Experiments in DIY Dolby Headphone

I know that Silverline is supposedly going to start including Dolby Headphone on their DVD-As, but what about all of our old surround recordings?

It would be nice to be able to play any surround recording in a portable player like an iPod, and hear something approximates the surround that we hear at home. Well, at least in theory.

So I thought I'd experiment a bit.

I have an old license for Power DVD 4.0 (this is an old version), and they have a Dolby Headphone plugin, which I bought a while back but never used very much. I played some DD5.1 surround music through it with the DH plugin, and then captured the native 16/48 audio en route to the soundcard using total recorder.

The captured audio pretty much matches what I was hearing when listening directly, and does provide a semblance of listening to the original recordings in a home-theater surround speaker configuration. There's at least one issue, though. Power DVD 4 isn't mixing the LFE channel into the sound output (regardless of whether I use DH or not). To make it worse, I'm getting a little distortion when the LFE is supposed to be used.

Here are some audio clips, converted to high-bitrate MP3. The first is a channel check, the next two are from the FLips Yoshimi DVD-A.

channels

yoshimi

realize

I'd suggest right-clicking these and saving them. They stutter when I play them directly in Firefox (maybe this is an issue with 48khz versus 44.1...a lousy player in the browser?).

Let me know what you think. I wonder if newer software would fix the LFE issue, or use a more sophisticated algorithm.

I am pretty clueless about the Dolby headphone thing. What exactly was it developed to do?

JonUrban said:

I am pretty clueless about the Dolby headphone thing. What exactly was it developed to do?

Click to expand...

Uses 'psychoacoustic' signal processing algorithms to turn a 5.1 signal into a stereo one, that, when listened to via headphones, sounds like surround.

http://www.dolby.com/consumer/technology/headphone.html

The theory goes like this:

Since y'all only have two ears, (I have five and a big ol' bass ear) and since we can hear perfectly good surround with just two of them, then it is possible to replicate surround with just two channels, as long as the two channels are kept separate, as with headphones. There were experiments done in the eighties where a dummy head with ears with microphones was placed in a room with a discrete quad setup. The two channels captured with the microphones could then be listened to with headphones and because it contained all of the inflectional information that a real head with real ears would pick up, It sounded like you were sitting in the room with the quad system and you would be in the surround sound. The Dolby Headphone project went beyond this idea, with the idea that the inflections and delays could be electronically encoded to eliminate the room and the dummy head. I will leave you to judge how well it works, but theoretically, you can listen to a dolby headphone track through headphones from any stereo machine and you will get an illusion of surround. There have been a few DVD Audio discs released with a Dolby headphone track, but I don't recall which ones they are. It won't work through speakers, because the mixing of the audio through the air spoils the effect.

The Quadfather

Beer Monkey said:

Uses 'psychoacoustic' signal processing algorithms to turn a 5.1 signal into a stereo one, that, when listened to via headphones, sounds like surround.

http://www.dolby.com/consumer/technology/headphone.html

Click to expand...

Yeah, what the Quadfather said.

I'd love to hear opinions as to how you guys think my samples sound, through headphones.

I heard a number of Dolby Headphone demo's at CES sometime in the late 90's. Sennheiser and a few other makers had them, they were all the rage. The demos were impressive, but . . . there's not a whole lot about demos that's all that different from model homes with their 3/4-size furniture. All were movie samples -- no music -- cherry-picked to show off all the strengths but none of the weaknesses. (I'll never forget the 1987 Matsushita demo tape for S-VHS, with lots of white flowers.)

In 1978 I bought a set of quad headphones from Pacific Stereo from a salesman trying hard not to laugh. This was the kind with two drivers in each cup, like something you'd see in a Saturday Night Live commercial parody. They didn't work, and neither did the $500+ Sony "5.1" headphones I tried just a few years ago.

The history of surround sound through headphones for three decades closely parallels that of other great technologies like shark cartilage and free-energy wheels.

Beer Monkey said:

I know that Silverline is supposedly going to start including Dolby Headphone on their DVD-As, but what about all of our old surround recordings?

