[]|[ GorE]

HEllo there fellow head-fiers !

I have created a Dolby Headphone mode 1 impulse that you could use in foobars convolution plugin.
Select Auto adjust and reduce mixing volume by 2.9 db.

Heres the link :
http://www.filefactory.com/get/f.php...0e06346fa718ef

Please use it and give feedback.
Oh,almost forgot.
Push Convolver AFTER the Resampler(if you are resampling) in the DSP Stack,since the impulse response is a 48000 Hz file.
Cheers from Dubai !

 

[breez]

Can you provide it as a wav or losslessly compressed file?

 

[thomase]

How did you get this? Did you measure it or otherwise reverse-engineer it? I thought the "magic" of Dolby Headphone was not necessarily the impulse response but the algorithm used to implement the associated 7000-tap FIR.

Is this file really a 145ms impluse response, and if so, is it possible for this to be computed in real time with foobar's convolution plugin?

 

[]|[ GorE]

What i did was open a 24 bit Unit Impulse file using SoundForge,and converted its bit depth to 16 bit and resampled the file using the highest interpolation accuracy to 48,000Hz and saved it as a 320Kbit Mp3.
I also added 2 seconds of blank space on either side of the impulse to avoid incorrect output(previouslu obtained by me) from Dolby Headphone.

There are reasons why i performed the above conversions:
WinDVD 7 and PowerDVD 6 can only apply Dolby headphone to mpeg3 audio files and both internally resample the audio file to 48000Hz before sending it for processing to Dolby Headphone.

Next,I played the file using WinDVD 7 and recorded the "WHat YOU HEAR" output using SoundForge.
The result is something that you can download now.

The file currently posted is inaccurate.I will upload a new improved set l8er.

Oh,i just remembvered that PowerDVD 6 supports MLP decoding.Maybe i could produce a MLP impulse if i could get SOundForge to open it...........

Anyway,keep the feedback coming !

 

[]|[ GorE]

Just made an improved impulse response in 24 bit WAV but cant upload it for 24 hours since filefactory uploads are offline.

 

[breez]

I can host it on my ISP's webspace if you mail the file to me (lauri.mela _removethis_ @gmail.com)

 

[sgrossklass]

Resampling a dirac pulse isn't a good idea, that way you'll have the impulse response of the resampler in there as well. And that isn't insignificant - look at it in Audacity with a magnitude display in dB. (A "proper" dirac as far as possible should consist of one sample at 0dBFS while all the others are zero.) To convert this correctly, you must only *change* the sample rate. (Open new project, change its sample rate to 48000 Hz, import audio, change track's sample rate to 48000 Hz.) Be sure to also look at the final MP3 result to see whether it has any resemblance to a dirac. You may have to select a pretty funky set of encoding parameters to get that halfway right.

Re: file format, best use FLAC or somesuch.

 

[Sovkiller]

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[thomase]

Quote:

Originally Posted by sgrossklass Resampling a dirac pulse isn't a good idea, that way you'll have the impulse response of the resampler in there as well. And that isn't insignificant - look at it in Audacity with a magnitude display in dB. (A "proper" dirac as far as possible should consist of one sample at 0dBFS while all the others are zero.) To convert this correctly, you must only *change* the sample rate. (Open new project, change its sample rate to 48000 Hz, import audio, change track's sample rate to 48000 Hz.) Be sure to also look at the final MP3 result to see whether it has any resemblance to a dirac. You may have to select a pretty funky set of encoding parameters to get that halfway right. Re: file format, best use FLAC or somesuch.

But since he is starting out at 48khz, it probably won't resample anyway, right? Anyway, the MP3 encoding is probably more problematic.

I have more problems with this though... Are you trying to record the impulse response for more than 1 channel? 2 or 5? Also, according to Dolby Headphone literature, the impulse response should be on the order of 100ms if it is really convolving using a 7000-tap FIR. Can foobar convolve an impulse response this long in real-time?

 

[]|[ GorE]

Yes,the idea of setting the playback rate to 48000Hz instead of actual resampling did strike me,but i didnt do it since i was worried about the slope of the impulse response getting changed.

And yes the use of mp3 does distort the impulse quite a bit and so far i have been unable to get rid of the distortion.

And i guess,i could create an impulse response 145ms wide using Sound Forges pencil tool.

I will see what i can do.

 

[]|[ GorE]

SHould i use an "Unit Impulse" or should i use " Dirac Unit Pulse" ?
And should the impulse finally generated have any zero amplitude spaces or samples on either ends of the impulse ? That is should the file have any blank data before and after the impulse ?

Please reply ASAP.

 

[]|[ GorE]

Finally got an impulse i am moderately happy with.
I think i can say that my impulse is UNABLE to create any crosstalk.Theres something about DOlby Headphone that creates a sense of "space" that my impulse cant provide.
However,the impulse does generate a good forward and center image and changes the tonality to match that of a speaker.

 

[sgrossklass]

Quote:

Originally Posted by ]|[ GorE I think i can say that my impulse is UNABLE to create any crosstalk.Theres something about DOlby Headphone that creates a sense of "space" that my impulse cant provide.

That sounds reasonable for per-channel processing. You'd have to use something a bit more sophisticated to reproduce what DH does. Then you would need to measure the impulse responses (in stereo) for both left and right input signals separately.

 

[]|[ GorE]

Sgrossklass,any way i can do what you say ?