Re: Outputting Multichannel sound via HDMI - revisited
Re: Outputting Multichannel sound via HDMI - revisited
- Subject: Re: Outputting Multichannel sound via HDMI - revisited
- From: "Simon Thorpe" <email@hidden>
- Date: Sun, 12 Dec 2010 14:46:22 +0100
- Importance: Normal
Brian, Paul, and any one else who thinks that my questions have nothing to
do with a CoreAudio discussion group,
Sorry - I really do think that the question of how you get applications
programmed with CoreAudio to talk to an 8 channel HDMI interface is
relevant. And if the currently available standard software provided with
any new Mac (iTunes, QuickTime Player, DVDPlayer) don't work, it might be
an interesting issue to try and work out what needs fixing. And if it
turns out that you can only do it with an HDMI 1.4 compatible amplifier
(and not v1.3), then an awful lot of pointless programming could be
avoided by making this clear.
Actually, this morning I've just discovered that if you don't use Apple's
DVD player to play DVDs and choose the open source VLC player
(http://www.videolan.org/vlc/ ), then it works fine. Playing back DVDs
with VLC allows you to select the HDMI output (using the Audio Device
option in the Audio menu), and Dolby Surround Sound comes over the 6
channels of the amplifier, even when 8ch24 bit is selected. No problems
with trying to configure AC3 throughput, Perian, Encoded Digital Output
etc etc.
Even more interesting is the fact that Handbrake (http://handbrake.fr/ )
can rip the DVD and generate an mp4 file with 6 channels of discrete soun
(see http://trac.handbrake.fr/wiki/SurroundSoundGuide ). The resulting
files can be played back through HDMI with both Quicktime Player and
iTunes using 6 fully discrete channels.
Very good news. One slight problem is that the files have the video as
well (so a 4 minute song ends up being over 100 Mbytes) and my attempts to
use QuickTime Pro to export just the audio information have not worked.
Anyway, let me again apologise to anyone who thinks that this is nothing
to do with CoreAudio.
Simon
On Sun, December 12, 2010 10:47, Brian Willoughby wrote:
> This list is for discussions of CoreAudio API programming. You seem
> to be bouncing around between application software feature requests
> and API support, or at the very least you do not seem to have a
> clearly appropriate question. Basically, the only question you're
> going to get answered here is whether it is "possible" to do what you
> want when writing a CoreAudio-based program, and how to do it. If
> it's possible, but not currently implemented by the free software
> bundled with Mac OS X, then you need to look elsewhere for feature
> requests as an end user. Apple's mission is not to provide every
> possible feature that end users might want - there are still a few
> opportunities left unimplemented for third-party developers to provide.
>
> A quick check seems to indicate that CoreAudio supports decoding of
> AC3 formatted data. Whether or not this works with multichannel
> sound is one appropriate question.
I'm glad you agree.
> If the answer is positive, then
> perhaps you should try to write a CoreAudio program which pulls AC3
> data from a DVD, uses CoreAudio to decode it, and then sends the
> multichannel data to a CoreAudio-compliant audio device. There are
> various pieces of CoreAudio, such and AudioFile, ExtAudioFile,
> AUAudioFilePlayer, AUHAL, and AUGraph, which are available for this
> task, but I don't think you're going to find a single object which
> handles the combined task of reading AC3-encoded audio tracks from
> DVD and playing them directly to a device such as the HDMI
> interface.
VLC can do it. See above....
> For one thing, DVD audio is interleaved with DVD video
> data, and extracting the audio from the MPEG stream is outside the
> realm of CoreAudio.
>
> This is all fascinating technology, and as an end user I would like
> to be able to play a DVD in surround from my laptop when it is
> connected to any of a huge variety of multichannel audio interfaces,
> but I still recommend that you ask focused questions which are
> relevant to this list. I realize that I have, at times, strayed from
> the CoreAudio topic in my own postings, so please take this as a
> constructive and friendly suggestion.
>
> P.S. I think that Paul used the word "frequency" to refer to how
> often releases appear on the market - I don't think he was saying
> anything at all about 44.1 kHz versus 192 kHz.
OK - I apologise for my misunderstanding.
>
> Brian Willoughby
> Sound Consulting
>
>
> On Dec 11, 2010, at 23:50, Simon Thorpe wrote:
>> On Sat, December 11, 2010 18:52, Paul Davis wrote:
>>> On Sat, Dec 11, 2010 at 12:00 PM, Simon Thorpe
>>> <email@hidden> wrote:
>>>
>>> I was reading along with interest until we got to here:
>>>
>>>> But, now that I can potentially output 7.1 channel audio, I'm pretty
>>>> much
>>>> stuck because of the fact that multichannel audio recordings that
>>>> can be
>>>> played on a Mac are effectively non existent. iTunes will
>>>> happilly play
>>>> multichannel recordings but the only stuff you can buy from the
>>>> iTunes
>>>> store is stereo. Other sources such as Spotify, Deezer etc are all
>>>> stereo
>>>> only. If anyone knows of a place where I can get hold of
>>>> multichannel
>>>> recordings, I'm definitely interested...
>>>
>>> So you're only interest in this is (a) 7.1, a not very good
>>> multichannel format invented primarily to generate licensing revenue
>>> and (b) playing back existing recordings?
>>> What made you think that people release multichannel recordings with
>>> any notable frequency whatsoever?
>>
>> I don't care at all about frequency - at my age, 44.1KHz is
>> probably just
>> fine! No, the problem is that I can't even play the 5.1 Dolby Surround
>> Sound tracks on my DVDs using Apple's DVD player! In the DVD menu,
>> I can
>> choose different audio formats (Stereo, Dolby 5.1 surround sound)
>> but when
>> I've selected 8channels in Audio Midi Setup, it just comes out as
>> stereo.
>> And if I select Encoded Digital Audio, there is no sound at all.
>>
>> Yes, I know that it is (just) possible to output AC3 encoded
>> signals via
>> an optical link
>> (http://www.cod3r.com/2008/02/the-correct-way-to-enable-ac3-
>> passthrough-with-quicktime/
>> ). But this hack doesn't work with the 8channel HDMI option. By the
>> way,
>> I've tried with and without Perian installed (http://
>> www.perian.org/ ) -
>> nothing seems to work.
>>
>> So, let's forget about fancy 7.1 recordings. How about being able
>> to play
>> the hundreds of thousands of DVDs with Dolby surround sound?
>> Currently, I
>> have to use a stand-alone DVD player to play them.
>>
>> It seems to me that having a bit of code built into CoreAudio that can
>> read AC3 encoded audio tracks and play them through the 8 channels
>> available via HDMI is the strict minimum.
>
>
__________________
Simon Thorpe
CerCo, Université Toulouse 3, CNRS
Faculté de Médecine de Rangueil
31062 Toulouse Cedex 9 - France
Tel 33 (0)5 62 17 28 03. Fax 33 (0)5 62 17 28 09
http://www.cerco.ups-tlse.fr
http://www.spikenet-technology.com
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