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[Matt_G]

UnderTow wrote on Sun, 16 July 2006 15:36

Jon Hodgson wrote on Mon, 10 July 2006 17:04 blue2blue wrote on Mon, 10 July 2006 16:10 And on the practical (though subjective) side, your final paragraph's proviso should give some reassurance to those who need to service multiple conflicting formats, ie, video at 96 kHz and conventional CD audio at 44.1 kHz. The most important thing is to get a good SRC. I was quite surprised when I saw this page http://src.infinitewave.ca/ Now I can't confirm the quality of their testing, but if they've done things correctly then it seems to tell us three things 1) It is possible to achieve extremely high quality (170dB is 28 bits worth) 2) Plugins and programs aimed specifically at mastering tend to have higher quality than your standard DAW SRC (different priority, in a multitrack DAW you are trying to keep processor use down so you can have as many tracks and plugins as possible, in a mastering program you can throw all your resources at just two tracks). 3) Even in the worst case in these tests the artifacts are only just edging up into audibility, so use those CPU draining SRCs when you're mastering, by all means, but don't lose sleep if you don't have one. Just a small comment here: I contributed the Sonar 5 entry. It isn't a realtime SRC. It only happens when you import or export files so processing load isn't part of the equation. It just isn't a very good SRC. No excuses. This has been mentioned to Cakewalk so they might do something about it in Sonar 6. Especially considering that they allready license stuff from Voxengo. (Like Pristine Space convolution reverb). Alistair

I participated heavily in getting a lot of the SRC results to Dave Horrocks who is hosting the SRC graphs http://src.infinitewave.ca/. I submitted the Barbabatch test files and quite a few others.

I also got to play with most of the SRC's on a piece of music I mastered to test the reuslts. Most of them were very close to being identical & doing some Null tests between the test files helped clarify that. I wish iZotope would release their SRC algorithm as a stand alone application for Mac. It really was outstanding.

Matt

[maxdimario]

if your master file is 88.2 and you bring it to be mastered on a 44.1 cd, doesn't it make more sense?

isn't it a question of ommitting every other sample?

what other processes are involved in taking a recorded 88.2 and converting it to 44.1?

[Jon Hodgson]

maxdimario wrote on Tue, 18 July 2006 10:58

if your master file is 88.2 and you bring it to be mastered on a 44.1 cd, doesn't it make more sense? isn't it a question of ommitting every other sample? what other processes are involved in taking a recorded 88.2 and converting it to 44.1?

You first filter out everything above 22kHz

Then take every other sample.

If you were going from 96kHz to 44.1kHz then the process starts the same, you filter out everything over 22kHz

But then it gets more complicated, because you then need to sample at points in between the original samples. So in effect you have to upsample then downsample.

I say "in effect" because a common approach is to use polyphase filters which combine the three stages in one. Mathematically it's identical to doing the three stages seperately, but it's a performance optimization.

Using a polyphase to achieve the same quality of result from 96kHz to 44.1kHz as from 88.2 to 44.1 will require more memory for coefficients.

[ericjenson]

i always upsample to at least 96k if not 192k
and 32-bit float

because the EQ plugins i use sound much more accurate and tighter in the whole spectrum, e.g. PEQ Orange, PLPAR EQ. but especially bass, if i want bass control with an EQ i have to upsample to 192k for the control i need in this region of the audio, no question about it.

also if i'm using any tube emulation or tape emulation, essentially anything nonlinear, it comes back sounding much better and with the intended effects, even after downsample, i don't know for sure, but i would guess it's because since there are more samples for the plugins to shape the way they do, it sounds smoother in the end.

even the compression plugs sound better and smoother in my own experience with it.

i'm using secret rabbit code, btw, for my conversions.
and sometimes Audacity, which uses the same sinc interpolation that secret rabbit code does.

so the SRC and the quality of it may also play a large factor with all of this.

but even before when i was using r8brain pro, still much better sounds with an upsample at the beginning of the process.

and to go further, it still sounded better to me way back when i was using wavelabs built in src plug, which tested poorly against the others.

[ericjenson]

Quote:

The most important thing is to get a good SRC. I was quite surprised when I saw this page http://src.infinitewave.ca/

i think secret rabbit code at 64 bits should be included in this test