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80 posts

Master Geek


Topic # 22513 30-May-2008 06:56
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Hi all,

In case anyone else hasn't noticed, I discovered several days ago that TV3 (DVB-T) was broadcasting with AC3 audio in additional to the normal AAC stream. And, as of 6:49 am this morning, they are still doing so. I'm using DVBViewer 3.9.2.0, by the way.

So far, I've only been able to get the freeware AC3Filter to decode the AC3 stream. However, I do have the Cyberlink PowerDVD 8 codecs on my system - which should handle AC3, if I read the Help correctly.

AC3Filter is available here: http://ac3filter.net/projects/ac3filter

Peace


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  Reply # 134340 30-May-2008 08:31
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Just did a scan and found the ac3.




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  Reply # 134400 30-May-2008 11:29
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Eyetv is also picking it up.

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  Reply # 134409 30-May-2008 12:17
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is it 5.1 with a center channel or just stereo?




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Master Geek


  Reply # 134411 30-May-2008 12:31
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According to the AC3Filter Level readout it's just Stereo at the moment. That might be due to the source material though. I'd assume we wouldn't hear true 5.1 until TV3 broadcast a source with it encoded - like a Hollywood movie.

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  Reply # 134419 30-May-2008 12:47
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did a rescan and got the same off Wharite.  Can't test it, as not at that PC for the moment.

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  Reply # 134501 30-May-2008 19:18
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geekiegeek: is it 5.1 with a center channel or just stereo?


recording info from Media Info says the following

Audio #1
ID : 410 (0x19A)
MenuID : 1300 (0x514)
Codec : AC3
Bit rate mode : CBR
Bit rate : 384 Kbps
Maximum bit rate : 432 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Rear: L R, LFE
Sampling rate : 48.0 KHz
Video0 delay : -958ms
Language : English


there is also still a AAC channel in there too.  With the lack of software support, I can't actually check if both have audio at the moment.

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  Reply # 134512 30-May-2008 19:46
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Maybe now someone will post some more samples with the AC3 audio so that we can try them out with say our Popcornhours  which won't play the AAC stuff..




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Old3eyes


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  Reply # 134515 30-May-2008 20:07
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It appears to just be a stereo AC3 feed, the same as they were transmitting for months before the official launch.

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  Reply # 134677 31-May-2008 20:55
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its a stereo feed rebroadcast in a 5.1 container. presumably when a program has 5.1 sound the other channels will be used. i guess they didn't want to have it so the ac3 appears and disappears everytime a program has it. It would have been nice of them upmix the audio to 5.1 so the other channels aren't wasted bittrate.

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  Reply # 134741 1-Jun-2008 12:49
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More specifically its Left and Right channel audio only ie the center channel is empty - which IMO sounds really bad on a 5.1 system.  I'd rather have the centre channel only, for non DD sources.
 
Interesting that the Vista MCE beta correctly interprets the DD (complete with little DD logo on the info panel) sound track and defaults to this over the AAC soundtrack ie no need to manually select the AC3 soundtrack, which will be nice once its stable enough to use.  Records it as the default soundtrack as well.







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  Reply # 134745 1-Jun-2008 13:10

Can someone check tonight with CSI (8.30) to see if all 5.1 channels are broadcasted (this should be HD Video/5.1 Audio source)

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  Reply # 134810 1-Jun-2008 20:39
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cranz: Can someone check tonight with CSI (8.30) to see if all 5.1 channels are broadcasted (this should be HD Video/5.1 Audio source)


Still L+R audio only.

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  Reply # 134836 2-Jun-2008 00:41
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Well no reason to complain. Before we had one option, now we have two.

But CSI sounded fine to me through both the aac and the ac3.

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  Reply # 134864 2-Jun-2008 09:54
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This thread says that the movie J Parkwas AC3  5.1..

http://www.dtvforum.co.nz/forum/showthread.php?t=348





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  Reply # 134893 2-Jun-2008 11:50
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talsemgeest: Well no reason to complain. Before we had one option, now we have two.

But CSI sounded fine to me through both the aac and the ac3.


Well IMO I still struggle with why this is so hard to get right...

You can jump onto bittorrent and download any of the US primetime shows in HD and with AC3 soundtracks attached.  These are correctly encoded and use all 5.1 speakers just as they should.

This isn't a new codec, its been around for 13 odd years, and has been used by broadcasters worldwide for years.

Broadcasting 2 channels, in a 5.1 channel stream just doesn't cut it IMO.  Especially when most of the shows currently broadcast in HD on TV3 already have a broadcast AC3 soundtrack in the US.

The problem is, is that unless you re-matrix the sound in your amp (which defeats the purpose of AC3 in the first place), you only get the left and right speakers working.  IMO Left and Right only in an AC3 stream sounds terrible. 

Currently the AAC stream sounds better, simply because the voice channel stays in the centre where it should be.

Maybe theres a huge raft of technical issues which I'm missing.



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