DVD audio for film sounds like mp3's? WTF????

[PlugHead]

OK,

I've been listening (on headphones) to the audio quality of a few DVD films (I could mention titles, but it's irrelevant, AFAIK). I constantly hear compression artifacts similar, or identical to the hash associated with mp3 encoded audio.

Now I know DVD picture and audio are compressed, and require it to get past the bottlenecks of multi-channel with picture, but I was under the impression that fidelity isn't compromised. I assume this is a lie, and the audio seems to be nothing more than mp3 quality. This low quality makes for a distracting listen to these otherwise fantastic movies; WTF? Production costs of making films, hi-res. 96k audio - for what? To sound like your kid's iPod playlist?

Maybe I've just had a couple of bad DVD's, but 3 out of 3 sounded pretty poor through headphones. BTW - compression artifacts are WAY less noticeable thru speakers - you have to listen quite intently to notice it...

Any one else hear this, or have insights? Or is it just me?

[dasbin]

5.1 DVD movies use lossy audio compression, so I'm not sure why this is a surprise.

Some are better than others. The production house can choose the bitrate and format.
Most people seem to prefer DTS over AC-3.
If it's very badly noticeable, though, something else might be going on. I've only noticed it briefly in a couple lower-bitrate scenes with rock music (cymbals are always the worst, it seems). Normal dialogue and SFX seem to do pretty well with compression.

[PlugHead]

Originally Posted by dasbin

5.1 DVD movies use lossy audio compression, so I'm not sure why this is a surprise.

Some are better than others. The production house can choose the bitrate and format.
Most people seem to prefer DTS over AC-3.
If it's very badly noticeable, though, something else might be going on. I've only noticed it briefly in a couple lower-bitrate scenes with rock music (cymbals are always the worst, it seems). Normal dialogue and SFX seem to do pretty well with compression.

FWIW,

I'm listening in stereo (with cans) - maybe they use the same codec as with 5.1, I don't know...

In any case, I know the top end sounds mangled, and less than vibrant - more like an mp3 @ 96kbs (give or take a few loose bits)

Shame - I thought audio might actually sound better than CD, but sadly that's not the case here...

[ctms777]

When authoring DVD's I choose Dolby AC-3 compressed audio for stereo and surround because Audio & Video are fighting for space on the disc. The video guys say the same about mpeg2video.
But to the general public who listen and watch on Chinese Surround-sets costing less then 100 Euros including speakers, DVD-player etc, it really really really doesn't matter.Really.Not.
And to the Hifi-freak with his 100 Euro powercables, it really doesn't matter that much either. To say that 224kbs Dolby Digital AC-3 (for stereo) or 448kbs (for surround) sounds bad is just not true. It doesn't sound that bad at all. If you want better quality buy a CD. With good converters that doesn't sound bad either, in spite of fashionable comments.

[DrDeltaM]

Lotsa DVD's sound bad yes. It's however a combination of the datacompression and the audiocompression imo: DVD audio pumps a lot, I find that often very annoying. Like somebody lightning a cigarette in the movie pushing down the ambient rainsound.
I don't have a surround system, so i've been wondering if it could be cuz of some software algorithm that collapes 5.1 to 2.0. It seems tho that DVD's in general contain a seperately stereo audio track...

This stereo audio track can actually be an mp3, tho the quality of it can be set by the DVD encoder.
See here an overview of the possibilities of audio on DVD Video:
http://www.robertsdvd.com/video-audio.html

The only rule is the 6144kbps bandwidth limit.

So it really depends on how many audiotracks of what kind there are on the DVD. Several languages in audio (not just subtitles) eat up that bandwidth fast. And even if there are just a few audiotracks, they still might not use all bandwidth available.
Also, the better the surround audiotracks are, the fewer space there is left for the stereo.

[dbbubba]

You guys are right in your assumption that DVD audio has a HUGE amount of data compression applied to make the audio fit on the DVD in the first place.
I don't know the specs, but it's pretty much an .mp3 type data stream.

