Hi, MPC so far looks perfect for a community project I am involved with. But can I just ask, since the MPC/MusePack technology is based on MP3 (?) is there any associated patent issues?

Thanks for any info!

Well there are pattents involved that have not been given full attention. Many of them expire soon. And many of them might not really apply to what you are looking to do. So what exactly are you looking to do?

According to Frank Klemm (one of the primary developers of MPC), it currently implements components of at least one patent (a Philips subband-related patent). He posted a bit about that in a thread from August here at HA: http://www.hydrogenaudio.org/forums/index....=ST&f=11&t=2910

From his post it sounds like this includes both the encoder and the decoder (he says removing the patented techniques would increase CPU load of the decoder significantly), so that would seem to make MPC unsuitable for anywhere that patent infringement might be an issue.

Hi, thanks for your replies, and the reference.

Just to clarify: No, patents are not really an issue with what we are doing (AFAIK) but it is just a "preferred" thing to use a patent-free codec. Not a huge issue since otherwise, we think MPC is perfect for what we want in all other respects.

Just for reference, we are completely preserving classic Amiga games, some of which included audio cassettes. Everything must be perfect, and some respected "audiophiles" suggested that along with very good stero equipment and sound card, we should also use high-bitrate audio compression. Which initially surprised me with tapes, but apparently it is quite important. You guys probably know this better than me anyway.

Anyway, the end result is that we will encode these tapes, and distributing the resulting files with the rest of the preserved game (game disk image + box & manual scans) to original developers, sites with permission to distribute the game, and people we *know* own the game (our contributors). Please note, this is all completely legal - we actually feel very strongly about that.

If you are interested, see the site in my signature for more information about C.A.P.S. and what we do.

Musepack was based on MP2, not MP3.

The patent status is unclear:

1) there is only one patent that is reported to really apply
2) neither me nor Frank Klemm have been able to track down what exactly that patent would be
3) the original MPC developer was never able to track down someone he could license it from
4) the rights on MP2 patents seem to have been sold several times to increasingly obscure companies
5) the patents themselves are already expired or will expire very soon in several countries

Based on all of this, I think it's actually quite safe to use MPC.

Thanks! I am glad the situation is better than I first understood.

As I said, MPC looks completely perfect for what we need it for.

You never know, perhaps it will even raise its profile a little. Though probably not enough that you would notice.

Fiath, if you want a perfect copy then you must realize that MPC is a lossy codec. Although it may sound identical or almost identical to the original sound to most people, it is not the same, therefore you will not have a "perfect" copy. I would instead recommend that you use FLAC which is a lossless format. Although the files will be larger than with MPC they will be identical in sound to the original.

I would also suggest that you would want to carefully test any perceptual lossy codec very carefully before using it. There may be frequencies thrown out or phase information lost or artifacts added that may be completely inaudible but could compromise the data extraction.

WavPack's lossy mode might be ideal. It is close to perfectly efficient at preserving exact waveforms (without reference to how they sound) and you can simply modify the bitrate to get exactly the S/N ratio required for reliable operation with your setup, and it works at all sample rates. It's also completely open source and AFAIK patent free.

www.wavpack.com

The way I read Fiath's second post, the cassettes were audio cassettes, with audio on them, not "datasettes" with data modulated onto them. The Amiga had a built in 3.5 inch DD floppy drive, so I very much doubt the program data would be on the cassettes supplied. If it's audio for human consumption, MusePack is a good choice for lossy compression if disk space is fairly important. A lossless format like FLAC (or indeed Wavpack lossless) is a good idea for archival backup as it would enable you to make adjustments to the sound later (e.g. noise reduction) from the best digital source you have, even if the analog tape is degraded.

Yes, sorry, I should have explained that better. DickD, you are spot on. The audio cassettes are just extras to the game and not game data. They may have sound-track music, or other things, so a lossy codec is wanted because we don't really want to distribute 50Mb files - as MPC appears to be the best there is, it is perfect for our needs.

And indeed were planning on keeping a "master" FLAC copy of each one that won't be distributed with released games, but can be used if anybody wants an unofficial MP3 or Ogg version. But I am glad we know that this is a recommended thing to do.

Thanks again!

Fiath,

mppenc 1.14 is a good choice (link in my sig) as it's a stable beta and won't add "Unstable/Experimental" to the profile tags in your files.

mppenc --quality 5 --xlevel filename.wav

is the recommended setting. Musepack is well supported on Windows PCs etc, but less so on Apple Macs at the moment. It's also fast to encode and decode, which is a real bonus on top of great quality.

As an aside, if you want wider compatibility with other computers (and hardware players), you might still consider MP3 encoded with lame 3.90.2 (or 3.90.3) at --alt-preset standard, which will be slower to encode, and create a large file, but will only rarely be noticeably worse quality than MusePack.

lame --alt-preset standard filename.wav filename.mp3

One further point - I did some restoration of a cassette-only music release recently and although I used Dolby B to get the correct treble timbre and reduce tape hiss, I still had audible hiss (at about -56 dB from full scale), especially on a quiet tune. After using Exact Audio Copy's WAV editor to Reduce Noise by 24 dB, the musical quality, to me, seemed just as high, with inaudible hiss (you have to be careful to watch out for quality degradation when doing digital noise reduction). On a moderately quiet intro passage about 13 seconds long (where the hiss was clearly audible, and thus being encoded), encoding the samples from "before" and "after" hiss reduction, the MPC bitrate dropped from 167 kbps with hiss to 135 kbps without it and the Lame APS dropped from 195 kbps to 165 kbps.

It is plausible that some of the intended audio got removed along with the hiss, but I tried to audtion my settings carefully and fairly loudly on headphones (even greatly amplifying a fade out to pick up the telltale signs of excessive digital NR).

I'm sending you a PM, Fiath, with a link explaining in detail how I did the audio restoration of that cassette. (I must also try Audacity's Noise Reduction routine one day)

Wow! Thanks for the tips!

As usual, it is more complicated than I thought. But I guess now we have no excuse but to produce top quality digitised tape recordings.

Really, *very* much appriciated!!

That's nice to hear.

Any chance you could forward me that PM as well. I've got some conversions I recently did with hiss, and would love to get that hiss out of there. Thanks for any help.

voltron

Sure, I've just forwarded it to you, Voltron. If anyone else wants details of the restoration, PM me directly and ask for 'details of the cassette restoration' rather than posting here.

DickD