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John Dyson

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About John Dyson

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    Audio DSP/SW developer, sometimes listener

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  1. A private correspondent on this forum had decided to try to decode a rather difficult recording -- 'Even in the Quietest Moments', and the result of the attempt was a discussion that I think might be helpful for other users of the DHNRDS FA mode of the decoder. The context is that the OP didn't like the results of decoding 'Even in the Quietest Moments', either too harsh with just --fa, and too soft with --fa=2. Note that as of the time of this posting, I haven't gotten a response for this help, but some of this commentary can be VERY HELPFUL for *advanced* decoding of difficult material. Most material DOES NOT require this level of detail!!! The first post is my FIRST response to the OP's troubles (and he is doing good -- just having troubles), the second section is a second response that attempts to give greater technical details: ======================================================================================= FIRST RESPONSE: Ahhh... Even in the Quietest Moments is a real problem because of that horrid 'chorus effect' 'enhancement' in the first cut. I have a raw very early release of the CD -- A&M 394 634-2, which seems to be pure feralA. (FYI) Also, have several other remasters that are all mangled. Just a caveat. Even in the Quietest Moments is an ADVANCED decoding effort -- probably one of my more difficult selections in my own collection. This note, however rambling will talk you through decoding my own copy... Before reading my rambling description -- when you use the --fa=XXX switches, if you use the --fd switch also, it will give a dump about what feralA EQ filters are being used. It might help give you a 'feel' about what is going on. ---------------------------------------- Given the above 'state' of the recording, on my copy -- the raw --fa allows the chorus effect on the first cut to be very edgy and overwhelming, even though the other Supertramp CDs seem okay with just a --fa... Here is my idea... Try this "--tone=-13.37", which decreasing the threshold A SMALL AMOUNT sometimes tames edgieness a little. I suggest that small change will NOT be enough. Next, try this: "--tone=-13.37 --fa=4", which might tame the sound just a little unevenly, but will be improved a lttile. The --fa=4 swich adds in a 12kHz filter before decoding -- that is a relatively small amount. Usually, if a filter is needed, --fa=2 is a good choice, which is 6kHz -- but IS too much for my copy of Supertramp also. On my copy of the CD -- --fa=2 is like a wet blanket. Paradoxically, decreasing the effect of the 12kHz filter, but keeping it at 12kHz seems to be the best improvement for my copy of 'QUIET". The --fa=4, with the 12kHz 1st order LPF is a full LPF all the way up beyond the Nyquist frequency. Instead, that evil enhancement sounds more 'stable' if you stop the LPF at 18kHz... On my copy, I can actually hear both edges/both copies of the enhanced (pseudo-chorus effect) vocal after using the following command: "--tone=-13.37 --fa=4 --fhh4=18000 --normal" Which is a 12kHz LPF, stopping it at 18kHz... YOU MIGHT prefer "--fa=3 --fhh3=18000 --normal" instead, but I feel that the recording MIGHT be filtered a bit too much. It MIGHT be better, but my mastering-hearing is not all that good -- I have poor artistic skills. I try to be careful. Perhaps the '--fa=3 --fhh3=18000" might be better, but if I was demoing to picky audiophiles, I'd tend towards the wider '--tone=13.37 --fa=4 --fhh4=18000' sequence above, but use --xpp also instead of --normal, which kicks in the anti-MD code, but REALLY slows down the decoding. I haven't fully explained using --fhhN in the 'usage' docs, but the more complete document does talk about the '--fhhN' filters cutoffs. Using '--fhhN' is a more 'advanced' usage, but the Supertramp 'QUIET' album is a very advanced, somewhat tricky challenge when compared with most other albums. 'Carly Simon' also has similar enhancement in her vocals, but usually end up sounding smoother. My decoding example is run at the --normal mode, but the --xpp mode will be a little more clean (almost imperceptably better). Attached is a truncated copy of my .flac results. (mp3 tends to filter out the edginess -- not appropriate for this example.) Please let me know if this 'diagnosis' / 'prescription' helps your CD.... If your CD does't sound much like mine -- I can try one of the other exemplars in my collection and try to get good results with those. However, my example comes from a PRISTINE feralA CD. If yours is pristine, but ends up sounding different, then the mastering engineer just might have used different feralA EQ parameters... I can help you if you send me a snippet, and