Rendering surround audio for DVD and cinema - help required

peter-sieben wrote on 10/30/2018, 2:34 AM

Goodmorning everybody,

I'm at the final stage of preparing a DVD for a short filmopera. The final sounddesign has been done at a filmstudio, their dynamic 5.1 mix consists of six seperate AIFF 24-bit mono audiofiles, that have rather loud peaks within the allowed digital spectrum (no clipping, peaks go to almost 0 dB). I want to produce a 5.1 AC3 file with Vegas Pro (I've still got the older Vegas Pro 12 on my system that allows me to render to AC3). I do not have a surround monitoring system, only a stereo playback at my home studio.

What is the most safe way to load the AIFF files in Vegas with a 5.1 audio setting and render them to 5.1 AC3? My concern is the volumes and the panning towards the 5 different angles within the surround stage (LFE goes to LFE).

1.) Should I pan each file (L, C, R, Ls, Rs) 100% to their own corner in the surround panner and mute on each track the other 4 corner speakers in that specific panner? When I do this, the AC3 file sounds very loud, the waveform in DVD-Architect shows a loud profile. Or should I lower the volume of all 5 tracks, and if so, how much dB would be safe? Are there any other settings I should look at?

2.) Is the stereo audio-playback mixdown in DVD-Archirect, when previewing a dvd, representative when a 5.1 AC3 file is used? It sounds not very accurate, things are panned strangely, but that could be the result of trying to listen to a 5.1 file on stereo.

Looking forward to any practical suggestions, thank you so much.

Peter

 

Comments

Former user wrote on 10/30/2018, 7:06 AM

Do not do 5.1 mixing without being able to monitor it.

alternative: have the soundesign studio send you a final 5.1 mix.

peter-sieben wrote on 10/30/2018, 3:18 PM

Hi David, thanks for replying. I don't to mix it myself, that has already been done. I only want to encode their 5.1 mix (delivered to me as 6 mono-aif files) to AC3 for DVD in a save way. Would that be posssible without having to monitor it in 5.1?

Former user wrote on 10/30/2018, 5:17 PM

It is possible, but I wouldn't release it until you were able to verify on a 5.1 system. Do not pan anything. Just mute the channels. For example,if it is FRONT LEFT, mute all others. If you move the panner as well, it will increase the volume. I have a 5.1 home system hooked up to my computer so I can verify the channels and LFE. If you plan on doing more of this, I highly recommend this as a minimum.

peter-sieben wrote on 10/30/2018, 6:18 PM

Many thanks for the advice not to pan anything, you are right about changing the volume when panning into the 'corner' for each track (and per panning window muting the other speakers etc.). The first 5.1 AC3 rendering sounds balanced on stereo playback, nothing sounds odd in the mixdown. I'll do some more testing.  

Are you able to reproduce this way of work with your set-up and surround speakers?

Former user wrote on 10/30/2018, 7:21 PM

Yes, in the past I have been given 5.1 mixes as mutitrack and I muted and got the mix close to what I think was the original final mix. I did pan one time and the audio person complained that the volumes were not correct.

peter-sieben wrote on 10/31/2018, 2:03 AM

After some more testing I feel confident enough to add the 5.1 mix in AC3-format to the DVD via Vegas/DVD-Architect, there will also be a 2.0 stereo mix on the the DVD that has been provided by the filmstudio. A big thank you for your help!

Apart from the DVD, we also produce a DCP for playback in cinema. The six 24-bit/48 kHz AIF-files from the filmstudio and the operafilm (edited by me with Vegas) are combined to a DCP using DCP-o-Matic (freeware DCP-software). With the DCP-creation I was also worried about the volume of the AIF-files, I've lowered all tracks with -6 dB and will have a test playback of that DCP at a local cinema today. I'll ask the cinema if they also can test play the DVD with the 5.1 AC-encoding.

ChristoC wrote on 10/31/2018, 4:46 PM

Musicvid kindly posted this years ago, for use with the Vegas AC-3 PRO encoder: my experience is his advice works very well.

I've run some exhaustive tests with calibration test tones and done extensive reading of the Dolby metadata specs, and in reference to your question about the most accurate reproduction with the AC-3 Pro Encoder, I am prepared to make the following recommendations with notes:

If you're doing AC-3 Stereo, you can ignore everything I say about the Phase Shift option, it's greyed out of course.

Dialog Norm = -31 (this sets it at unity gain)
RF and Line Mode DRC = OFF (WYHIWYG)
DC High Pass Filter = ON (this operates at <=3Hz and takes DC bias out of the mix)
Bandwidth High Pass Filter = ON (this takes aliasing noise at >20kHz out of the encode, but it also lowered the final volume by -0.1dB in my tests)
90 Deg Phase Shift = ON (makes it easier for Pro Logic decoding on older equipment, Dolby says it is inaudible in 5.1 except in "very rare" cases)

Everything else can be left just as it is in the 5.1 DVD template; the only difference I can determine compared to the Studio encoder is the 90 Deg Phase Shift, but turning it off replicates the downmix pan bug I reported in the Audio forum. Interesting, huh?

peter-sieben wrote on 10/31/2018, 5:49 PM

Have been to the cinema today. The DCP playback went rather well, video and audio. The -6dB I did on the 24-bit AIF-files with Vegas before joining them with the videofile to a DCP-package resulted in an audio-volume that was not very different from other movies delivered to the cinema, I was told by the staff member. They had to twist the volume a bit up to get it to a decent loudness in the cinema theatre-room. Very odd BTW to see your own footage playing on a very big screen (room for 223 visitors), I was surprised to see the quality of my originally 1080x1440 anamorphic HD-footage (DVC-PRO HD, Panasonic HPX171 P2) being upscaled by a Barco 4K cinemabeamer.

I've asked them if they also could playback my 5.1 DVD, with the AC3 file I asked about above, but despite some efforts of the staff, they couldn't get the DVD-player hardware to work. Stereo-mixdown playback of my 5.1 DVD via a Sonos Playbase+dvd, on our hifi-stereo, on my computer and a 2nnd dvd-player with an 18 year old old tv via scart connected to it gave all a proper sound image, all tracks in their and well balanced. So I took my chance and delivered the DVD with 2.0 and 5.1 AC-files on it to the DVD duplication firm tonight.

Thank you also Christo. I use the same settings, although I keep the 90 Deg Phase Shift option off, my sound designer (working on tv-series and movies) adviced met that years ago. Reading your info suggests it's needed for older equipment with only Dolby Prologic as a decoder on it. I hardly see that equipment anymore at someone's home.