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Thread: Dolby 5.1

  1. #16
    adm's Avatar
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    Quote Originally Posted by Rob van der Does View Post
    No: Ocram is down. Just rename the Ocram file in /etc/opkg for the moment and try again.
    I changed the name and after a reboot of the box the list of plugins was downloaded.
    'automaticvolumeadjustment' is not in the list. From memory, the downloaded list seems to be identical/similar to that I've seen before and is much shorter than detailed in some of the posts on this site for other boxes/images.
    Perhaps that is not compatible with the VIX image or not compatible with a box configured for terrestrial TV tuners???
    A Google search for the plugin resulted in some sketchy instructions in English. With no first hand knowledge, it appears that it is to balance channels and maybe assumes that the coding doesn't change between individual programs.

  2. #17
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    automaticvolumeadjustment is available on the ViX feeds for my boxes.

    Help asked via PM will be ignored.
    The forum is there for help and all will benefit from your questions.
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  3. #18
    darucla23
    The UK Freeview+ HD standards mandate the use of AAC-HE for broadcast use, to accommodate the sight-impaired voice over track. All Freeview+ HD compliant pvrs, like the Humax, have to transcode the AAC 5.1 signal to DD 5.1 for output via either spdif or HDMI. The signal recorded on the disc is still AAC. So if you transfer to to an external store. like a NAS or PC, you will have a file with AAC 5.1 audio. Devices like the popcornhour will output these files with 5.1 LPCM over HDMI (I have not tried spdif, but I suspect it won't work). My Pioneer SC-2022 AV receiver will handle those 5.1 LPCM channels quite easily, but it will not handle 5.1 AAC at all. I do not know of a receiver that will. So, to use the 5.1 sound from a Miraclebox, I need to copy the file to PC, and/or play it with my PCH. Otherwise, it needs to be mixed down to stereo in the MB settings.

    If the Miraclebox could transcode the signal to LPCM, like the PCH, that would be very useful. It would be even better if it could transcode to AC3 5.1, but I expect there are problems with this.

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  5. #19
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    I have not been able to get 5.1 LPCM over HDMI from either the MB or my Quad Plus. I'll qualify that slightly - if I try to play 5.1 LPCM it seems to be mixed down to two channels. I'm assuming it's a shortcoming of either the hardware in these boxes or else an issue with multichannel audio in enigma. For sure S/PDIF does not support 5.1 LPCM - you need HDMI for that.

    Interesting that the Humax terrestrial HD box will transcode multichannel AAC to AC-3.
    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

  6. #20
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    I can't imagine any hardware to provide support for specs that deviate so much for just a few services.

    Help asked via PM will be ignored.
    The forum is there for help and all will benefit from your questions.
    NO CARD SHARING TALK WILL BE TOLERATED, LAN OR WAN, IN OPEN FORUM OR PM !

    English is not my native tongue.
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  7. #21
    darucla23
    The LPCM transcode works on the PCH A200 from some years back, as well as the newer models, so I suspect it is not very taxing on the processor.

    I also believe that more countries will go to using AAC on terrestrial services. In fact I'm pretty sure that we're not alone already. Much of Europe is changing to T2, with H264, as the phone companies take up more and more bandwidth. We've already given up channels 61 - 68, and the channels above 50 are now under the cross-hairs.

    As I said, *all* Freeview+HD licensed boxes (and others like Youview, which is not technically Freeview+) in the UK have to include the AAC to AC-3 transcoding, not just the Humaxes. A couple of boxes were launched very early which did not do this, as the requirement had a cut-off point, but those boxes are no longer on the market, having vanished along with their companies. The majority of TV watching in the UK is terrestrial.

    I see this coming up in various video related forums lately, so I think it is becoming widespread.

  8. #22
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    Back to the original question.

    Ignoring the SPDIF link, what comes out of the HDMI socket when the box is receiving a UK HD terrestrial broadcast with surround sound?

    With no downmix is it 5.1 AAC?
    With downmix is it 2 channel PCM, 6 channel PCM or something else.

    If I cannot get surround sound without spending mega amounts on new equipment, which even then may not support the MB "5.1" output directly, at least I have the option of spending another 60 quid for two satellite tuners and converting my box to a satellite (Freesat) PVR with HD capability - assuming the MB supports a 7 day Freesat EPG .

  9. #23
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    I've had no luck with getting six channel PCM over HDMI out of my Quad Plus. Seems to downmix to two channels. The ViX image on any receiver will generate a 7 day EPG from Freesat.
    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

  10. #24
    darucla23
    I am pretty sure that if no downmix, it tries to output 5.1 AAC, which nothing will decode. With downmix, it outputs 2.0 AAC, which almost everything can handle.

    In either case, you cannot get multi-channel.

  11. #25
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    Quote Originally Posted by adm View Post
    Another observation

    There is a difference in volume level by a (hearing) factor of 2 when tuned into a HD channel between HD programs with surround sound and HD programs without.
    There is an AutoVolume(?) plugin that might help. I've installed it and will see whether it works for FreeviewHD.

  12. #26
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    Quote Originally Posted by birdman View Post
    There is an AutoVolume(?) plugin that might help. I've installed it and will see whether it works for FreeviewHD.
    I've now found the same. It appears that the size of the list of plugins I was getting depended on the name I gave to the renamed orcam file. Deleting the file completely now gives me the full list.

    The set-up only refers to DTS/AC3 decodes not AAC needed for UK HD Freeview.

    Now we have to wait for a known surround sound broadcast, possibly a Channel 4 HD modern(ish)film, Big Bang Theory on the same channel or one of the flagship programs on the BBC this weekend.

    Edit - On playback of a recording where there is a transition between non-surround and surround sound it makes no difference in the 2:1 change of volume irrespective of setting in the configuration file for the plug-in. The plugin is probably not detecting the difference between aac2 and aac5.1.
    Last edited by adm; 02-10-14 at 00:54.

  13. #27
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    Quote Originally Posted by adm View Post
    The set-up only refers to DTS/AC3 decodes not AAC needed for UK HD Freeview.
    But that might be addressable by changing the source code of the plugin to check for AAC as well?

    Specifically this at line 162:
    Code:
    	if "AC3" in description or "DTS" in description:
    Last edited by birdman; 02-10-14 at 01:50.

  14. #28
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    Quote Originally Posted by birdman View Post
    Specifically this at line 162:
    For interest, where did you find the source code?

  15. #29
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    Quote Originally Posted by adm View Post
    For interest, where did you find the source code?
    The text "the source code to the plugin" is a link to it...although I agree that you can't really tell from the appearance.

    Three sites of interest are:(so those three items are links too) but don't ask me about the differences between the first two (they are not all that similar), and don't expect to find any documentation of useful information at any of them either.
    Last edited by Rob van der Does; 03-10-14 at 05:04. Reason: Better lay-out for links

  16. #30
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    @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.

    As regards AAC and DD compressed streams - my Quad Plus will pass bitstream DD 5.1 over HDMI or S/PDIF with no issues. It will also convert DD 5.1 to six channel PCM 48kHz output over HDMI if I have the multichannel option set (and also no Dolby downmix). If Dolby downmix is set you get two channel PCM output irrespective of how many channels are in the Dolby bitstream. If Dolby downmix is set, you don't get the multichannel option in the menu.

    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.
    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

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