Now if only we could get surround sound audio passed through to AV amps as well ... I'm not even looking for transcoding to DD. I'd settle for multi-channel PCM which is what the PC seems to do quite happily normally.
I've just tried editing a Freeview HD .wtv recording with a surround sound audio track, using the latest beta release from VideoRedo. This edit has stripped the LAOS/LATM headers leaving AAC-LC 6 channel ADTS, which is supported by the default MS Audio Decoder according to MSDN.
I was hoping for 6-channel LPCM output, but even playback of this edited .wtv is downmixed to 2.0 stereo over the hdmi link to my amp. It's very frustrating as I can bitstream TrueHD and DTS-MA from other media such as mkv's using the same 7MC setup.
Has anybody tried extracting the aac decoder from the Windows 8 CP to see if it can output anything other than stereo in windows 7?
I had a very quick play the other day because i noticed it was a new version and didn't get any audio at all from the hd channels using the new version. But all i did was a file replacement. I don't know if there are any other hacks that can be done to get it to work.
The other thing i haven't got aroung to trying yet is tuning to a freeview hd channel from within w8 itself. But I think that would mean installing w8 onto proper hardware rather than using a vm.
I've installed Win8 on hardware - still only stereo output when tuned to the Freeview HD channels unfortunately. I posted it as a question on the MS Answers forum: answers.microsoft.com/.../55a7e44f-6b1d-43a3-93be-4ccc00f89907
Thanks for the link to MS Answers. I've added my 2pence worth, but I'm not sure how effective this be, especially if it's not addressed in the WIndows 8 Consumer Preview version of Msmpeg2adec.dll
The lastest decoder documentation at msdn.microsoft.com/.../dd742784(v=vs.85).aspx still explicitly excludes support for LATM/LAOS.
Wow, after all this time I think I accidentally stumbled upon a workaround. For whatever reason, my receiver and PC didn't play nicely together when I switched them on today, and I was getting no sound over HDMI, so I just flicked the receiver onto a different source, then back to PC which got it going again - with the added bonus of proper 5.1 sound! (I was watching BBC1 HD at the time). It even worked on the other HD channels, and the 411-more info screen showed "PCM" as the output type rather than the usual "Matrix-encoded PCM stereo." However, as soon as I stopped TV playback and started it again, it was back to the usual stereo output only. After searching the net for a bit, I discovered a way to get my 5.1 sound back again - by disabling "Exclusive Mode" which can be found on the Advanced tab of the HDMI audio device properties window.
The Exclusive Mode setting appears to be required to allow an application to transmit encoded data to the receiver. By disabling this setting, the PC now decodes ALL audio and transmits it as multi-channel PCM. This works great, provided you have configured the speaker settings as 5.1/7.1, and aren't too worried about the PC decoding everything. This is fine for me - better actually, as I no longer lose those few seconds of audio when pausing/resuming playback of a video with AC3 audio due to the receiver switching modes.
So I think the upshot of what was happening with the Exclusive Mode setting enabled is that since media centre couldn't output the AAC stream to the receiver directly, it was for some daft reason not bothering to transmit it as multi-channel PCM either. Disabling the setting appears to take the responsibility for output away from the application and give it to Windows instead.
With regard to the LAOS/LATM headers - these are now supported in the AAC decoder in the Windows 8 release preview - but I don't think the lack of support for these was affecting multi-channel audio at all, for two reasons. Firstly, the audio was actually being decoded fine - it was just the output that was messed up. Secondly, according to this post from the BBC: www.bbc.co.uk/.../questions_around_surround_soun.html the main audio is coded as AAC/LC and it's only audio description services using HE-AAC. I'm guessing that not supporting the LAOS/LATM headers would prevent you from receiving the audio description services, but not the main audio.
Hopefully this works for someone else too.
I may be completely mistaken, but I thought LATM headers were applied to the AAC-LC main audio. More importantly, in the light of your very interesting results with WIndows 8 Release Preview, I wonder if anyone has successfully copied the updated dll onto a Windows 7 Media Centre system?
Sorry if it was a bit unclear in my previous post - I have this working on Windows 7 out of the box - just disable the "Exclusive Mode" setting in your HDMI audio device properties, and enjoy 6 channels :)
You're right that disabling exclusive mode will ensure that LC-AAC 5.1 is decoded on the PC and output over HDMI as 6-channel PCM. But (at least for me) it doesn't bitstream HD audio formats which I want my amp to decode. And it doesn't handle DTS-MA at all. So for 7MC, I'm stll setting exclusive mode and using a Neural setting on my amp for Freeview HD, to simulate 6 channels from LPCM matrix encoded stereo. That way I still have HD audio bitstreaming from Blu_ray media.
i take it you're not interested in codecs? because i bitstream DTS to my amp using Shark007's codecs very easily
Thanks for the tip. I'm already using ffdshow (rather than shark007) for bitstreaming audio. It's just that this requires me to use the 'enable exclusive mode' setting on audio configuration, which has the unfortunate effect of breaking the audio decoder output from Freeview HD LC-AAC broadcasts. As posted by PLePage, above, LC-AAC gets decoded to matrix stereo in this case, rather than discrete 6-channel PCM - which would be preferable.