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Thread: Dolby 5.1

  1. #31
    adm's Avatar
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    Being a bit more critical in what I'm seeing/hearing

    There seems to be a lip-sync problem between vision and ACC downmix audio over HDMI and SPDIF that appears uncorrectable on the Miraclebox Twin Premium. There is a PCM delay option in the AV menu with a range -1000 to +1000 but this doesn't appear to make any difference to the mismatch (audio ahead of vision).

    What I'm observing is with a TV connected via HDMI and using the TV (non-surround) audio/speakers, and as a second test with SPDIF audio into an AV amplifier.
    Last edited by adm; 04-10-14 at 01:07.

  2. #32
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    Quote Originally Posted by adm View Post
    There seems to be a lip-sync problem between vision and ACC downmix audio over HDMI and SPDIF that appears uncorrectable on the Miraclebox Twin Premium. [...]

    What I'm observing is with a TV connected via HDMI and using the TV (non-surround) audio/speakers, and as a second test with SPDIF audio into an AV amplifier.
    I'm not aware of having seen this.
    There is an AudioSync extension, which might have additional options. (The relevant source files are all named AC3*, but ...).
    MiracleBox Prem Twin HD - 2@DVB-T2 + Xtrend et8000 - 5(incl. 2 different USBs)@DVB-T2[terrestrial - UK Freeview HD, Sandy Heath] - LAN/USB-stick/HDD

  3. #33
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    Quote Originally Posted by birdman View Post
    I'm not aware of having seen this.
    There is an AudioSync extension, which might have additional options. (The relevant source files are all named AC3*, but ...).
    I suspect that the functions of some of the plugins have already been incorporated into the existing VIX image. There is already an inbuilt AC3 and PDM audio delay option but these don't seem to apply to to the digital audio output when viewing UK terrestrial TV. As I can only get downmix 2 channel with my (external) equipment I'm currently using the RCA outputs for audio which appear to have better (but not perfectly synchronised) lip-sync, with my set-up.

    I should point out that surround sound isn't new to me. I'm on my second AV amplifier and that was purchased 6 years ago - and before that NICAM stereo on UK broadcasts. Other (4 off) equipment does work as expected with my set-up using SPDIF connections.

    I'm beginning to think that with the existing hardware/software (VIX Apollo image 41) the Miraclebox Premium Twin is unsuited to UK terrestrial TV. It does a lot of things very well but is let down by it's audio capability. Perhaps I'm not surprised as its pedigree seems to be from the satellite background.

    As I've said before I can adapt the box for satellite usage and this may be the way forward for me. I will try with plugins etc. for a while because watching/recording TV is not a priority for me and I must get on finishing my bathroom and refurbishing the central heating before the weather gets too cold
    Last edited by adm; 04-10-14 at 08:42.

  4. #34
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    @adm - please see my post (#30) regarding the inability of MB Twin to transcode AAC to DD, whereas Quad Plus will do so. The MB also does not support HD PiP. Its chipset does not seem to be capable of supporting that. Big price difference between the MB and the Quad Plus, so it's understandable that it is not so capable.
    GB Quad Plus, Mut@nt HD51, AX HD61, 80cm dish and Supreme Dark motor. Sony STR-DN 1060, Sony UHP-H1 Bluray, Odroid N2+ (CoreElec), Monitor Audio Bronze 5.1 speakers

  5. #35
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    Quote Originally Posted by fat-tony View Post
    @adm - please see my post (#30) regarding the inability of MB Twin to transcode AAC to DD, whereas Quad Plus will do so. The MB also does not support HD PiP. Its chipset does not seem to be capable of supporting that. Big price difference between the MB and the Quad Plus, so it's understandable that it is not so capable.
    But is the lack of transcoding from AAC5.1 to, say, AC3 impossible due to limitations of the hardware/software in the box or just because its a low priority or no-one thought it important?

    Price difference may not be a indication of potential performance. More modern chip-sets often have more functionality for a cheaper price, especially if they share some commonality with TV sets that cater for the broadcast standards world wide.

