Lossless stems
Comments
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After years of multiple complex & difficult-to-explain issues with NI stems, I really thought the new update would finally put it all to rest! No ALAC stem creation - okay, not too surprising, but surely an easy fix… But even Traktor Pro 4 still can't play ALAC stems on Windows?! 😓
Next, I'm almost afraid to ask - does TP4 on Windows produce extremely low quality lossy stem files on like Stem Creator on Windows did? If I recall correctly the Windows version of Stem Creator used an experimental encoder that rendered audio sounding like 32kbps MP3s. Hence the need to make lossless stem files in Stem Creator, which then Traktor would be unable to play if they had been made on Windows version of Stem Creator. An perplexing cycle of pain and incredulity. Maybe I should hold off on my license upgrade
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Just give the demo a try.
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No… literally "lossless" is in the MPG4-AAC spec. Although it does get a bit confusing as it does do lossy AND lossless. It's all about how you set it up.
Which again has me wonder whether ALAC was established to avoid this confusion.
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Hi everyone,
So if I understood well @Nico_Tf your tried this:
- Get your stems with another software (such as NUO)
- Go into Traktor and analyzed it to create the stems files also and the folder
- Copy the stems files from NUO into the stems folder created by Traktor (with the same name so it should erase the traktor's ones)
Did it work?
I also would like to import my own stems from my DAW (I'm a producer too) to have the best quality for my stems as I explained here:
Hi Alex btw!
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I don't remember arguing against this — I think you quoted the wrong person here. But still, I'm curious: can you link to your source please? The only thing I found about this is:
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You can use Stemgen to export a stem file directly from Ableton:
But it's not user friendly and you need to know your way around the terminal and have some basic Python knowledge…1 -
Hi @Wades ! Yes, this is exactly what I did. I used Cog to play the T4 generated stems in the Traktor folder, so as to locate the one I wanted. Then it’s indeed as simple as copying the filename, replacing the T4 stem with the NUO generated one, and renaming it by pasting the file name.
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I think the warbly and early 00s sounding aac encoder included in the original stem creator has traumatized anyone who used it, but the new stems sound very good. I don't think lossless will make them better, because every stem separation algorithm is VERY LOSSY by definition.
If you make your own stems for your own productions and render them one at a time, alac would make a world of difference.But complete tracks that get stuff artificially subtracted from them and are then glued back together on the fly are much different. Take a pristine quality flac/wav file of your choice, separate it with the algorithm of your choice and have it render wav stems, mix the stems back together. Then invert the stem mix and mix it with the original track. You're going to be surprised by the VERY loud artifacts that you're going to hear in this "delta" mix. This is what you are probably perceiving as mud when playing back the stem version of this track. I have tested every demucs mode as well as RX 9 and 10 with this method on lots of tracks, from modern squashed beatport tracks to very dynamic 70s and 80s prog rock songs, and all I got everytime was artifacts, lots of artifacts from the separation. Also, depending on the mix of the original track, stem track playback always sounds like you've put some transient shaper plugin on the master and you've set it at 0 but not precisely 0, just close to 0, even when the stems are lossless.
So maybe ALAC isn't what you're really missing, after all you do get your track (unevenly) spread across 1000kbps of information using the aac stems2 -
You’re right @Saradis, but.
The tons of artifacts generated by the stem splitting process is further aggravated by the re-encoding of them in a lossy format.
There’s something more insidious with NI stems: They have a compressor and a limiter on them by default. You can see that in Stemgen, and NUO allows you to turn this processing completely off in the advanced prefs (Put in ‘False’ instead of ‘True’ in the limiter and compressor on field). This may be what you hear when you talk of a transient shaper.
At the end of the day, preserving audio quality is always achieved by turning off as much processing as possible.
Hence, the best quality stems will necessarily be lossless, limiter and compressor off. It’s straightforward to compare the sound of a Traktor generated stem and a lossless/no processing NUO one, and to me the difference is night and day.
T4 stems are good enough for most uses. Being able to switch easily from the original to a stem is what was hampering stem use for me previously.
Only thing I’m asking now is to be able to use my own stems in the same way, and this probably could be achieved by simply adding a “Link external stem” in the menu and popping a file selector, nothing else needs to be changed, as evidenced by the switch-file-and-rename trick I pointed out previously.0 -
There's an M4L Device that uses DEMUCS to split an audio file into 4 Stems, then exports it to a folder containing the stems.
GitHub - diracdeltas/demucs4max: Demucs as a max4live device
I wonder if this could be modified to use the Stemgen stuff to also export a Stems file to the same folder?
Now, that would be MASSIVE step forwards for me…0 -
You’re not being optimistic Saradis. Source separation algorithms are only gonna get better: check out what AudioShake is doing. And of course producers and remixers make their own stem files. Check out what François K is doing! Well, I don’t even know why I’m still arguing about this…
Nico, the compressor and limiter are disabled in Stemgen. I don’t recommend using them so the only way to enable them is to change a JSON file.
And yes Patch, it’s doable. Both repositories are open-source so you can have a try!1 -
I do not understand one thing. If NI made STEMs generated in TP4 not-compatible with TP3…. They could expand STEM file format to be able to use flac. So, the problem that Traktor on Win cannot play STEMs with ALAC would be "solved". Flac could be used for loosless instead.
It may be valid argument that STEMs generated by splitting track are anyway so, so that loosless is not needed…. But one may generate STEMs also different ways…. And I wonder why Maschine does not have export of track also in STEM format…..
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My bad Alex! I meant the compressor and limiter are enabled by default in T4 stems (I guess, only way we’ll truly know is if NI confirm that’s the case) and also in the StemCreator app by NI, which a brainfart made me call Stemgen. Sorry for that!
Indeed, we agree that one shouldn’t use compressor and limiter on splitted stems.I could somewhat see the use if you are making a stem file of your own music with your own original parts, but else I think it’s mostly a bad idea to turn them on.
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@axeldelafosse I was definitely not arguing what @Nico_Tf wants which is a very fair ask, I was just saying that even lossless stems have audible garbage in them. And I know what an extra limiter sounds like. BTW I think that in TP4 the mixdown is handled differently because they sound much less muffled. But no matter how perfect the algorithms get, you can never have 4 files that contain more information than the original, all separated stems have very audible hollow points depending on what else is in the original file as well as how brutally the original is compressed. So, it's not a matter of optimism, we are probably at 90% or more of what future separations will sound like, we are constrained by the nature of sound.
I did the delta test with wav sources and wav stems output, and did the mixdown in audition which has sample-by-sample precision so you can invert the mixdown precisely on the starting sample, not playing back summed up stems through traktor so there was no limiting or any other effect used, and what was left (depending on source dynamics, genre and algorithm of choice) were very audible artifacts that are not in the original but are created during the separation so the stems sound more "convincing" on their own.
I was just stating that separation alone degrades sound quality, not arguing with anybody.3 -
Hey @saradis! I guess it figures that when you add back all the AI splitted stems you don’t get exactly the original file, as there is heavy processing done on each stem to generate it. That’s why it is better to play the original and only switch to the splitted version when you need it.
As for future advances, I tend to agree more with Alex. I just checked Audioshake as he advised, generated an acapella, and I was fairly impressed. But it does copyright detection, so useless for us, and that’s 16$ for an acapella anyway, so no thank you 😂
In any case, future will tell how far we can go.
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