5.1 surround sound

[Pierre-luc Pare]

You’ll probably get 5 or 6 separate files (.wav/.aif, mono) that you will need to encode to a single AC-3 file with a Dolby encoder, or maybe Encore can do that. You have to use AC-3 because 6 PCM channel exceed the maximum bitrate allowed by DVD-Video specs. It will considerably reduce the file size, the bitrate for a AC-3 multichannel usually is 448kbps, so with your video not exceeding 7mbps, you’ll be ok.

[Roman Melekh]

* does 5.1 mean that you are supplied 6 DIFFERENT tracks of audio or are they all combined into ONE ac3-5.1 file?

6 wav files or 5.1 already encoded AC3.

* Will file size be a problem if burning to a standard 4.7 gig DVD?
No, all be OK. You must encode your video with maxbitrate 9800_minus_AC3’s_bitrate

[Riredale]

Surround-sound is my specialty. I shoot documentaries with a 4-channel audio setup mounted atop my camera. The front 2 channels are recorded onto the HDV tape; the rear 2 channels are fed into a Minidisc recorder.

After editing the video and getting the front audio right, I pull in the individual rear audio clips and sync them, then adjust levels. Once I am happy with video and audio, I encode the 4 audio tracks into a single ac-3 file (5.1 would follow the same process, but you’d have a center channel and an “LFE” channel, which in my view is totally bogus, unless you’re encoding for a 50′ screen in a large theater. To each his own…).

I use Vegas for all this, which makes it a very simple and clean process. Once I have the ac-3 file and an mpv video file (the MPEG-2 encoded elementary video stream) then I can take these into the authoring program and build my DVD.

Generally, stereo ac-3 runs at about 200Kb/sec; I run my 2/2 Dolby Digital audio at 320Kb/sec. A 5.1 file would probably need a bitrate around 400Kb/sec. You look at the total running time of your DVD, then use the following formula:

overall bitrate = 600 / minutes

so if you have a 90 minute video, your overal bitrate has to be 6.67Mb/sec in order to fit on a DVD-5 disk. Subtract from that your audio bitrate (say, .4Mb/sec) and you’re left with 6.27Mb/sec as your average video bitrate for your MPEG2 encoder. I would use min=0, avg=6.27, max=9.

Hope this helps.

[Roman Melekh]

/Generally, stereo ac-3 runs at about 200Kb/sec; I run my 2/2 Dolby Digital audio at 320Kb/sec. A 5.1 file would probably need a bitrate around 400Kb/sec/

No 🙂
Stetreo AC3 must be about 192..256, no more needed
2/2 – 320 – ok
5.1 file MUST be encoded at 384 or 488

Formula for calculation streams/speeds:

4.700.000 – total DVD5 size
i.e. menu ~200 megs
then – 4700000 – 200000 = 4500000 – total space for videos/audios/subs
4500000 / film_length / 60 * 8 * 0.96 = total_bitrate_for_film
If have 2 sounds – stereo (192) and 5.1 (448) then need:
total_bitrate_for_film – 192 – 448 = VIDEO BITRATE
max_bitrate_for_film is 9800 – 192 – 448
min_bitrate_for_film is VIDEO BITRATE / 2

only this formula is right!