I have a few books on audio for film and TV and they pretty much stress how historically audio has been thought of as a "special effect" in film. It definitely is considered as "support" to the picture, so it will always get less consideration.

Truthfully, in film production the only "hi-fi" portion of the audio is the music score which was recorded in a pro studio or soundstage.
The dialog is almost 99% mono, up the center and if you've ever been on a film set you'll quickly see that the sound recordist and his boom man are about as important as the union truck drivers! They'll almost never do another take for sound reasons and besides, they can always do ADR. It's almost like the thought is that it's great if the sound recordist gets the dialog during the take, but all audio can be re-done, so it doesn't really matter.

The SFX and ambience are added in post and since everything has to happen really quickly they don't have the luxury of taking their time. Also, since picture has precidence any editorial changes mean that the audio mix people have to quickly adapt to the new edited verson. All this adds to a "hurry up.. yeah, that's good enough" attitude.

The whole mind set in film production is that since audio supports the picture it is inherently secondary. This is why if you listen to the soundtrack without picture the edits seem sudden and jarring. They have developed techniques that are totally different than music editing. A large part of film editing wouldn't "work" without the picture to "explain" the edits.

So... don't expect too much!

As an interesting note:

I used to install and service EXTREMELY high dollar home theatres for millionaire types who had nothing but money to spend. I was always amused that they'd spend thousands of dollars on audio gear only to playback crappy DVD audio!

Ever look at the pixelation on DVDs?
The picture is just as data compressed and lossy!

Ahhhhh.. It's just a remake of a TV show from the '60s or a remake of another movie anyways! Most music is "consumed" by people wearing iPod headphones, so why shouldn't the DVDs and video suck, too!

Danny Brown

[PlugHead]

Originally Posted by dbbubba

You guys are right in your assumption that DVD audio has a HUGE amount of data compression applied to make the audio fit on the DVD in the first place.
I don't know the specs, but it's pretty much an .mp3 type data stream.

I have a few books on audio for film and TV and they pretty much stress how historically audio has been thought of as a "special effect" in film. It definitely is considered as "support" to the picture, so it will always get less consideration.

Truthfully, in film production the only "hi-fi" portion of the audio is the music score which was recorded in a pro studio or soundstage.
The dialog is almost 99% mono, up the center and if you've ever been on a film set you'll quickly see that the sound recordist and his boom man are about as important as the union truck drivers! They'll almost never do another take for sound reasons and besides, they can always do ADR. It's almost like the thought is that it's great if the sound recordist gets the dialog during the take, but all audio can be re-done, so it doesn't really matter.

The SFX and ambience are added in post and since everything has to happen really quickly they don't have the luxury of taking their time. Also, since picture has precidence any editorial changes mean that the audio mix people have to quickly adapt to the new edited verson. All this adds to a "hurry up.. yeah, that's good enough" attitude.

The whole mind set in film production is that since audio supports the picture it is inherently secondary. This is why if you listen to the soundtrack without picture the edits seem sudden and jarring. They have developed techniques that are totally different than music editing. A large part of film editing wouldn't "work" without the picture to "explain" the edits.

So... don't expect too much!

As an interesting note:

I used to install and service EXTREMELY high dollar home theatres for millionaire types who had nothing but money to spend. I was always amused that they'd spend thousands of dollars on audio gear only to playback crappy DVD audio!

Ever look at the pixelation on DVDs?
The picture is just as data compressed and lossy!

Ahhhhh.. It's just a remake of a TV show from the '60s or a remake of another movie anyways! Most music is "consumed" by people wearing iPod headphones, so why shouldn't the DVDs and video suck, too!

Danny Brown

Yeah, I know - I've done more than a couple of location sound gigs - what a job. Low ranking is the word, tho sometimes the food is great, but more often than not it's a bear of a job, and the bread is getting worse (at least this side of the fence)

As for DVD sound quality issues: I thought it was supposed to be a step up in terms of fidelity, not only for picture. I don't think it's setting the bar too high in expecting better audio than our current 44.1/16 as the 'standard' for CD. Why is it with a format more than 10X the capacity, we can only get at best bit rate, 448 kbs, and more often, way way less (for audio anyways...)

