Just in case someone missed it when there was some discussion in the past, a Windows ACM codec is available for Sony ATRAC3, also known as MDLP or MiniDisc Long Play. The codec includes support for encoding 66kbps, 105kbps, and 132kbps streams.

If you want to experiment, the codec is available at http://www.minidisc.org/atrac3.zip. This is the only reference ATRAC3 codec release I know of, other than the non-ACM ATRAC3 codec included in RealProducer and RealProducer Pro.

Even if you don't have access to any MiniDisc hardware, it's another standardized lossy codec you can experiment with. If anyone knows where to get an ATRAC (ATRAC1) codec, I'd appreciate it.

How doas that work with Sony having intellectual property rights on that audio compression standard?

Why would anyone release such a codec to the public?

Christian

Well, the same way it works with AAC and MP3, neither are open standards but still, the code does manage to live.

Small correction - both AAC and MP3 >are< open standars - everybody could get standard description from local ISO office.

What you probably mean is the patent stuff - these codecs are covered by many patents, but almost all codecs are, too (except Vorbis reference implementation)

Does Vorbis have _no_ patent issues at all? I keep hearing the odd rumour here or there that, purely by accident of course, it does break certain audio encoding patents (because some methods that are patented are trivial & necessary to almost all encoders?)

I know nothing about this... (so tell me to shut up if im talking out my arse) but what is the official word on this at present....(just out of my own interest)

Cheers,
-Nic

ps
Please ignore if this has been taken up elsewhere & i have just been too lazy to find it....

as far as i know the actrac3 codec that you have posted is not the same as the codec that is used on minidiscs

it's a codec from sony for secure internet music distribution, the names only sound equal
maybe parts of the minidisc codec are used, but they are not identical

i don't remember where i read this though

Old ATRAC (used in MiniDisc devices) is rather old coding standard, working on nearly 300 kbits/s. ATRAC3 is low bitrate codec, with lower quality than ATRAC.

I believe ATRAC3 is used in minidiscs, it's so called MDLP (Minidisc Long Play codec), like TrNSZ explained in his first message, and it's not very old.

Then there's ATRAC 3 (notice the space) which is a high bitrate but quite old codec. I'm not sure what's the latest high bitrate Atrac version, but there exists at least ATRAC 7.

So the naming is very confusing...

[edit]
ah, Ivan above was quicker than me.

The ATRAC3 codec posted above is the same used in MiniDisc MD-LP mode. Plain ATRAC, also called ATRAC1, was the older high-bitrate, high-quality codec, which was used on all standard MiniDisc players before MD-LP support was announced. ATRAC has gone through various revisions and modifications and the naming convension can be confusing.

ATRAC3/MDLP is a 131kbps codec and was designed to compete with the "128kbps MP3 market" in the MiniDisc world.

I noticed there's up to ATRAC6 already. Any of these available as standalone software codecs? I also saw the ATRAC3 ACM codec is basically an unofficial version not made by Sony. Who are the people responsible for this codec though and where would they release new versions? (the codec didn't just come out of nothing did it..)

Sony used to have some player available that they would use to distribute ATRAC3 encoded content, and this codec was derived from that.

The "ATRAC 6" codec you speak of isn't ATRAC6, it's ATRAC 6, which is revision 6 of ATRAC-1. Same thing with Type-R ATRAC. This is correct to my knowledge.

a real jukebox has ATRAC3 encoding option, with 132Kbps, so it matches one of the two Sony ATRAC3 recording rates. Does anyone know if this *is* Sony ATRAC3, or it just uses sony algorithm but the headers etc are not compatible?

If someone can create ATRAC3 track on PC, and then copy it from PC to MD player (I'm not sure if NetMD allows it), this will be almost as flexible as non-MD formats (that is, MP3, AAC, etc).

This is the standard ATRAC3 codec, however, it is wrapped in a RealAudio file, just as the ACM codec wraps the ATRAC3 output in a WAV file.

It's next to impossible to copy ATRAC/ATRAC3 audio to an MD, because there is the Audio/Data "firewall" that prevents this. For more information, you can check www.minidisc.org.

Currently, there seems to exist only one solution that allows transferring ATRAC files to a PC for decoding, or ATRAC files to MD, and it's cost is over $5,000USD.

Ah, so basically there are only 2 ATRAC codecs, ATRAC(-1) and ATRAC3 and the ATRAC 1-6 represent the revisions to ATRAC(-1). Have any revisions to ATRAC3 been made?

"Sony used to have some player available that they would use to distribute ATRAC3 encoded content, and this codec was derived from that."

I see, but who are the people responsible for this ACM codec?