try to get good results as a learning experience for both you and me. =================== SECOND, FOLLOW UP TO FURTHER EXPLAIN THE "MAGIC" about --fa=N, etc.: Clarification why I added the --fhh4=18000. First note that the --fa=4 invokes the filter#4 which is normally a 1st order LPF at 12kHz, just keep on going down -- no stop to the rolloff. When I added the --fhh4 switch, that set the 'stop' for the rolloff on filter #4. Why does that even-out the sound of the vocal enhancement? Tricky stuff, but let me 'splain about DolbyA in detail further down, but basically when increasing the levels SLIGHTLY in the 9k-20+kHz range, it can suppress the 3k-9kHz range just slightly -- DolbyA is like that. The 3k-9kHz range 'fights' the 9kHz-20kHz range because of an inverse decoding relationship. It is also a slight cause for increased distortion during DolbyA decoding, if it is not done correctly. Explaining about the filters: There are 4 normal filters, and a 5th special filter -- don't use it, it will be automatically invoked by using the 'spcN' modes. All 1st order: Filter0: 3kHz LPF FIlter1: 4.5kHz LPF Filter2: 6kHz LPF Filter3: 9kHz LPF Filter4: 12kHz LPF I believe that the Filter0 (3kHz) and Filter1 (4.5kHz) stop the rolloff early, but the rest just keep on rolling off. (You can check it by using the --fd switch.) You can fully control the filters by usign the '--fhN' or '--fhhN' switches, where '--fhN' is the start of the rolloff frequency, and '--fhhN' is the stop of the rolloff. It is usually best to NOT change the '--fhN' value, but you can if you want. I chose the frequencies for a very good reason. However, you JUST MIGHT find a case where a rolloff at 7.5kHz would be better. Then, I'd grab Filter2 or Filter3, and re-configure them with '--fh3=7.5k', and now the Filter3 starts at 7.5k, simple as that. (And yes, using 'k' works.) About DolbyA.... There are two overlapping HF bands, 3kHz to 20+kHz, and 9kHz to 20+kHz. These bands overlap based upon an approx Q=0.450 difference at an 9kHz transition frequency. These bands represent COMPRESSORS in the reverse leg of a feedback loop (theoretically.) (Those compressors in the negative feedback result in an expansion or decoding of the DolbyA material) When the 9k band has more signal strength in the feedback loop, then that will tend to suppress the behavior of the 3kHz to 20kHz band. (Note that I usually name the 3kHz+ band as HF0 and 9kHz+ band as HF1 in my commentary, even in the source code.) Those two expanders have time delays, and there is a critical 'dance' between them on a varying audio signal. If the expanders do not dance a very well choreographed dance, then the result sounds a little distorted. ALL normal DolbyA HW decoder do NOT dance the dance very well. The DHNRDS is excruciatingly accurate and precise in its dance... This is one of the attributes of the DHNRDS that produces more transparent results. So, there is an inverse, suppressive relationship between the HF0 and HF1 bands, and the slight HF1 boost by stopping the filter rolloff at 18kHz actually produces a very subtle suppression of the HF0 band, and also just happens to make the DHNRDS decoder 'dance' more precisely :-). Anyway -- this is both the long story, and longer story. YOU DO NOT NEED TO FULLY UNDERSTAND THIS FOR SIMPLE DECODING -- but 'Even in the Quietest Moments' opend up a can of worms :-). John 01-Give A Little Bit-snippet.flac 9.27 MB · 0 downloads
  2. I agree about HDtracks -- they just pass on what is given to them, and don't even trim off the noise, splats etc above 20kHz. Some recordings have real info above 20kHz, but I doubt most pop material does. When using the DHNRDS FA mode, the actual recording can be recovered from the signal -- instead of that CD mismastering stuff. I have found also that MFSL does true mastering, but on the few examples that I have -- I can do significantly better than the remastered MFSL version, start with a CD, do the corrective EQ, and the decode properly with DolbyA -- that is what my little project is all about. The software works, but the key to good results is that the recording must be a raw CD, no ham handed remastering attempts. You want the raw, EQed DolbyA recording as sold early in in the CD timeframe. Up until about 1994, you were pretty safe to get pristine stuff. However, HDtracks still sells some unmastered stuff -- like my Carpenters singles album. I am currently decoding it right now and going to put it up on a demo site soon. (Just a few selections.) The difference after proper DolbyA decoding is profound. John
  3. I don't have a website, but that might be a good idea. I am 100% overwhelmed right now, but that might be a good thing to get started in the near future. John
