AirPlay 5.1 surround

[Aindreas Gallagher]

apropos of nothing – I had to output a 5.1 mix handed off to me as a pass through with an edit in PPro6 for an E3 game trailer a bit back there.

The degree to which I had no idea what I was doing there in PPro is hard to describe. Still haven’t a clue with half of PPro.
I have literally never hugged the internet harder.

https://vimeo.com/user1590967/videos http://www.ogallchoir.net promo producer/editor.grading/motion graphics

[Jeremy Garchow]

I am also using Pr to check all these test files I am making, but also I used AME to try and get a compressed file that I need and AME encodes the files as stems (6 discreet mono).

This is fine if the receiver knows what to do with it, but I am trying to make the lowest common denominator file. 🙁

Premiere’s different types tracks drive me really insane sometimes as they can be difficult to map and monitor. But sometimes, they are A-OK.

Jeremy

[Aindreas Gallagher]

[Jeremy Garchow] “Premiere’s different types tracks drive me really insane sometimes”

oh god yes. Mine was late last minute with the pro tools lady kept to check the output. PPro will actually clean pass through and output a 5.1 though. As ever depends on the sequence setup thing. You can’t monitor it without a track submix for preview mind you. I’m a moron on audio but you can actually get fond of the track mixer apparatus. lots of things going on there?

aside from that tho – the basic inability to set source monitor audio db that carries through onto the timeline? You what?
(you only get a one off +- gain dialogue box thing? Doesn’t carry through? surely not kids.)

Or I’m stupid on that. I’m poking at it. Also absolutely no audio source keyframing represented.
Audio source seems a bit of a wasteland.

https://vimeo.com/user1590967/videos http://www.ogallchoir.net promo producer/editor.grading/motion graphics

[Michael Gissing]

From the viewpoint of audio deliverables for broadcast the term stem specifically applies to the separate elements that make up the mix. Music, Narration, Dialog and Effects are considered the typical stems. They can be mono, stereo , 5.1 or 7.1 . The term really means mix components and is not used to describe the mix or DME. When I hear people describing Roles as stems I cringe as roles best describe routing – bussing or sub grouping as it is described in the DAW world.

Sometimes I am asked to split the effects stems further into foley, atmos & sync fx. Nat Geo like this further stem split. The stem files are delivered as wavs and not usually part of a quicktime file or HDCamSR tape as basic stems need 4 x 6 channels. That on top of full mix 5.1, mix stereo, DME 5.1 & stereo adds up to 48 channels.

To your question Jeremy I use Avidemux(GTK+) software to mux the ac3 to any file. So there is no recompression or format change. This is free Linux software and it enables me to remove an existing audio track and remux any other audio track including ac3. I have subler but haven’t used it since finding Avidemux. It is much like Quicktime Pro but works for mp4 and lots of other formats.

[Jeremy Garchow]

[Michael Gissing] “To your question Jeremy I use Avidemux(GTK+) software to mux the ac3 to any file. So there is no recompression or format change. This is free Linux software and it enables me to remove an existing audio track and remux any other audio track including ac3”

Thanks, Michael.

It’s sounds just like Subler. As far as I can tell, there’s no format change there either, besides the wrapper. Is that right?

For non AC3 devices, do you also add an AAC stereo track below it?

Does that even work? I didn’t get to testing that part today.

[Michael Gissing]

Avidemux lets you add mulitple audio formats so in theory yes to both ac3 and aac. Usually I am getting rid of the aac and replacing with ac3.

In my case I had a specific requirement for a museum display which only needed ac3.

[Jeremy Garchow]

Thanks, Michael.

Ac3 is playing fine on surround systems, but obviously is playing weird everywhere else. On was hoping for a magic setting to have ac3 or AAC depending on device.

I did some reading and it seems like it may be possible, but it may be not worth it, either.

Subler will allow it, but I’m not sure if every device will understand it.

I’ll try it tomorrow.

Thanks again.

[Michael Gissing]

Every video player on the planet should be able to do a standard foldown from 5.1 to stereo so the ac3 should work regardless. Otherwise the risk is the player will not be able to chose or will try to play both audio streams and mix them.

A good player like VLC should allow the user to chose the appropriate track but that doesn’t make it idiot proof as the operator will need some knowledge.

[Jeremy Garchow]

[Aindreas Gallagher] “You can’t monitor it without a track submix for preview mind you.”

But it doesn’t always work. I can’t mix down an 8 channel output sequence to stereo monitoring and keep any sort of channel assignments, for instance. This is one of the things I loved about FCP7 is that you could map any track at any time to any output channel. Pr forces a new sequence, setup just right, with really crappy mapping. If I want an 8 channel output, monitored in stereo, there aren’t enough submixes in the world to get it done as every time I switch back from the submix, my output channel assignments are blown. Then I have to remap and delete the submix.

It drives me nuts. I do like the idea of the submix system (media 100 had it over 10 years ago when I used it), but it doesn’t work like a submix on a real live audio mixer works. I am far from an audio expert, I just know how I want things to work.

The “down mix” button in FCP7 was a very elegant solution.

[Aindreas Gallagher] “aside from that tho – the basic inability to set source monitor audio db that carries through onto the timeline? You what? “

Yeah…perhaps in CC v2? 🙂

[Keith Koby]

I skimmed through the rest of the replies, and don’t think you’ve got this answered yet. Export your 5.1 master ProRes file from your fcpx timeline. Open it in QT to make sure that it is indeed 5.1 in metadata.

Download Handbrake (and VLC). Handbrake started reading ProRes files a while back. I imagine the decode is going to 8 bit, but the resulting h.264 is anyway, so don’t worry.

Grab the AppleTV3 preset and then modify the audio settings to just make the one AC3 5.1 track.

The x.264 encoder in handbrake is ridiculously good compared to just about every paid transcoder out there and the audio will be 5.1.

Not to talk bad on episode, but even if you do get the pro audio option, you have to use the channel mapper to rearrange audio into the order they expect (which by the way matches no industry standard).

Keith Koby
Sr. Director Post-Production Engineering
iNDEMAND
Howard TV!/Movies On Demand/iNDEMAND Pay-Per-View/iNDEMAND 3D