    If its a software issue do any of the other possible images (OpenATV, Egami, OpenMB) do something different?

  6. #36
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    I would assume that if the drivers in the MB Twin exposed a method to do AAC to DD transcode, then it would be included in the image menu as it is in the Quad Plus. The facility is there for other boxes so no additional development needed I would have thought. Someone with in-depth understanding of the underlying image software may comment perhaps?

    You could always try another image to see if AAC to DD transcode is offered. It's just a flash job. You could make a backup of your ViX image first (ViX option in System menu) so that you can easily revert. I had tried other images for the PiP restriction (SD only in PiP) as I had thought that it should support HD in the picture window according to how I had read the specs in the manual, but no image supported HD PiP.
    GB Quad Plus, Mut@nt HD51, AX HD61, 80cm dish and Supreme Dark motor. Sony STR-DN 1060, Sony UHP-H1 Bluray, Odroid N2+ (CoreElec), Monitor Audio Bronze 5.1 speakers

  7. #37
    darucla23
    Quote Originally Posted by fat-tony View Post
    @adm - I've done some more experimenting with settings. I have a Quad Plus as well as the MB Twin. On the Quad Plus I still can't get uncompressed multichannel INPUT to play properly over HDMI. I get two channels of output being played back as 48kHz PCM streams. I guess more work is needed with the drivers etc. But this is sort of specific to my particular situation where I have multichannel FLAC sound files, so maybe ignore this for the moment.

    ...

    Also, on the Quad Plus, but not on the MB Twin, you get the menu option to transcode AAC bitstream to Dolby, so you could use this to pass a transcoded DD 5.1 bitstream over S/PDIF, presumably. So, in your case you could keep your existing AV amp, but would need to upgrade from the MB Twin to a Quad Plus or similarly equipped STB. I presume it's a limitation of the chipset or drivers.
    I see that you are in Ireland. Do you get Freeview+HD type broadcasts with AAC5.1? If so, and you have some recordings, have you tested with off-loading one to a NAS and then playing it back on the Quad Plus (I am assuming that this is what you do with the files with flac)?

    I note that you specifically state that you have the option, but not that you have tested the AAC to DD 5.1 function on a broadcast. If it is just the MB Twin that has this not working, I will seriously consider buying something else.

  8. #38
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    Earlier in the thread I said that I had no way of testing AAC as our domestic terrestrial service (Saorview) does not use AAC currently - just MP2, although the specs dictate AAC support for future use. DD 5.1 to PCM transcoding is available on the Quad Plus as is AAC to DD transcoding. You're correct in the assumption that I haven't an AAC source to test AAC to DD transcoding on the Quad Plus.
    The Miracle Box Twin is a lower specced box so I assume that is why it doesn't have the AAC to DD transcode option in the menu. If you specifically need the AAC to DD transcode (or AAC to multichannel PCM decode) option then you may need to do some research with the vendors or manufacturers. In the same way that a DVB-T tuner is no use in GB for terrestrial HD reception (you need DVB-T2), you also need to be able to either transcode AAC 5.1 to PCM 5.1 or DD 5.1 depending on the capability of your AV amp. Some amps will support AAC 5.1 bitstream, but many (most?) do not.
    GB Quad Plus, Mut@nt HD51, AX HD61, 80cm dish and Supreme Dark motor. Sony STR-DN 1060, Sony UHP-H1 Bluray, Odroid N2+ (CoreElec), Monitor Audio Bronze 5.1 speakers

  9. #39
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    Quote Originally Posted by fat-tony View Post
    The Miracle Box Twin is a lower specced box so I assume that is why it doesn't have the AAC to DD transcode option in the menu.
    I'm not sure if they have got T2 HD and ACC decoding working correctly on the MB Twin Premium. With many HD programs with 'talking head' content there is definitely a lip sync problem which isn't apparent on SD broadcasts.

    BY the way, the broadcasters are starting to use T2 for SD TV in the UK. I believe its a way of squeezing more channels into the available bandwidth.

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