QuickTime AC-3 Decoder

[TugBoat]

I can't believe how undocumented Surround Sound creation in QT7 is at present. I looked all over Apple, at the HB forum, other places, and it sucks. Well, the last MOV created using the VirtualDM AVI/AC3 didn't work in VLC so I tried something different.

I used A.Pack to Decode the 5.1 AC3 to 6 AIFF channels then placed them into Compressor. I used the QT movie format (video disabled) to create the AAC audio track then simply added that track to the ffmpegX XviD video only AVI I already had. The saved movie works in everything and is seen as having 6 channel audio with the exception of the ffmpegX summary window where it is reported to have only 3 channels.
Whatever....



I later tried the method described on the HB forum using just QT Pro and got a different result. Apparently the channels are not being assigned using the Compressor method, which is strange. And would THIS work to get the sound out of my old TiBook?



I think I'm going to just hang out and see what happens with AC3 on the Mac and probably plan on connecting a computer to the TV instead of a DviX Player....

[sdm]

Tugboat, I'm a step behind you.
I just ran the command line avimerge to merge an xvid .avi with original AC3 soundtrack (direct from MTR)

ffmpegX and VLC report 3 channels, QT reports stereo. Anyways, when I play it through my home theater ... I'm quite confident there is no downmixing.

With both the CLI and D-Vision, the resulting .avi plays nicely everwhere, my only problem is the fast forward scan and regular fast forward on my eyehome isn't what it should be.
i.e. you can't see what's happening as you advance.
I think this is an index problem. I also know its not a problem with other methods of encoding.

Any thoughts on this?

-sdm

[TugBoat]

Yes, I'm convinced that AVImerge is still not muxing the 5.1 correctly. You can use VirtualDubMod for muxing and everything sees the 5.1 correctly. It's really simple, I tell VDM to open the Video only track, then select Video/Direct stream copy, then open Streams/Stream list, and tell it to add the AC3 5.1 track.

After it takes way too long to parse the AC3, I select Save As..., give it a name, and it quickly muxes the tracks. And everything sees it correctly. Come to think of it, none of the Mac programs take such a long time to parse the AC3, maybe that's the difference? I'm afraid that there just isn't a way to correctly MUX AC3 5.1 into an AVI on the Mac at present.

And you can forget about Apple ever Licensing AC3 from Sony. IMHO, that's why they came up with Multichannel AAC, as an alternative to 5.1 AC3. I found a good thread at Apple describing what you need for AAC multichannel playback. I also found where you can get the discontinued M-Audio Sonica and the hard (?) to find Griffin FireWave. I've already ordered a FireWave :P

I also finally used mencoder to encode the video and Passthrough the 5.1 AC3. It does the same thing on my machine. QT says it's fine but then only plays the first second or two of audio then drops the sound and then when you try to use any controls or quit QT, it hangs QT, and you have to force quit QT. This is very similar to what I experienced when I used the old version of ffmpegX (P or Q) to mux the tracks. The only difference is the old version muxing wouldn't hang QT.

Are we having fun yet?

OK, I've got my shades on now (it seems to be very bright in here).
Way too long means about 15 to 20 minutes for a full length movie. This has to be the difference. I don't know why I didn't think of it before. And when you use an external sound system, the way I understand it, the encoded AC3 or DTS stream is passed to the external device and decoded by the external device, not the computer.

[Mildew]

I wonder what Major would have to say about this.

[TugBoat]

Anyone have X11 installed?
I found another App that looks interesting but you need X11 installed on the Mac to run it. I tried the Windows version in VPC and the AVI it Muxed worked fine in everything.

But...

The App itself says my input 5.1 AC3 is only 5 channels, not 5.1 or 6. Then when you load the output into ffmpegX the Summary window says it's 5.1 but the Info button says 5 channels and VLC agrees, 5 channels, not 6. Well, I guess 5 channels is better than 3 8)

It's here;
http://avidemux.berlios.de/index.html
It's also here;
https://www.videohelp.com/tools?tool=AviDemux

[DeusExMachina]

Perhaps the original never actually had an LFE channel, but just let the sound system interpret it? Even if it was listed as 5.1, the original might have only had Left Front/Rear, Right Front/Rear, and Center channels. That might explain some of the other odd behaviour. Perhaps there is an application that will let you separate out the channels and listen to/watch them individually; that way you can see what the LFE track on the original is doing. You could also analyze the output file to see if it is sending anything to the .1 LFE channel, even though it is not showing up.

[sdm]

Tugboat,

Well, it seems pretty sad that AC3 audio is so poorly supported on OSX. I begrudgingly decided to try PC apps in Virtual PC.

I gave VDM a shot in Virtual PC. I did what you said, and got to the save as part. A few seconds into the save, VDM gives me a runtime error and quits. I suspect I may not have everthing installed properly. Any thoughts about this?

I didn't want to install X11, so I'm also trying AVIDemux in Virtual PC as well. Will report back soon.

-- sdm.

[TugBoat]

I don't think it's my source file. A.Pack , mAC3dec, and a52decX 0.24 all say it's 6 channels. And if I decode it, I get 6 AIFF files. It's also the same source file I've used in around a dozen other tests. No problem, I'll rip another copy off the DVD and report back if there are any changes.

[sdm]

Well avidemux fixed the Fast forward and fast advance!

I'll be interested to hear more. I'll sit back and watch.

-- sdm.

[DeusExMachina]

FYI, AVIDeMux has some "Issues" in X11. Several of the options crash it, but in general it seems to work OK.

[TugBoat]

I can't help you much with Windows runtime errors
I installed a GordianKnot package into XPpro SP2 and ended up with VDM 1.5.10.2 build 2540. About the only thing I use it for is Muxing and I've never had that error.

