Why a 2.0 track on DVD's? (1 Viewer)

[Eric-S]

Why do discs use space for a 2.0 track? Don't DVD players have the ability to downmix a 2.0 track from the 5.1 mix? Just something I have always wondered.


Thanks,

Eric

 

[ChristopherDAC]

Sometimes the 2.0 soundtrack is a different mix, such as in a case where a movie had separate stereo and surround mixes, or where the 2.0 is an original matrix-surround mix and the 5.1 is a remix. In other cases, the DVD producer may simply feel that the downmix mode isn't good enough, for one reason or another.

 

[MarkHastings]

Probably because 2.0 doesn't require downconversion which delivers a better result...

Also, being only 2 channels, I'm sure there's more than enough room on the DVD to include it.

 

[Mark Kalzer]

Usually it's because the 5.1 is a radically different mix from the original in the case of old movies or television shows.

As for more recent ones, it's typically a case of this belief that 2.0 tracks playback better on stereo/pro logic systems then 5.1, or that 5.1 tracks have to be compromised in some way so that they can play back effectively on stereo/pro logic systems. In the latter case, having a 2.0 track supposedly helps the quality of the 5.1 track.

Personally, I don't think anyone at this point who doesn't have a 5.1 system really cares about what minor difference down conversion would make, but thats's just me.

 

[MarkHastings]

Also, doesn't the DVD require at least one dolby track? In the case of some DTS discs, since there usually isn't a ton of room to include a DD5.1 track, they include the smaller DD2.0 track to meet the requirements.

 

[Jesse Skeen]

What I've always wondered is why are so many mono titles in 2-channel "big fat mono", instead of 1-channel Dolby? Mono sound is supposed to be played through just the center channel, and if for whatever reason you really want to play it through the left and right instead you can set your reciever to do that.

Another gripe I've had for a while is that they should use PCM a lot more often than they are- It doesn't take up that much more space, especially on titles that just have one audio track to begin with!

 

[ChrisWiggles]

Um, it takes up a *LOT* more space than DD does. Depending on the DD bitrate, many times more, like 10 times as much space.

PCM is a terrible choice, unfortuantely that's what Sony is doing on some Blu-ray releases.

 

[Esten]

Yeah, PCM would take up like 1.5GB for a 90-minute movie, or about that. A DD would only take up 200mb, if that.

 

[Nick Martin]

I began enjoying 5.1 surround late last year, so for many years the one thing I noticed when comparing a 2.0 track and a downmixed 5.1 track, is that the downmix is lower in volume, and can sound a lot like you have the dynamic range compression set to 'high'.

A DVD like "Independence Day" is a great example. Its 2.0 track has a range in volume similar to listening to the discrete 5.1 track.

 

[MarkHastings]

Ugh! Tell me about it! When watching 5.1 HD content through my TV speakers, the sound is awful.

 

[ChristopherDAC]

I disagree with this statement. PCM provides the highest audio quality, and depending on the situation, its bitspace needs can be quite modest. In the case of Sony Blu-ray releases, a 5-channel 16-48 track takes up a little less than 4 Mbps out of an available 36. Stereo PCM on DVD requires 1.5 Mbps out of a possible 9. Considering that video compresses far more easily than audio, the tradeoff doesn't seem too bad to me.

 

[ChrisWiggles]

PCM is not compressed and extremely wasteful. And if you want to run high-resolution PCM, it's even more astronomically wasteful. In an age where lossless compression is readily available for the most demanding tasks, there is really little reason to use uncompressed anything, whether that be audio OR video. You may cling to PCM, but it's an irrational desire, and one that is extremely detrimental when completely adequate alternatives exist that conserve bandwidth and data space.

We can agree to disagree, but really I don't think there's anyone out there who is going to say that PCM is better than using lossless compression, and in most cases lossy compression will serve marvelously.

There are very good reasons why PCM is not really ever used on DVDs, and it's because it just EATS up data space and available bandwidth. If you were to try to do 5.1 in PCM, say goodbye to any hope for even VHS-quality images!