Most likely, it originates from Sony Asia:

http://www.css.ap.sony.com/downloads/downl...000000000000017

Basically. =) There was ATRAC, ATRAC2, and ATRAC3, however I don't think ATRAC2 was ever used commercially in any consumer equipment.

There are papers describing ATRAC at http://www.minidisc.org/aes_atrac.html, ATRAC2 at http://www.minidisc.org/atrac2_paper/1.html, and ATRAC3 at http://www.minidisc.org/atrac3_article.pdf.

To my knowledge, there has only been one implementation of ATRAC3 released, and about ten different implementations of the ~300kbps ATRAC codec.

Well yeah, but that's just the decoder. Is the ATRAC3 encoder a hack of the ACM codec provided by Sony?

10? You mean there were other revisions besides the 6 you already mentioned?

Damn, this is confusing.

Wish I could answer that one.


Well, lets see, Sony ATRAC 1, 2, 3, 3.5, 4, 4.5, Sharp ATRAC 5 and 6, Sony Type-R. That's nine different types, and there was a "bugfixed" version of ATRAC 3 that fixed a stereo phase bug that I know of as well. I hope I'm correct on all this, it's all from memory.

As far as ATRAC3, I think all ATRAC3 codecs are identical.

Yeah, there also seems to be a bit indistinct whether there is Sharp Atrac v7, but it seems that the mix up was born when Sharp talked about seventh generation Atrac..(?)

Right so there are at least ten different versions of the ATRAC codec. This isn't suprising, really. How many different MP3 encoders (and versions of those encoders) have been released? It's still all MP3. The same goes for all these different ATRAC codecs and revisions.

You can seriously tell a quality increase from the original ATRAC codec in the first MD equipment when comparing to modern (Sony 3.5 or higher, or Type-R) versions of the codec.

Thanks for the answers, TrN. If you (or anyone else) is up for a comparison, can you do a listening test between the following samples:

[removed]

They're compressed WAVs by the way - you'll need to have the ATRAC3 ACM codec installed to do proper testing. Please tell me which sounds best to you, I'll give the answers sometime later.

Did a blind listening test with a friend to help, here are the results:

Sample3 sounds really muffled and has terrible tone and maybe too agressive of a lowpass.

Sample2 sounds worse than Sample1, mainly because it seems to be missing high frequencies.

Sample1 sounds the best.

What are you trying to prove? :-)

Thanks a lot for the results!

It was a test to see which codec would be best (at this time) for use in AVIs (when bitrate should be low). Samples 1 and 3 were first resampled to 32 kHz with SSRC HP, then dynamically lowpassed at 14 kHz (with the same start-end values as Lame uses for 32 kHz) with GoldWave, using steepness 20. Sample 2 was lowpassed only (with the start-end values Lame uses for 44.1 kHz).

Sample 1 is Lame 3.89a7 with commandline --resample 32 -m j --abr 103 --nspsytune --ns-bass -8 --athtype 0 --athlower -2 -q 3 -t

Sample 2 is ATRAC3 105 kbps stereo (44.1 kHz - didn't accept 32 kHz input)

Sample 3 is the Radium hacked FhG Pro MP3 96 kbps, 32 kHz, stereo

Conclusion is clearly that Lame is best, but it's odd you found Sample 3 to use a too agressive lowpass, as all were lowpassed at the same value. Maybe FhG uses an internal lowpass at low bitrates below 14 kHz..

Personally, I found Sample 2 the worst - the castanets all sounded like they "rolled over" in each other. Was really horrible before I added the lowpass.

I was rather unimpressed with ATRAC3 at 66kbps and 103kbps, but the 132kbps mode was very decent, actually.

You think ATRAC3 at 132 kbps would beat MP3 at 128? Maybe we should do a new test between Lame and ATRAC3 at those bitrates. Can use a higher lowpass then too, so we can see which reproduces fidelity better.

It would be an interesting test. It's only fair to compare 132kbps ATRAC3 against 128kbps MPEG-1 Layer 3 CBR, in my opinion. ATRAC3 is a CBR only codec after all. Currently, ATRAC3 reserves extra bits and frame headers (which uses about 4kbps) for maintaing backwards compatbility with existing ATRAC implementations. By doing this, rather than crashing the decoder or outputting garbage or static, an ATRAC decoder will play an ATRAC3 audio file as silence.

It would be interesting to test a few samples and see what the outcome is. Most people have AC97/PC99 soundcards. I think the best way to do a real test is to highpass at 20Hz, lowpass at whatever LAME 3.90a7's default lowpass is for 128kbps, and then encode the samples (at 44.1kHz). Then, after encoding, decode the two samples back to uncompressed WAV format, and use ssrc to resample both samples to 48kHz, and then do the listening test. This should make everyone happy, and we don't need to worry about the Windows or soundcards hardware resampler.