Shame again - let's hope blu-ray takes the edge in audio delivery...

regards,

[dbbubba]

I've been a professioinal audio guy since 1975 in one way or another.

For a few years I had the opportunity to work in film as a camera crane operator because my good friend and I obtained a truck mounted 26' location crane. Because I know AC real well, I did gennies (easiest work on the set!) and Best Boy Electrical as well.

I never wanted to do sound!

A highlight of films that I worked on were Firestarter, Maximum Overdrive and a few other Stephen King films done at Dino De Laurentis' complex in Wilmington, NC.

It was fun!

We blew stuff up, crashed cars, trucks, airplanes, houses, etc...
Fire, explosions!
I watched the director take a little girl named Drew Barrymore out in the woods and make her cry before a few scenes.
I got to hang out every morning for a few weeks with Stephen King while we drove to location.... one strange cat!
He liked to ride with me in the camera crane for some reason.
I guess I'm cool!

Good money, too!

I financed my 24 track room this way in 1986!
I bought that studio and never did another film!

DB

[ctms777]

The pumping you can hear on DVD's is caused by the AC3-metadata. When encoding AC3 you can tell the home-user-decoder how to compress the signal. The default setting in any Dolby Digital AC3 encoder is to use it. You can ofcourse also turn it off.
The AC3 spec is also been thought out for digital television, and the compressor in the decoder (yes, it's in the decoder) is to keep the level differinces between movies, talkshows, commercials etc. under control.
That's why they also included the "dialog normalisation" parameter. If you search on the Dolby website you can find a pretty good indepth explanation of that parameter. I'll try give a short version here:
The "dialog normalisation" parameter can be set from -31db to -1dB. If you set it at -31 your audiolevels will be untouched. When you set it at the (default) -27 setting your audio will be attenuated by 4dB by the decoder (remember it's metadata). When it's set at -20 the attenuation is 11dB, etc..
The goal of this parameter is to level out the volumedifferences between commercials that could have the dialoglevel at an average of -6dB (I'm just making up numbers here) and movies where the dialoglevel could be at an average of -27db. And when somebody whispers in that movie, that's where the autogaincircuitry kicks in.
That may be very nice for digitalTV broadcasts, but totally inapropiate for DVD, where one would like to control that with their own expensive audiogear(-slutz).
I agree that DTS sounds better better then AC3, but it also uses a lot more bandwith, and for me that is often not an option when trying get 3 hours of video, stereo and 5.1 audio on a DVD. The video people who make DVD's probably don't know (or care) how to set the AC3 encoder, that's why AC3 mostly sounds worse then it could.
There are however DVD's that sound amazing, like the Led Zeppelin one or the Norah Jones one, Dixie Chicks one. But they use uncompressed for the stereo versions.
By the way, when you see a lot of pixelation on a DVD then that's due to a low bitrate for the video. But unlike the Dolby AC3-encoder, not all MPEG2 video encoders are created equally, and prices range up too $50.000 and beyond, while I think Sony has one that only they can use for their own DVD's. Ofcourse lower bitrates still look decent on these encoders.

Coen Thomas

[pounce]

in my time on shoots, i've decided that directors don't know shit about audio or actors. they seem to know a little about getting shots, and are disproportionately concerned about lighting. they ought to be called the cinematography directors cause the sound folks have to fight em half the time. i can't believe this hasn't been better addressed in film schools, or if it is only noticed by folks like boom operators and other audio guys. i watched a bit of a series on sundance channel or ifc and it was about film students. same thing, their inability to -direct- actors was amazing. while i appreciate that a good director has to be a good storyteller, and that film/video direction requires knowledge of a number of disciplines, their lack of knowledge or respect for audio is alarming at best.

[Jonny Mumra]

Hi dude.

Yes i hear it and its a dissapointment to me too.

I often watch movies and listen to the sound through event 8 actives
its quite noticable and annoying.