  4. I could do that from my own recordings -- but the collection, even though in some respects is big, is such a small part of the CD world. I'll definitely do that in paralell for the DHNRDS FA distribution, but the crowd-contributed approach is the only way that it can be viable, and frankly there aren't all that many FA users YET. I have had a hell of a time making it simple enough to use. It is down to approx 2 parameters, but sometimes up to about 4-5 parameters. (They are reasonable, not complex.) Before 2-3 months ago, it required perhaps 20-40 parameters to do a decode. There is a variability to the required decoding paramters, but there is also a very common, consistent structure -- that is why usually 2 parameters does the job, but this tijuana brass thing I am doing now required about maybe 3 or 4 parameters. (Most parameters are numbers between 0 and 5 or 0 and 8, only one floating point number -- like -13.40 or somesuch.) It is down to a motivated person being able to do really good decoding operations in a few minuts. Perhaps requiring an hour or so of learning at first. John
  5. The DHNRDS FA mode decoder has the ability to extract something VERY CLOSE to the original DolbyA master tape from many CDs. Then, the decoder does a very accurate, specially clean DolbyA decoding process (true decoding, not the ham-handed EQ done by some plug-ins.) The variable is that the EQ is somewhat different from recording to recording, but the necessary EQ needed to convert back to DolbyA is usually fairly consistent in some aspects, but then a few parameters are somewhat variable. SO, I have a fairly high quality method that undoes the simple EQ method used to make DolbyA material sound tolerable, then take that re-created DolbyA, then effectively produce a master tape from the CD. It sounds impossible -- but that historical 'Digital sound' that appeard when CDs came out, that is actually EQed DolbyA, not actual DolbyA decoding and mastering. My recent (2-3yrs ago) purchase of the Carpenters singles and 'Unlimited' version of Band on the Run, both of them from HDtracks, are the EQed DolbyA, and have NOT been DolbyA decoded. I can demo on request, and I have an interesting 'Tijuana Brass' copy that is also properly decoded DolbyA -- I am just not sure about the higher end of the spectrum -- I need some reviews. I cannot hear about 14kHz, so I need someone to tell me if it is okay... I can make demos available, there is some stuff on Dropbox right now. (I have literally > 100 CDs of this ilk. Many people also do, but just don't realize it.) John
  6. The 'remastering' cost is getting down to NIL now. The deocder does most of the tedious stuff, and even really good results can often be achieved in a few minutes (really.) On some recordings, there is benefit to spending maybe an hour, but not that many are all that eccentric. I got the decoding EQ down to some fairly straightforward stuff. The problem with the 'crowd sourced' approach, even though it appears to be REALLY cool, and I like it... Buuut.... There are so many varied releases of each recording, and recordings are often 'normalized', which screws up the calibraition, or worse -- normalized on a per selection basis. When they do that, it causes a lot of work, because the calibration has to be tweaked on a per selection/cut basis... That IS a lot of work. Also, some recordings have been meddled with, and a lot of recent recordings have been 'newly remastered' (translated: destroyed). I have tried to put together a list for myself as an experiment -- but even the list that I publish along with the decoder is almost useless for those who don't have the versions of the recordings that I have. Using ABBA as an example, I have perhaps 10 CDs per album, and except for Polar/Polydor, each one has different levels on the CD!!! Each CD, except for certain groupings, sound different. If one starts with a stable source as from a distributor, then it is possible to make a stable remaster (which is a set of between 2 and 5 command line parameters, most of the time it is only one or two.) John
  7. I had been thinking about a possible work-around for the IP issues associated with licensed selling of pre-recorded materal, but doing further remastering without the 'remastering distributor' losing control. That is, I was informed in these forums that places like HDtracks/others that redistribute recordings must eventually offer their own redistributed modifications to other licensed redistributors. At least, that is the jist of how I understand the situation. ----------------------------------------- Problem: license encumberances against those 'remastering' when normally licensed a distributor eg HDtracks or downloading services. Answer: allow the end-user do the remastering as an automated installation process, however a little more slowly WRT installation time. ---------------------------------------- Discussion: It is probably clear to you that I am cluless about licensing terms on recordings -- geesh, I barely understand GPL/LGPL and the licensing scheme that I actually prefer -- the BSDL or other freer/less encumbered