Side Note: It would also be very interesting to use an ATRAC3 hardware encoder and see if there are differences against this ACM. Since I work at Best Buy, I may be able to use an MD-LP deck and encode the low- and high-passed samples, and then copy them to WAV files (via SPDIF).

What do you say?

Edit: I did a frequency chart of the three samples, because I was worried when you said that the FhG/Radium sample wasn't lowpassed any differently than the ATRAC3 sample. Even the terrible pre and post echo of the ATRAC3 codec was better than the lost highs in the FhG sample, to me. LAME went through past 19kHz, ATRAC3 cut off around 14.5kHz, and FhG/Radium started to cut off closer to 12kHz. Notice how the frequency response of the FhG/Radium clip is totally off, where ATRAC3 and LAME are very close to each other. No wonder the third sample sounded so bad! 12kHz through 15khz is gone, and the "tone" and general sound is completely different than the original. In the other graphic, you can see the pre-echo and post-echo. ATRAC is obviously worse than both the MP3 versions. It doesn't introduce excess clipping though; MP3 does.

[img]ad6327d44d[/img]
[img]ad6327d44d[/img]

You're right, it's better to compare ATRAC3 to MP3 CBR if it is only a CBR codec (I wasn't aware of this before). Alright, I made 3 test samples lowpassed at 15115 Hz - 15648 Hz (Lame's default lowpass width for 44.1 kHz) with GoldWave (using default steepness 5, I thought 20 was a bit too high, doesn't accurately represent Lame's lowpass I think).

fatboy.pac applaud.pac castanets.pac

Encoded to MP3 with Lame 3.90a7 --resample 44.1 -m j -b 128 --nspsytune --ns-bass -8 --athtype 2 -q 3 and decoded with Lame 3.90a7 --decode --decode-mp3delay 576 then resampled to 48 kHz with SSRC HP, no dithering:

fatboy-LAME-48khz.pac applaud-LAME-48khz.pac castanets-LAME-48khz.pac

Encoded to ATRAC3 132 kbps, stereo and resampled with SSRC HP, no dithering:

fatboy-ATRAC3-48khz.pac applaud-ATRAC3-48khz.pac castanets-ATRAC3-48khz.pac

Two notes, both pretty important I think:

1) I couldn't turn off Lame's default lowpass when encoding at 128 kbps (I didn't want to use -k because I'm not sure if this only disables the lowpass - it might disable other filters as well) so I used the original samples and used Lame's internal lowpass filter. This might give different results than using GoldWave's lowpass filter, so maybe new tests should be made for that.

2) I didn't specify -t upon encoding, so it might be that the VBR header (which is apparantly also added to CBR encodings) was tacked on the MP3 files. Lame should remove these from its own files upon decoding though, so there's probably no problem.

Also, I didn't add a highpass, because I don't know what Lame's default width for its highpass filter is (why did you want to use a highpass filter actually?)

It would be very nice if you could make encodings of the 3 already lowpassed samples to see how they stand up against the ACM codec (doesn't using the SPDIF output introduce jitter though?) It might very well be this codec doesn't accurately represent ATRAC3's real potency.

Btw, I didn't add results for the Radium codec this time, because I only have 4 kB free space on my provider's website now. So I'll have to remove the samples sometime later (previous 3 samples were already removed) and then I can add Radium samples (though you can of course also make the encodings yourself if you wish - just use the 3 samples at the top). If you could show me some graphs for those samples that would be great!

I made encodes with the Radium codec (128 kbps, 44.1 kHz, stereo [Joint stereo: MS]) and decoded them with lame --decode --decode-mp3delay 864 then resampled to 48 kHz with SSRC HP, no dithering:

fatboy-Radium-48khz.pac applaud-Radium-48khz.pac castanets-Radium-48khz.pac

These are up on my FTP - you can also get the rest of the samples there if you go to ftp://213.46.58.25:20001.

Edit: and 6 Ogg versions, all encoded at 128 kbps (note though that fatboy came out much larger, because Ogg is inherently VBR) and decoded with the Winamp plugin Nullsoft Vorbis Decoder 1.16 with dithering disabled, resampled to 48 kHz with SSRC HP, no dithering:

fatboy-OggRC2-48khz.pac applaud-OggRC2-48khz.pac castanets-OggRC2-48khz.pac

fatboy-Ogg07102001-48khz.pac applaud-Ogg07102001-48khz.pac castanets-Ogg07102001-48khz.pac

RC2 is from the latest official release and 07102001 is the latest daily binary (development snapshot).

What is the installation procedure for ACM codecs on Win2K/XP?