Re: AC3 encoded output
Re: AC3 encoded output
- Subject: Re: AC3 encoded output
- From: Jeff Moore <email@hidden>
- Date: Wed, 13 May 2009 14:58:26 -0700
It seems like you have answered your own question. The first task is
to get your data encoded into an AC-3 stream. We don't ship anything
like that on the system, so you probably need to get in touch with
Dolby.
Once you can produce the AC-3 data stream, getting the data out of the
machine uses the same pass-through support in the HAL that the DVD
Player, VLC, and others use to send AC-3 data out the SPDIF interface.
Basically, this amounts to setting the format on the digital out
stream to kAudioFormat60958AC3, and then providing the AC-3 data
(transformed according to IEC 60958) one packet at a time via your
IOProc.
I don't think we can help you much with the first task, but we can
certainly address any additional questions you might have about the
second.
On May 13, 2009, at 2:00 PM, Stéphane Beauchemin wrote:
We have an application that supports stereo and surround (5.1)
setup. Most of the mac hardware (if not all) have digital output. It
seems that there is no way to output AC-3 encoded audio to the
digital out with core audio. I have done quite a bit of research and
it seems that we would have to implement the AC3 encoder ourself.
We know that we can set the speaker config in "Audio Midi Setup" to
5.1 surround, but it assumed that the sound card has 6 discrete
channel. This is only available on the pro audio soundcards.
Our data, is 32 bit PCM float. With a DVD stream poeple just
implement a passthrought... but here it is not the case. We need to
generate AC3 data at run-time. Any suggestions?
--
Jeff Moore
Core Audio
Apple
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