terms. (I come from the viewpoint as a beneficent developer, not as someone who is trying to profit & offer usage at the same time.) Since a redistributor who 'remasters' the material that they sell 'might' be required to offere the 'remastered' material to other licensed distributors after a certain time out, then the cost/overhead of the remastering effort might have to be spread over too few sales of the results. Also, the competitive advantage ends up being NIL very quickly. With the current obvious scheme, it might be difficult to pay back the cost of remastering, even if it isn't expensive to do, and even if the motivation isn't really about profit -- just trying to create a market nitche. This is not something that I have any interest in creating a business -- but might be a possible scenario for organizations similar to HDtracks. So, when I write about this -- it is NOT about me creating a business, but instead it is about considering ways to leave a legacy, that is -- something good, nice and pretty for the rest of time. ----------------------------------------- Here are more details about the idea... Clarifying that the DA/FA/etc software is MINE. Any encumberance to the DHNRDS project is that the DHNRDS project has rights to redistribute whatever versions I give them, and I do intend to always contribute newer, improved version of the DHNRDS DA/FA and the upcoming C4/DB/DC etc versions of the decoder. I am willing to offer redistribution rights to people who might do something good with the decoder, even IF they might also profit to some extent. After recognizng that the software is mine, and I have the right to give away derived versions of the decoder(s), I can offer the software and any associated derived works to others (licensed music distributors/potential remasterers) for them to redistribute. The 'remastering' process using the FA decoder is 'constant' once the parameters are chosen, and each parameter set is not generally unique to each recording. That is, multiple groups of recordings have the same or similar decoding parameter sets. I believe that this general lack of uniqueness about the decoding parameters would keep the 'installation' or 'remastering' parameters themselves from being derived works of the original music recording. I propose that there is a way of distributing improved, remastered material WITHOUT distributing the modified recordings. The method is straight-forward and maintains IP control by the 'remastering/distributor', because there would be an INSTALLATION process which starts with the original, unmodified recording from the distributor, along with a pre-programmed version of the FA decoder, which then does the remastering as an installtion process. The end user/music listener does NOT need to 'tweak/tune' the decoder, but instead simply uses it as a Windows (or whatever) installation program... The customer ends up with a copy of their recording, and an updated remaster of the recording, with NO redistribution of a modified recording. The installation/at-home remastering software is licensed by the redistributor as an INSTALLATION package... Do you think that this would be practical? That is, open up a niche for a licensed music distributor, to be able to distribute remasters under their current distribution terms? The amount of work vis-a-vis 'remastering' would be the same as if the remastered material was distributoed, and the end user actually does the 'remastering' by virtue as an installation of the recording... What do you think? -- I am looking for positive solutions, not so much about 'no market for it'. I understand that possible aspect also. John
  8. I plan to make a new version of the decoder ready with the metadata pass through Thursday, Friday at the latest. Trying to have something ready for the weekend. I have been doing test decodes for part of the day today, and have some really clean, simple results. During my mostly rest-day, I have been thinking/worrying about how 'intuitive' the EQ scheme is - that is, not very intuitive. I'll also be documenting the EQ a little better. This is a fine line of complexity vs. clarity -- and I cannot project my ability/inability to think on other people, so I have to guess what kind of docs are needed. (I have a very very bad, damaged short term memory ability -- yet my thinking and long term abilites are crazy sophisticated -- I cannot guess what is easy or difficult for people trying to use this software tool.) GUIDANCE might help me write something that could help users with the decder. If you have any ideas - tell me. Since I do know that most people see things better in pictures, or clear/clean organized text -- I'll really try to use a WYSWYG editor to produce more readable docs -- with some kind of organization. I really do feel that if someone understands the NEED vs what is PROVIDED -- that the deocding EQ choices will be more intuitive. John
  9. Hi John,


