Surround Sound AAC on a DVD

[advisionmatt]

I know this question has been asked before - but I've followed a few threads and it hasn't been spelt out how to do it!

I want to burn a 5.1 surround DVD. I've exported the audio as a six channel AAC and imported into into my Encore Timeline and can hear the sound. I've also set my project audio settings to Dolby Digital (is that correct?)

However - I'm finding that Encore wants to encode the timeline into a stereo file. I would assume there would be a box to say Don't Transcode - but there isn't. Just lot's of options how I want to re-encode the audio - which I don't want to do!

[Stan Jones]

If the file is not DVD 5.1 legal, Encore will transcode into Stereo.

You want an a3c file, not AAC.

Encore only does 5.1 passthrough, and you can't preview the 5.1 in Encore.

[advisionmatt]

Sorry - I meant AC3! I don't mind not previewing it - i'm just hoping it will pass through.

I'll encode again and see what happens. it's just worrying having boxes saying the audio will be stereo, and seeing the audio being Transcoded, when there doesnt seem to be any options to tell it not to!

[Stan Jones]

That suggests it may not be DVD legal.

Richard Knight may drop in; what are your export settings for this?

His comment from an old thread indicates that "For a dvd the max Dolby Digital rate is 448.... If you use the wrong rate Encore will re-encode the audio."

[advisionmatt]

I think you've hit the nail on the head! I've re-exported the Ac3 audio at 448 and straightaway it's put Don't Transcode in the audio settings which is what I'm after! I'll burn the DVD and see if it passes through ok!

Thanks for you help!! Fingers crossed!....

[Stan Jones]

Let us know!

[advisionmatt]

It has burned the disk ok - so I will take it home tonight and play it on my surround sound to see if it has worked correctly! It is a little annoying however that it hasn't filled the disk up! I've put it on Automatic Transcoding of the video as I thought that would maximize things. Its a long show - about 2 hours, so I want to get the best quality. Encore has reported it as 4.6 GB with about 100k free - but upon making the DVD up it only seems to be just over 4GB free with a massive 700Mb of free space! Any way of filling it up more?

[Stan Jones]

A 4.7 GB disk is actually only 4.37 GiB, so it depends on which type of info you are using to read the size.

It gets complicated because the Premiere Pro export estimate (last I checked) and parts of Encore are reporting Gibibytes (GiB), not Gigabytes (GB).

How are you reading the 700Mb free?

[advisionmatt]

The contents of the Video_TS folder was only 4GB and when I dragged it into Nero it said there was 700mb free. Upon burning the dvd you could clearly see that there was potentially more space.

[Stan Jones]

By any chance, did you transcode the video before you changed the audio? Encore uses the status of the disk when you select "transcode now" to determine how much room is left.

[neil wilkes]

That's not really 700Mb you know.

On discs, the Mb and Gb are done in multiples of 1,000 and not the 1024 we use on computers.......it adds up.

How did the disc go, and what did you use to make the AC3 file?

Also do you have access to a DTS encoder? That is far less lossy than AC3 and without the metadata problems an AC3 file can give you too messing up all your levels.

Just curious really

[advisionmatt]

In the end I took off the Automatic transcoding, and kept changing the VBR 2 pass bitrate until I got the minimum about of free space before it said I exceeded the capacity. I got it down to saying I had about 12Mb left!

However, after building the DVD it still was only 4.3Gb and my DVD burner said there was about 400 Mb of free space! Very frustrating as it could have got my 3.9Mbps up to about 4.3 which would have been more satisfying!

i rendered the files in Grads Valley Edius which I use to edit. The files were mixed in Audition and exported as 6 .WAV, and in Edius I exported the video with 6 channel audio as an Dolby Digital AC3 at 448!

would you recommend DTS - and if so what’s the best software/plug in for me to export it?

Im also a bit lazy about doing two mixes - so am kinda relying on the DVD player to do the down mix for the large majority just watching in Stereo. Do you know what kind of algorithm it uses?

[neil wilkes]

Hiya.

Again, I would be very careful about going too close to the wire when encoding video files.

1. The discs are reported as different sizes when compared to computer HDD. Whilst it may say 4.7Gb on the packaging it is not that much in reality so be careful.

2. The closer you get to the outer edges of the disc, the riskier the burn becomes - the vegetable dye used can be thinner at the edges so I would never try to cram a written disc too full. A replica, yes but not written.

Personally I think DTS blows AC3 away in terms of the image and the quality. Here's why:

AC3 at 448Kbps is not full bandwidth/full range - that requires 640kbps which is out of spec for DVD-Video. You will get a situation where all the top end goes unidirectional above somewhere around 14-15kHz and that is where all the air & space is on a mix. Yuk.

Plus you also have to factor in downmixes to stereo as well as RF output and all that means is compromise, compromise compromise. Watch the metadata too - setting production information will attenuate the mix and setting Dialnorm will attenuate the L-R-Ls-Rs channels respective to the C channel, which in these cases is always assumed to be carrying just dialogue and this brings me to the core of my issue with AC3.....it was developed for film use, not music use and the metadata will work with compressors & limiters to ensure dialogue intelligibility (ie turn the other channels down given the DRC profile conditions). Sadly turning this all off does not help either, as a player where DRC has not been turned off (it is usually ON by default in DVD/Blu-ray players) when it gets to play a file that has no DRC flag set will assume it should be "film main" and bring the hammer down accordingly. The usual approach is to set to "Music Light" as this is the least intrusive - and if the DRC setting is OFF in the player this flag will have no effect.

DTS on the other hand uses a bitrate of 1536kbps (the same as 16-bit 48kHz PCM audio) and in usual use does not allow setting of dialnorm (if this must be set, set it to -31 or no attenuation) and it is full bandwidth. Yes it does use 3 times the space on the final disc, but even if you are running PCM stereo & DTS that still leaves a good 6Mbps for the video, and that should be plenty. Surround fans will thank you for it.

There is a downside - DTS is an optional codec, not a mandatory one so cannot be used as the sole stream. The end user must have either a DTS decoder in his/her player or their amplifier and I assure you all surround fans have this. If you have room, add an AC3 as an afterthought but nobody will play it.