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Dolby B/C decoding open source software

Jim Audiomisc

Jim Audiomisc

pfm Member
Barry Fox has been asking about this recently and it has drawn my interest back to the question. Is there already an open source software Dolby B (and C) decoder?

If not, I'm wondering if it is time for someone to have a go.

I do have some documents that help define what is needed, but am also wondering who else here may have some info.
 
Thus far, I can find loads of stuff on Octave, but haven't yet found a specific Octave program for Dolby B (or C) decoding. If someone else know where such source code is, please let me know.
 
Thanks! :) I'll have a look, and let Barry know.

That said, I must admit I sighed a bit at it being in Pascal. One of the languages I never bothered to even try to learn! 8-]

I do have a paper by some academics who say they did an Octave version, but they don't seem to have made it available.
 
I got an error trying to access the 'hightail' address.

The snag with the second is that Barry is looking for an open/free source version. And my interest would be in part to check the code to see how it works and if it seems 'to spec'.

Given that the patents have lapsed it seems a no-brainer that *someone* should have done this. Thus far all I have found is the Pascal example and 'rumours' of one in Octave, but which I can't find anywhere! TBH I'd be willing to learn some Octave as it might be handy, but I doubt I'll ever have any other interest in Pascal. :)
 
Jim Audiomisc said:
The snag with the second is that Barry is looking for an open/free source version. And my interest would be in part to check the code to see how it works and if it seems 'to spec'.
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Sure.

But it is good to know that a cheap and functionally complete app is out there, not.

Further, as it can be operated with file-in/file-out, it can serve for studying Dolby, or for reverse engineering any other solution.


Something else, only slightly related: I have known Barry Fox writing technically in HFN since I was a lad. His photographs always showed a gentleman of, say, rather advanced age. All these decades later he is still active ...
 
Software? No no no! :D

Modern opamps, or discrete circuitry, and the latest greatest VCA's from the likes of THAT corporation should make a pretty ultimate Dolby system.... and the proper analogue way:)
 
Werner said:
Sure.

But it is good to know that a cheap and functionally complete app is out there, not.

Further, as it can be operated with file-in/file-out, it can serve for studying Dolby, or for reverse engineering any other solution.


Something else, only slightly related: I have known Barry Fox writing technically in HFN since I was a lad. His photographs always showed a gentleman of, say, rather advanced age. All these decades later he is still active ...
Click to expand...

Well, yes, the Pascal prog, and that there is - somewhere - an Octave prog is good to know. But I suspect that for more general open source use something in a more widely used language like 'C' would be preferred.

I'm fairly sure Barry is older than me, but I'm much too polite to ask. :) Yes, he still writes items. Some appear in HFN. He's been raising this issue recently.

I could have a bash at translating the Pascal. But TBH I'd probably find it easier to work out what to do from looking at the circuit diagrams Dolby issued for 'home constructors' many moons ago. I find reading a circuit diagram easier than reading Pascal! 8-]
 
Jim Audiomisc said:
Well, yes, the Pascal prog, and that there is - somewhere - an Octave prog is good to know. But I suspect that for more general open source use something in a more widely used language like 'C' would be preferred.

I'm fairly sure Barry is older than me, but I'm much too polite to ask. :) Yes, he still writes items. Some appear in HFN. He's been raising this issue recently.

I could have a bash at translating the Pascal. But TBH I'd probably find it easier to work out what to do from looking at the circuit diagrams Dolby issued for 'home constructors' many moons ago. I find reading a circuit diagram easier than reading Pascal! 8-]
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Please do pass on my appreciation and admiration for Barry's work in the fight to make a biography of Alan Blumlein possible :)
 
IMHO I hated Dolby It just didnt do anything I liked, Dolby A & B dull and lifeless Dolby C better but pumping effect???
I much prefer tape recording on a R2R in its natural form, it doesent f*ck with the sound
Alan
 
I find Pascal code easy enough to read, it's C++ that I struggle with.
The problem with all the Dolby variants was the lack of any public explanation of its operations. They always went down the trade secret route rather than patent protected
 
wd40addict said:
I'd disagree on this, at least for B, it's all laid out in US patent 28426.

+1 for Blumlein biography work!
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I've not read the patent, but IIUC Barry said the patents do the usual "claim all, describe nothing" trick. i.e. give some 'examples' that aren't necessarily the one they use.

However we *do* have the circuit diagrams for a 'B' encoder/decoder. If someone wants to have a bash as translating the Pascal into 'C', please let me know. I'll probably find using the circuit diagram as a 'definition' easier. :)
 
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