    I have attached some wav files.  Hope this helps.



    1-05 Another Brick in the Wall, Part 2.wav 06 Billie Jean.wav 02 Dreams.wav 01 Missionary Man.wav

    1. John Dyson

      John Dyson

      Got them.   I am pretty sure we can get the metadata pass through by about Thur, Fri afternoon at the latest.   The goal would be to have a new version of the 'toy' ready by the weekend.   There will be a bit more documentation, minor refinement, but no calibration changes.

      I plan to document what the EQ modes really do -- so it gives a better 'feel' of what is going on.

      Going back to the forum and reading that -- will answer more there.

      Also, will be providing some possibly interesting demos tomorrow or so.




  10. Yea -- I'd like an example (one or two variants) of the metadata that you want to keep. Interesting because I didn't even think of it, and it is kind of sad that SOX doesn't support it either. Might take me a few days as the architecture isn't really set up for generic metadata. If I can get an idea of expectations, it might be less of an onerous situation. Like, if it is a specifc kind of metadata, even though it might have lots of instances -- that will give me an idea about what is wanted. I do have some other examples from my own sources (old wav files), but if you want to -- the .wav files would be better... I doubt that I can add .flac support without licensing issues. (I want to keep ownership of my IP, no GPL -- LGPL is okay if it is built-in to the OS, but -- the licensing requires some care.) It might have been easier to use someone elses .wav package, but anything good was licensed in a way that would tie me up a little. Eventually, I plan to give away the source, but not quite ready yet. John
  11. Yea, the default is -13.30, but probably should be -13.35... The difference isn't much, but is just enough to detect. John
  12. Oh yeah, the conversion of the flac metadata is incomplete in SOX. When I produce flac files, even though the DA decoder makes its own metadata, I have to manually re-create some metadata for flac files. Much of it is about SOX. On the other hand DA decoder maintains SOME of the metadata, esp the BEXT items for professional purposes. It will append to already existent BEXT data, or create its own. Other metadata, some of it gets thrown away. If you think that is a major deal -- I might be able to add some support to maintain more of it. When originally doing the DA decoder, I was focused on the BEXT stuff (it needs special handling), and ignored the other stuff -- possibly wrongly. I truly forget, and will look into it. It shouldn't be too awful hard to add some other data items. As I wrote before, the .wav file handling is knarly. :-). John
  13. Actually the opposite -- -13.25 is larger than -13.40... It mucks me up also, because intuitively the numbers seem opposite because they are negative. But, basically to explain, at HIGHER threshold levels (like -12dB) , the HF gain (and gains in general) will decrease. At LOWER threshold levels (like -14dB) the gains in general will increase. On DolbyA decoding, the gain is on a 'hinge' which is the calibration level. Signal levels ABOVE the 'hinge' will be close to 0dB (except at MF, where the threshold is 10dB or so lower), below the 'hinge' level, the gain will tend to decrease at approx 1dB for every 1dB level change down to a min gain of -10dB at up to 9kHz and -15dB at 20kHz. This 1dB gain change for a 1dB level change effects an APPROX 1:2 dB level expansion. John
  14. I didn't realize that it was that screwed up... Going to the trouble for a remaster, and then giving up the rights... Well, if done correctly, and I am NOT claiming that I have done so -- it requires experts to do so -- it would improve the general ecology of prerecorded materials -- but with zilch benefit to those who invest the time/effort? Thanks for that information... You know also -- it is unrealistic for HW/SW at current state of the art to automatically remaster, so we are stuck with what we have? It is really, really sad. I know that I was tilting at windmills, just not knowing how pathetic the situation is.... Another method to 'improve the music': -- but a bit complex, is a recording + software package, all boxed together, ready to *automatically* run/decode on a Windows PC, like a download/install process.? (I am NOT interested in $$$ profit motive, just interested in the music.) I wonder if that could be legal? John
  15. Just IMO -- NOT intending on shilling my project, but if the distributors -- esp HDtracks -- would actually provide much higher quality than otherwise available, not just more bits, then they might really expand their market and create loyalty. As it is, a slightly (very slightly) clearer version of a 'CD with more bits', with some of the noise/splats/errant signals above 20kHz -- should be filtered out anyway, is not a compelling purchase. If there is something that actually makes a product SUPERIOR and not just better in a very 'esoteric' way, then they just might make a real place for themselves in the market. John
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