realistically you need an iDevice to Airplay content to it. You then have the problem of inaccessible apps - 4OD / 4All is a good example.

    Many thanks once again to everyone who has contributed so far.
     
  6. plum23

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    Just checked with Kodi and tvheadend backend - same issues as in post #2 - you can select the AD track, but then there's none of the usual audio dialogue etc that is on the main track.

    There's a feature request to mix the two as you would need, but no progress as yet.
     
  7. robbo100

    robbo100
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    Hmmmm

    It seems like @lisag didn't have a mixing issue then! That is disappointing to say the least.

    In terms of a bug fix, this is a client side issue not a server side (IMHO).

    I will ask on the MediaPortal forums and report back.
     
  8. robbo100

    robbo100
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  9. plum23

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    From a bit of reading around it seems that Freesat has 2 tracks, one of which is the AD mixed with the dialogue, so would work with Kodi; whereas Freeview just has separate tracks. Don't have a sat adapter to check, but might be an option?
     
  10. robbo100

    robbo100
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    Ahhh. That explains it!
     
  11. robbo100

    robbo100
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  12. Trollslayer

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    The complication with AD is that it has to be mixed with the main audio (this is why broadcasters switched to AAC).
     
  13. Rodders53

    Rodders53
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    freesat has separate pre-mixed tracks for normal audio and AD audio... mainly to accommodate $ky receiver limitations at the time, if I recall correctly... so freesat receivers have to use the same system (despite the BBC wanting a better way to do it where the user controls the mix). The AD mix is a poorer quality audio than the main (i.e. a lower bitrate is used for AD).

    The Freeview(TM) specification was always for the two audios to be mixed in the receiver with (ideally at least) the ability for the user to adjust the levels of the AD and main audio to suit their preferences. {The broadcasters also have some control on main audio duck levels and timings via the transport stream metadata}. As a side-effect it also saves slightly on overall audio bitrate.

    HTPC DTT tuners seldom (I hesitate to say never) meet the Freeview specification and DTG testing regime, so do not support this UK-specific feature. Of course anything is possible in software, if someone with the necessary skill and knowledge is willing to spend the time in writing it.
     
  14. Trollslayer

    Trollslayer
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    I believe that was for AC-3 audio, AAC allows mixing, not sure of the technical details.
    As to HTPC DVB-T2 tuners not meeting test regimes, that can affect sensitivity and noise immunity but won't affect the transport stream as long as it is not corrupted and such corruption would not be related to the content. Certainly the DTG maximum signal level (as far as I can remember) seemed to be far too high to me.
     
  15. Rodders53

    Rodders53
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    BBC had R&D/D&ED audio description units that did it all in analogue, back in the day to develop the mechanism. IIRC the AD track was broadcast as an extra low-quality mono signal within Nicam-728 (intended for 'broadcaster use' such as cue to outside broadcasts)... but it was a fairly long time ago, and memory is a bit hazy... I'd need to search for the White Papers to be sure.

    Mixing is down to having sufficient audio decoders present plus a little extra electronics... maybe a licensing cost issue for some?

    AD is available on Standard Definition Freeview and freesat transmissions and has been specced so from day one of UK DTT - so nothing whatsoever to do with AAC (as used in DVB-T2 HD here in the UK).
     
  16. Trollslayer

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    I was just thinking about the internals of the chips (again).
     

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