It would be nice to be able to play any surround recording in a portable player like an iPod, and hear something approximates the surround that we hear at home. Well, at least in theory.

So I thought I'd experiment a bit.

I have an old license for Power DVD 4.0 (this is an old version), and they have a Dolby Headphone plugin, which I bought a while back but never used very much. I played some DD5.1 surround music through it with the DH plugin, and then captured the native 16/48 audio en route to the soundcard using total recorder.

The captured audio pretty much matches what I was hearing when listening directly, and does provide a semblance of listening to the original recordings in a home-theater surround speaker configuration. There's at least one issue, though. Power DVD 4 isn't mixing the LFE channel into the sound output (regardless of whether I use DH or not). To make it worse, I'm getting a little distortion when the LFE is supposed to be used.

Here are some audio clips, converted to high-bitrate MP3. The first is a channel check, the next two are from the FLips Yoshimi DVD-A.

channels

yoshimi

realize

I'd suggest right-clicking these and saving them. They stutter when I play them directly in Firefox (maybe this is an issue with 48khz versus 44.1...a lousy player in the browser?).

Let me know what you think. I wonder if newer software would fix the LFE issue, or use a more sophisticated algorithm.

Click to expand...

I listened to the above clips, and the channel check impressed me at first. However, after that, it just sounded like a regular stereo recording with some reverb effects.

Still, a cool idea though...

The ears/brain can tell the location of sounds by at least two mechanisms.

One of them is the way the pinna (outer ear) changes the tonality of an incoming sound depending on the angle of incidence. This has been studied at length and the resulting process is known as the "head transform functions". Systems like Dolby or SRS use this algorithm to change rear channel information as if it has gone around the pinna. This works up to a point.

The second mechanism is that the head is never stationary -- it "fidgets", even if imperceptibly. But these tiny movements and the phase changes they induce give clues to the brain as to whether the sound is coming from a point in front of, above, behind, etc. of the head. No current headphone system compensates for this effect.

Maybe in the future there will be systems with accelerometers in the headphone. Until then the "surround headphone" schemes are lame.

I've been doing a lot of headphone listening lately. It's not that easy - speakers are definitely preferred.

Dolby Headphone certainly captured my attention so I went to the Dolby site where they have demostration tracks one can play over net.

The videos didn't impress me much although there was an improvement. The music track was considerably easier to listen to over headphones compared to regular stereo. Technically, I came away with the notion that it only works in 96/24 and below and not the 192/24 where DVD-A has quality comparable to SACD.

So how would this be delivered? One could build it into one's player or buy DVDs with special tracks mixed for DH.

My fantasy is a special processor loop to plug into the tape loop in a receiver. It would need A/D converters to get the music into the digital domain than the Dolby processor to work on the digits and finally a DAC and probably an op-amp to feed back a line-level signal into the receiver. One could do this just for stereo or maybe have 6 channels for the Dolby chip to downmix to a stereo headphone signal.

That way, one could listen to any stereo or 5.1 source with DH - FM, LP, CD, or whatnot. Most of it could be advanced DIY but one would need Dobly Headphone processing chips and don't know if they are available.

What is still unclear is how this differs from binaurial (sp) recordings or is it just a synthetic version?

Any thoughts?

I did a little experiment yesterday...and I was pretty pleased with the results....I found a way to use DH with foobar2000 via a "wrapper" for DH. If you own DVD software package that has DH, you can use a wrapper to add this to foobar2000.....just feed a 5.1 mix into foobar2000...and out comes a stereo DH encoded stream (via the wrapper plugin)....plus, you can use the diskwriter function within foobar2000 to "render" the files encoded in DH....which should come in handy for demoing my surround mixes to people without surround systems.:sun

I did this previously with using WinDVD and AC-3 files.....which is not the greatest fidelity...but with this foobar plugin wrapper....I can use uncompressed (or lossless compresed) up to 24bit 48k 6 channel files which sounds oh so much better.