I was having problems trying to save to a networked volume at first and had to save to inside VPC, but it was a permissions problem and I 've fixed that

I hear Major is working on a ffmpegX update....

[TugBoat]

...FYI, AviDemux in general it seems to work OK...

I'm getting the same results with the newly ripped 5.1 AC3 in the 2.1.2 PC version of AviDemux, 5 channels. Does the Mac version list the source correctly? Everything else I have says the source is 5.1, 6 channels.

It appears to be another Labeling/Muxing problem. I can extract the AC3 file from the AviDemux AVI, that everything says is 5 channels while in the AVI, and then it magically becomes 5.1/6 Channels again outside of the AVI. I would suppose that if the AVI was played with a computer that had an external surround sound system the encoded stream would be passed to the Sound system and be decoded/played correctly. Add another to the list.

[TugBoat]

...Anyways, when I play it through my home theater ... I'm quite confident there is no downmixing...

I'm still confused about QT and 5.1 AC3. Can you tell me if you are indeed getting QT to pass thru 5.1 AC3 via an Optical connection to your Sound System and that the Sound system is acknowledging receiving 5.1 AC3? Have you tried playing a QT 5.1 AAC over the same system and is the Sound System acknowledging 5.1 Surround from the AAC stream?

You might look at this thread at Apple as it's why I'm asking these questions, you can even post your response there if you wish, I'll see it
http://discussions.apple.com/thread.jspa?messageID=2576055#2576055

[sdm]

Hi Tugboat.

No I'm not using Quicktime to play on my home theater.
I'm using an Eyehome (the box decodes the media files itself-including ffmpegX's passed thru AC3).
The Eyehome is connected to a Kenwood reciever thru an optical cable.

Sorry.

-sdm.

[TugBoat]

So, I got the FireWave yesterday, been playing ever since

I'm still not completely familiar with it, but I'll note a few observations.
First, for the moment, I'm using three stereo systems for Speaker output. I'm still investigating on which 6 channel receiver I want. Really, all I need is 6 powered speakers. The FireWave has three mini-stereo ports for outputting the 6 channel discrete audio so each stereo system is plugged into a miniport on the FireWave. A quick volume adjustment on each system and all is well.

I set the MIDI Control for the FireWave and configured the Multichannel Speaker setting for 5.1 Surround. The FireWave comes with an App that allows it's own Surround Mode (Discrete or Dolby Pro Logic II), Speaker Config., Volume Adjustment, and Noise Generator for Speaker Arrangement. According to the Speaker Arrangement test, the speakers are correct for Discrete and Pro Logic II.

First test, I want to see how the new A52Codec.component (QT AC3 Plug-in) works. As I suspected, the Plug-in will not allow QT to pass AC3 audio to the FireWave. I tested AVIs with 5.1 and 2.0 AC3 tracks, the plug-in uses the computer to play 2 channel audio only. When the FireWave is in discrete mode, I receive audio only from the left, right and LFE Speakers. When I switch the FireWave to PL II, I get audio out of all 6 speakers. Oh well....

Next I switch to VLC. Nice. VLC will pass the AC3 to the FireWave and play 5.1 AC3 very nicely. When I try 2.0 AC3, I again have to switch to PL II to receive audio from all 6 speakers. A very nice side benefit, since the FireWave is decoding and playing the Audio, the computer only uses half of the processing power to play the movie. Very nice on old computers such as my 667 TiBook. It's nice to see the processor at 40-50% instead of 60-80%.

DVD Player works as expected. The AC3 track is passed to the FireWave and sounds great.

Now to the 5.1 AAC tracks. The movies I tested (I made a few myself) sound just as good as the 5.1 AC3 AVIs. Unfortunately, my old TiBook runs up to 70-90+% processor usage with just Standard 5.1 AAC XviD/DivX movies. High Def. is hopeless on the TiBook, but, the only HD movies I've seen are the Apple trailers...I don't watch those anyway.

So, at this point, VLC wins the 5.1 battle. Most 5.1 Movies you run across are going to have 5.1 AC3 and using only half of the processor power to play them is a big plus. I guess by the time I replace the TiBook with a Core Duo there might be more AAC 5.1 movies around, but until then my collection is going to remain AC3 audio when possible.

My thoughts, Apple should just bite the bullet and License AC3 (DD) for QuickTime. Dolby has been around for a Long time and is not going to go away anytime soon.

[sdm]

I've got an update for this topic.

to refresh your memory...

I have encoded 50+ videos to AVI (Xvid+AC3) using ffmpegX with mencoder to encode video, and passthrough for the audio.

Contrary to many people's opinion, the audio retains the 5.1 channel surround sound (but is downmixed to stereo when played using QT player)

These AVIs play in VLC, Mplayer and my home theater.

When playing the AVI in QT I had to use AC3Codec 0.3 to have them play. This is a buggy component that flakes out and loses sync if you move the playhead arround on the timeline.

Then a new QT component came out a52Codec 1.5 that started this thread. I reported QT wouldn't play the AVIs in question.

I'm happy to report that the newest version a52Codec 1.7.2 finally allows QT to play these files - Flawlessly!!!

A second discovery has to do with FFmpegX creating AVIs that were several days long, with only the first 2 hours being the movie, the rest, a blank white screen. This occured when encoding an avi with ffmpegX using ffmpeg as the video encoder and passing through the audio.

The discovery is that the new codec Perian 0.5 allows QT to see those videos as the correct length and plays them properly!
I still can't recommend enoding avi (xvid or divx + AC3 passthrough) using ffmpeg encoding because the files it produces don't play properly in vlc, mplayer etc.

Enough rambling, I hope this report is interesting to some.

-- sdm