Need Help With Audio Terms by neo_chip at 10:29 PM EST on November 25, 2011
Can someone explain briefly what are the terms used for stating the sample rate and what it means. I want to contribute some streams but I want to upload properly and know this stuff. I know some terms but I want to be sure what they mean :)
Thanks bxaimc how can you tell for example: when you look at audio sources you claim its a Nintendo DSP, is it because anything thats 32khz is automatically referred to as DSP?
Also compression Methods can you explain a little what that means cause I though ADPCM meant anything thats 48khz (aka lossless DAT).
No, as bxaimc said, DSP is the format. Are files automatically considered MP3 because they're 128 bitrate? Are videos automatically considered MPEG because they're 640x480 resolution? It's the same thing here. DSP is the format. There's 48khz DSP files out there (they're *very* rare...), as well as 32khz, and 22khz, etc. ADX, XMA, DSP, WAV, MP3, OGG, etc. are all different types of formats, and they can all be any sample rate that they're encoded in. So, what determines if something is MP3, OGG, ADX, DSP, etc.? That, I think, is the question you're intending to ask. The "determining factor" of a format, is what method (and how) the data within the file is arrange. Often (though not always) the "header" of the file will inform you what format the data is. Sometimes, there is no header though, so you have to recognize the file format by other means. Usually the file extension is used, if there's no header. However, sometimes even the file extension doesn't exist. In which case, you need to be able to view the file in a HEX editor, and recognize patterns of different formats.
So, in summary, a developer usually recognizes the format using the file header > file extension > data patterns (in that order, depending on what's available). The end-user never goes that "deep" into it, which is why I said "a developer". The end-user uses tools created by developers to recognize the different formats. VGMstream is one such tool (and, most likely, VGMstream uses the above mentioned to recognize file formats).
Regarding the compression - I'm significantly less capable of explaining this than I am at explaining formats (as seen above. Perhaps I wasn't very good at that either). Something can be "lossless" and be 11khz, depending on the original source material. And technically, anything recorded is "lossy", when compared to the original (since something will be lost in recording it...). Obviously, that's going a bit extreme, and that's not what you're question was. But your idea that 48khz is lossless is completely incorrect on all grounds. Basically, as I understand it, ADPCM is intended to mean ADvanced PCM, and is a form of compression (essentially a completely different form than MP3, just FYI). I'm going to stop now, because anything else I say will only muddle the topic, cause confusion, or be completely wrong altogether.
Hopefully my explanation on formats was at least a little useful.... Mouser X over and out.
I see, well how does an end-user like me can contribute source rips here? For example I ripped an xbox game recently and it contains .wma source. How Would I go by labeling the folder properly? I understand whats left of the question mark what do I put for compression method its in 44.1khz encoded in 128cbr?
PocketBike Racers (2006)(King Games)[Xbox][MS Windows Media Audio][WMA]?
Although I think Pocketbike Racers has more than just WMA in it. There's some Xbox IMA somewhere like in Big Bumpin'
by nothingtosay at 5:46 AM EST on December 2, 2011
You asked what exactly sampling rate means, so I'll boil it down for you and I think you should be able to get it without this being tl;dr. It is the number of times per second that the sound wave is digitized, or sampled. Standard audio CD quality is 44.1 kHz, Hertz being the unit of measurement for the frequency of something in times per second, so this means there are 44,100 0s and 1s of data per second, per channel, of audio.
The significance of this is that the sampling rate dictates the highest sound frequency that can be captured and reconstructed from the recorded data. I know we're using the term 'frequency' for two different things in the same subject, sorry but it can't be helped. To be clear, in this second case I'm referring to the sound's pitch, which is called frequency because the pitch is dictated by the number of peaks and troughs in the sound wave per second. The highest pitch that can be represented in digital audio is the same as the audio's sampling rate divided by 2. Meaning a 44.1 kHz file's highest possible sound frequency is 22.05 kHz. One at 48 kHz would have a limit of 24 kHz, and so on. This is called the Nyquist Frequency, after the guy who formulated the theorem.
44.1 kHz is the standard mainly because it worked well with the earliest digital recording equipment but also because it covers the entire range of human hearing even in the most ideal of circumstances. 48 kHz is the standard used in broadcasting. 32 kHz is often used in video games because it's less data to store/compute. Most adults can't hear pitch frequencies above 16 kHz anyway so a 32 kHz sampling rate can sound just as good as 44.1 to the majority of people. When you get down to the 22 kHz sampling rate things start to sound very unnatural because the Nyquist Frequency is only 11 kHz and it's cutting out frequencies that we do hear. Stuff like Banjo Kazooie and Mario Kart 64 used rates in this range, but unfortunately, even modern games use 22 kHz sometimes. I think bxaimc told me the God of War games do. These aren't the only sample rates, really they can be anything - PC88 games used something around 55 kHz, XA audio like on Playstation games used 37.8, "hi-fi" audio often uses 88.2, 96, 176.4, or 192 kHz, you'll notice all multiples of the two standard rates, because some people believe higher rates increase sound quality, and it's not uncommon for a DS game to use under 20 kHz for streams.
That's pretty much it. Hope I answered your question and was articulate enough not to make it confusing. Of course, the sampling rate doesn't matter here, whatever is in the game is what goes on the tracker.