 

[MarkHastings]

He did say "depending on the situation" - If you were to make a 10 minute DVD, video quality wouldn't be affected no matter what you did to the audio (i.e. compressed, uncompressed, lossless compressed, etc.)

 

[Chuck Pennington]

PCM might seem wasteful to you, but Dolby Digital is not a good alternative - at least not in the configuration found on DVDs. I made hybrid DVDs of the original sound mixes to GREASE, SUSPIRIA, and several other films and kept the sound in PCM Stereo. I did an experiment encoding it into Dolby Digital - at 448 kbps. The sound was lower in volume and lost detail and overall strength.

I look forward to PCM or some kind of lossless audio on one of the hi-def disc formats, but for the time being...

 

[ChristopherDAC]

Well, 5.1 PCM isn't even a possibility on DVD. The spec' doesn't allow DVD-V to have it. What else doesn't the DVD-V spec' provide for? Lossless compression! I created a home-brew DVD not long ago which played a little under an hour, with 16-48 PCM stereo, on a DVD-5, and the results were more than decent (about as good as they could have been, considering the composite source and the hardware I was using). The video bitrate was bumped up pretty high, but even still there was plenty of space left on the disc (i.e., bandwidth-limited condition).

As I mentioned, on Blu-Ray, the bandwidth requirements for multichannel PCM aren't that severe. Just as importantly, we've already had posts in the HD Software and Hardware areas calling for discs with both Dolby TrueHD and dts-MA lossless audio. Rather than waste space on two utterly redundant audio tracks, and money on licensing two interchangable CODECs, PCM is the better option.

 

[BrettGallman]

Sony's bigger mistake is not using VC-1 compression. If they would, there'd be pleny of space for the PCM tracks on their BD releases.

For DVD, however, it's just not feasible in many cases for PCM tracks. I don't think it's even possible to do 5.1 PCM on DVD. However, if the film's original soundtrack is only mono or stereo, PCM is the way to go.

 

[ChrisWiggles]

The demand for redundant lossless tracks is pure ignorance, I certainly agree. But using PCM is an even worse choice. You'll end up with roughly the same data space doing that than you would doing redundant lossless codecs, but you suffer the additional loss of having infringed on the available bitrate, which is not a minor issue.

Going to PCM is just a huge step backwards and is really just unbelievably irrational from an engineering standpoint. Maybe from a business standpoint in avoiding royalties for superior delivery, such as VC-1 or h.264 or DD/DTS codecs, but as far as actual delivery quality, it's an indefensible move.

 

[MarkHastings]

Why do you keep interjecting impossible aspects to support your anti-ucompressed audio point?? Optical media throughput doesn't allow for uncompressed video, but it DOES allow for uncompressed audio, so there's no need to even mention uncompressed video in this discussion.

And by the way, if the throughput allowed uncompressed video then I'd sure as hell be opting for that as well (as would probably most others).

 

[ChrisWiggles]

I think your characterization here of what people would want is quite off the mark. The potential for uncompressed video isn't even hardly realistic in the professional world, as it's incredibly wasteful. I think the demand for "uncompressed" is really an irrational one that a lot of laypeople hold because they think it must be better. Well, for all the problems that compression (especially too much compression or poorly done compression) can cause, have you imagined what fully uncompressed video would look like using the same data space and bandwidth? You'd be looking at a postage-stamp sized image, and sure all the handful of pixels you'd be looking at would look great, but the overall image would be ridiculously useless because the resolution would be so low.

This whole "I want uncompressed because uncompressed is better" is really just ignorance on the matter.

 

[BrettGallman]

I'm just speaking for the Sony releases on BD so far. At this point, the Samsung player can't decode the new DD and DTS lossless codecs; however, it can do PCM. So, I think it makes sense to use PCM and VC-1 at the moment because that does provide the best quality. But in the future, it certainly makes sense to just have one compressed soundtrack because the quality will be the same as PCM but won't take up as much space. But for now, PCM on BD is the way to go (along with VC-1, of course).