Re: SPDIF encoded output on G5
Re: SPDIF encoded output on G5
- Subject: Re: SPDIF encoded output on G5
- From: Derk-Jan Hartman <email@hidden>
- Date: Thu, 1 Dec 2005 18:32:48 +0100
I have DTS working again as well.
Now I just have to merge our auhal and coreaudio module so that we
use AUHAL for non-encoded audio and coreaudio for encoded digital
signals.
I'm very grateful for everyone's patience and assistance over the
past 2 years. I couldn't have done it without you all. (or without
the G5 donated by the users for that matter).
DJ
On 1-dec-2005, at 1:09, Derk-Jan Hartman wrote:
Incorrect. You need to byte-swap as dictated by the flags.
Natively, an AC-3 bitstream has the same endian properties as
MPEG data streams. That is, it's big endian. When you take the
native stream and hack it up to be put on a SPDIF cable (which is
what kAudioFormat60958AC3 signifies), you are basically making
the AC-3 packet behave like 16 bit, stereo, signed integer data
(which is why the standard format flags apply to the ASBD).
So, if the ASBD sets kAudioFormatFlagIsBigEndian, you don't need
to byte-swap. If kAudioFormatFlagIsBigEndian is clear, you have
to byte-swap the data as if it was 16 bit samples.
mm, ok.
This is extraordinary in my eyes. I have not seen a device so far
that has big endian set for SPDIF output in HAL or Alsa.
In this case does the SPDIF header have to be byteswapped as well ?
Answer to self,
YES you do.
I made some changes to the VLC framer to output big endian, and now
it works !!!!!
wohooo. the question now is how i nicely integrate this into the
VLC architecture. Alsa is always LE as far as i know, but from
DirectX i'm no so sure. Depending on the commonness of this i will
either byteswap back in IOProc or introduced spdif_LE and spdif_BE.
but that's for tomorrow.
Finally after all this time, VLC will be able to support digital
audio and discrete multichannel audio in one application. :D It
took a while, but we are finally there :D
DJ
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