The 5.1 Element: DVD lets the sound surround you

A single-sided DVD disc, know as a dvd5 in the tech world, holds 4.7 gigabytes of information. A dvd9 (single-sided, dual layer disc) holds 8.5 gigabytes, a dvd10 (double-sided, single layer disc) holds 9.4 gigabytes, and a dvd18 (double-sided, dual layered...
October 1, 2000

A single-sided DVD disc, know as a dvd5 in the tech world, holds 4.7 gigabytes of information. A dvd9 (single-sided, dual layer disc) holds 8.5 gigabytes, a dvd10 (double-sided, single layer disc) holds 9.4 gigabytes, and a dvd18 (double-sided, dual layered disc) 17.5 gigabytes. In terms normal people can understand, this means producers can stop mourning the fact that no one will see all the great footage that ended up on the editing room floor.

The arrival of DVD has significantly widened the canvas filmmakers work with. Able to support multiple story lines, widescreen movies, nine different camera angles, interactive features and up to 32 subtitle or karaoke tracks – among other features – DVD allows filmmakers to get funky. What DVD has done for picture, it has also done for sound.

Since the 1992 release of Batman Returns, most feature films have used 5.1 sound technology. With three channels in the front, two surround sound channels and a low frequency bass channel delivering discreet sound, viewers feel as if they’re in the middle of the action. Before DVD, this experience was limited to the theater. ‘A standard VHS machine is not capable of playing back [5.1] because there isn’t enough space on the tape to record all that information,’ says Richard Spence Thomas, chief engineer of Spence Thomas Audio Post in Toronto, Canada. ‘Along comes DVD, and bang! All of a sudden we can do it.’

Everything old is new again

For older titles enjoying renewed interest in the market, the improved technical quality offered by DVD means re-formatting soundtracks to meet today’s standards can be time consuming and costly. ‘The cost of upgrading audio for DVDs was higher than we anticipated,’ says Jim Kelleher, director of international video and DVD for National Geographic Television in Washington, D.C. Kelleher cautions that the cost of enhancing audio can vary greatly depending on what country the work is done in, but estimates that re-mastering a one-hour program in the U.S. can run between US$7,000 and $10,000. If elements are missing (with which to create a 5.1 environment), the cost can reach $20,000.

Producers creating DVDs for titles executed in standard stereo have three options. The first is not to bother creating a 5.1 version and simply transfer the film’s existing audio mix to DVD as is. Says Thomas, ‘The first quality difference [of DVD] is that the delivery medium itself is digital. Because DVD records and plays back digital information, there will be no signal degradation created by the DVD itself, no matter what information you put on it.’ Tracks can be ‘cleaned-up’ in post before being encoded on the DVD, so they sound crisper. This is the least expensive option and requires little effort, as it’s part of the DVD authoring process.

The second option available to producers involves taking a film’s original stereo mix and using it as the basis for creating a 5.1 environment. To do this, Thomas explains, the existing stereo mix is put in the front channels, which is essentially where it was to begin with. To elevate the sound to 5.1, new material is added to the rear and bass channels.

‘Most people just assume 5.1 can be created from mono or stereo sound. It can be, but it’s a laborious process and it’s a very refined art,’ cautions Doug Mountain, senior DVD author and new media evangelist for Spruce Technologies, San Jose. Mountain recommends cutting two versions of the stereo mix – one for the front channels and another for the back ones. ‘That way, the levels can be mixed and set appropriately,’ he says. ‘When you put them together, you get an amazing, full experience.’

Thomas warns against distorting the ‘phantom center image’ when using stereo effects from sound libraries to flush out the much larger 5.1 environment. In stereo, a ‘phantom image’ is created when sound from the front left and right speakers appears to originate from the center. In 5.1 there’s a dedicated center speaker, so the left and right speakers may be moved farther apart. Distortion occurs when the stereo sounds used to create the 5.1 environment are not robust enough to fill the space. As a result, the sound doesn’t correspond to the images on the screen. Says Thomas, ‘This happens because we’re trying to squeeze old sounds into new technology.’

According to Mountain, the process of promoting stereo to 5.1 can be completed within days and costs between US$5,000 and $15,000.

The final option producers might consider involves gathering all the original sound elements from the film and mixing them anew in 5.1. Both Thomas and Mountain agree that this is the most time consuming and costly approach. ‘This is the hardest to do because most of the original elements have either deteriorated or been lost,’ explains Mountain. ‘Finding the original elements and remixing them can run hundreds of thousands of dollars.’

‘If you go back to scratch, you can actually do a much better job because you’re not limited,’ says Thomas. ‘[But,] we have higher standards today. We have a delivery system that doesn’t hide imperfections. You can hear a lot more on DVD than on VHS.’

Do you hear what I hear?

Mountain urges producers recording sound for a current film to gather as much ambience for the sound editors as possible: ‘There’s more space to fill than there used to be because we now have five discreet full-range channels and one sub-channel. The more ambient recording picked up and added into the surrounds, the better the final product. It fills out the surround experience.’

Thomas estimates a sound editor’s rate is around US$3,000 to $4,000 a week in the studio. For producers who can’t afford to take sound editors and a five channel recording rig on location – a venture truly beyond the scope of a one-man operation – portable multi-channel recorders are available. As these are often hard disk-based, however, Thomas hesitates to endorse their use. ‘I believe if you’re on location, you want a nice, robust recording medium – one that’s proven and not likely to fail. Hard disks are very sensitive devices. If I were going out to shoot today, I would take an analog tape machine. They’ve been in use for 35 years, they sound fantastic and they work every time.’ Ambient noise should be captured separately to the dialog or main soundtrack. In general, the arrival of 5.1 has affected very little change to the methods of location shooting. ‘The 5.1 element happens back in the studio,’ says Thomas.

As 5.1 can be folded down to stereo, music soundtracks should be mixed in 5.1. ‘Assuming you’re having original music written and played for you, ask that it be mixed in 5.1 so your music elements are in true Dolby Digital surround,’ advises Thomas. ‘It costs a little more, but it’s not outrageous amounts of money.’

Not everyone listens to DVD on state of the art surround sound systems. Although DVD players have a downmix decoder that automatically decodes 5.1 to fit a stereo or mono output system, DVDs are sometimes encoded with two soundtracks: one in stereo and one in 5.1. ‘Some people don’t like the way the decoder downmixes,’ explains Jim Taylor, author of DVD Dymystified and creator of the internet DVD FAQ. ‘In my opinion, that’s a lot of extra work, because the person probably doesn’t have a good enough system to hear the difference.’ Taylor does advise sound editors not to put all bass sounds in the low frequency channel: ‘This channel was designed to add an extra bass kick for things such as on-screen explosions. If all the bass is kept here, it can be lost in the downmix.’

Taking matters into your own hands

For around US$60,000, producers can do the post work themselves. ‘There are many new digital consoles that have come on the market in the last few years that have 5.1 panning built into them,’ explains Mountain. ‘Some of these are even available in music stores and they literally allow 5.1 mixing environments to be set up in an office. If a producer can operate a work station to edit film, they can operate a work station to edit a soundtrack.’

Whether producers opt to handle sound internally or externally, Mountain urges them to move with the times: ‘Plan on doing 5.1 sound from the beginning. Producing in stereo only is so short sighted these days. Producing in stereo and deciding to revisit it in 5.1 later is also a sad mistake. Coming back to revisit things gets twice as expensive. If you do it in 5.1 from the beginning, you can fold it into stereo later. Ultimately, if you plan on serving the home video market, 5.1 is the medium of choice – for now and in the coming future.’

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