Hi,
DH is included as a DSP on my Denon 5803 and I find it excellent for late-nite. I picked up a relatively inexpensive pair of Senn PXC250 which advertises Bass in the teens. They are also small so not too tiring weight wise.

The Denon manual says you can plug your headphone jack into a recorder and create your own 5.1 mixes.

Question is, what do you listen to it on?

Anyway I have over 300 dvd-a/sacd discs and listen to may of them in stereo by choice.

I find it neet though when I play the DTS program of a film and the face of the Denon go's DTS + DolbyH.

Peter M.

I can listen all the time surround music via headphones and my Creative Audigy2 soundcard and/or WinDVD from Intervideo.
There are many head transformation functions - CMSS, Sensaura, Dolby Headphones, Interactual headphones, SRS, etc... Also Bose has a system with 3 channel surround... My HK receiver has Vmax that does the same (5.1 in stereo).
And I can compare them with the real thing in my 5 speakers.

Is not the same...

Hi,

I've restricted my use of DH to late nite movie and tv watching and although it's more realistic and somehow less fatiguing than 2ch essentially it's 5.0 if like me you subscibe to the theory that .1 is felt more than heard.

My processor turns off all the speakers as soon as I plug into it's headfone port. That said, would anyone know how I might be able to incorprate a BassShaker for the .1 and still use DH?

Thanks,
Peter M.

I just finally took a chance on Dolby Headphone, bought the little JVC pocket-sized adaptor. I think there will be a lot of people disappointed with this when playing 2-channel sources using the DPL-II mode...BUT, and this is important! Give it a chance! At first, I thought it sounded worse than stereo, although less fatiguing, but the image was just not there. HOWEVER, remember, locating a sound is NOT done by the brain solely based on audio. When you listen to headphones, you (a) KNOW that you are doing so, and (b) are often looking at something entirely un-related to the sound. When you are listening to speakers, you know where those speakers are, and this biases the brain's "decision" as to where the sound is coming from. After reading a few reviews, and hearing better results reported for movie use than music, I figured there HAD to be some psycho-acoustic things going on here.

Sure enough, after listening with eyes closed for several minutes, forcing the brain to go ONLY by the directional cues provided by the processor, the image DID start to form. Where the lead singer had first seemed to be above the head somewhere, it became out front, as it should be. (It also helps to "imagine" the center channel being in front of you at the same height, and giving the noggin a few minutes to agree) Once the image formed and stabilized, I felt as if Three Dog Night was giving a personal concert just for me!

True, this is no match for properly spaced (and fed!) speakers, but with a little effort to "train the brain", it can be very satisfying all the same.
Since I bought this mainly for use with a portable MiniDisc or FM radio, the size was a big (OK, small :>) advantage...then realizing that the coding done by it still leaves just two channels, I decided to just use it as an "encoder" when RECORDING the MiniDiscs, so I don't even need to take it along for playback.

As for binaural recording, I have done that for years, usually jamming small electret microphones into my ears. At times, the results CAN be spectacular.
BUT, everyone has different ears, different brains, and most importantly, different Head Related Transfer Functions, so some people will listen to them and not seem all that impressed, while others get big-eyed and say "WOW!" or stronger words. It is also important that the PLAYBACK transducer's diaphram be at about the same position as the microphones. This presents a problem, of course, play back through ear-buds (yech!), or position the mikes a bit farther out from the middle ear, which then lessens the effects of the outer ear on what it hears. All the same, Binaural CAN be very impressive! I played a thunderstorm recording for my mother...she felt the rain on top of her head.

I DID record a quad playback through speakers, using the in-ear mikes, and played on MY head you can easily tell front from back, but I think for just improving on "in the head" stereo, DH is a better alternative. I will definitely be using it for all portable listening from now on.

BTW, PLEASE don't rush out, buy condenser elements, and jam them carelessly into you ears! I am NOT responsible for earaches or worse! Such mike placement can be somewhat uncomfortable. If it isn't worth the pain and risk to you, PLEASE don't do it! If it IS, use extreme caution!

TB