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2. Basics
The sampling frequency is basically the number of times per second audio is sampled and stored as a number - CD audio is sampled at 44.1 KHz, which means 44,100 samples per second. CD audio uses 16 bit samples, so the bitrate of uncompressed CD audio = 44,100 x 16 bits per second (well x 2 actually, because it's stereo). The "bitrate" on the other hand, when talking about MP3 files, refers to the transfer bitrate for which the files are encoded - i.e. an MP3 file encoded "at a bitrate of 128 kbps" is compressed such that it could be streamed continuously through a link providing a transfer rate of 128 thousand bits per second but most of us don't really use MP3 as a streaming medium (except for Shoutcast, etc.) so really what the MP3 "bitrate" is a measure of is how severely the files is being compressed. The lower the bitrate, the more the file has been compressed and the more you compress a file, the more of the original data is lost, and so the worse the playback sound quality will be. It's almost exactly analogous to compressing a JPG image with a higher compression ratio - you get a smaller file, but when you view it, it doesn't look as good. PLEASE NOTE: The feedback comments below are considerably beyond the knowledge of those editing/revising FAQs but are left for the information they contain. However they would be far better in one of our forums where their exposure would be greater and others could contribute or learn from them. NOTE2: The following information was left in a comment, but was removed due to language and attitude. Cleaned up and edited, here it is: No, the author does not mean bit "depth", which is what you're describing. He means said bit rate and means bit rate, (one is time-based, one is, well depth-based, so it is a one-dimensional value with an arbitrary unit). And I'm sorry, but what you're saying about reverb is [incorrect] ... Most all reverb is a DELAY-based effect, except when you're talking about convolution reverb, and regardless, in either case it has [nothing] to do with oversampling because oversampling techniques are only ever employed to improve a signal's quality (because that's what they do in audio). And sampling, which concerns quantization in the TIME axis of the wave (i.e. "x") .... Again, reverb is delay-based, and if any errors exist in the audible spectrum, the reverb will process them and you will hear it. Changing the bit depth, which again is the quantization in the y-axis (so basically the resolution or number of bits or or range the amplitude of the wave can occupy (16 bit, there are 2^16 values, so 65,536 values, 24 bit, 2^24 values and so on, same as how a sampling rate of 44.1 kHz allows a resolution of 44,100 in one second in the x-axis of the wave)) will not change [anything] in the time domain.And saying those other effect's quality depends on the bit depth is incorrect, as is your comment about bitrate, which you describe incorrectly. The author was right in his definition. Feedback received on this FAQ entry:
by snapcase$ A file with the .VIV extension or a VIVO file is a proprietary video format from Microsoft. To play a video in .VIV, simply use Windows Media Player or VLC Player. by snapcase$ Unfortunately, yes. Well, in a sense. You MAY get a virus through a hole in your email client or by opening/executing an attachment, just like you MAY get a virus through an MP3 player with a hole in it or perhaps by clicking on a file you THOUGHT was an MP3. Computer literacy and due diligence is required. Keep your MP3 player (and email client) up-to-date to prevent things like this. Various forms of malware can be hidden in a supposed MP3 file, including worms, viruses, and trojan horses. The numerous person-to-person file sharers are breeding grounds for these undesirables so it's rather important to know and become familiar with the warning signs: •Distorted File Names •Unusual File Sizes •Multiple or strange file extensions (.exe) A strong and frequently updated anti-virus program may be considered by some an absolute necessity these days. A good free one can be found by checking our security or software forums. For additional information, visit the Security Forum. by snapcase$ Not a good idea. You can run your own FTP server to share your MP3 library but there are a number of issues that must be addressed beforehand such as copyright violations, the big one: »acomp.stanford.edu/info/dmca/ Make sure to check with your ISP before you go ahead and operate your own FTP server. Running servers is often a violation of your ToS (Terms of Service) and can result in them disabling your account. Many providers have now instituted CAPS which would also be a major concern. Alternatively, you could always pay for FTP hosting on a commercial server but the sanctions against this now would most likely make it unwise. by snapcase$ A skin is used to change the look of your MP3/media player. Some skin utilities are here. Most skins for a particular player can be found at the developer's website. by snapcase$ A plug-in is an extra add-on that offers optional features such as visualizations, output enhancements, effects, etc. A few plug-in utilities can be found here similar to skins. Most plug-ins for a specific player can be found at the developer's website. by snapcase$ VBR stands for Variable Bit Rate. It's a method of encoding audio to MP3 that allows for different sections of the file to be encoded at different bitrates, depending upon the demands of the source audio (some type of sounds require a higher bitrate, others encode well using a lower bitrate). Edit: Updated info ... the good LAME MP3 encoders(version 3.90.3, I think) can control the size of the VBR MP3. --alt-preset standard is the default VBR mode with around an average bitrate of 205-240k per song, --alt-preset standard -Y will make it around an average bitrate of 170k-200k. [These presets and LAME settings were developed at hydrogenaudio.org]VBR is quite flexible with LAME, and it doesn't have to be a bloated filesize to give better quality. Usually the encoders that had those bad artifacts with VBR were xing and blade, but good encoders do VBR very well. ------ Thanks to Thasp  for this updated info.The advantage is that VBR encoded MP3s are generally smaller than standard MP3s of the same sound quality and generally sound better, especially in the high frequencies. by snapcase$ LAME is a high quality MPEG Audio Layer III (MP3) encoder licensed under the LGPL. Latest LAME release: v3.99 (October 2011) LAME is considered the best MP3 encoder at mid-high bitrates and at VBR, mostly thanks to the dedicated work of its developers and the open source licensing model that allowed the project to tap into engineering resources from all around the world. Both quality and speed improvements are still happening, probably making LAME the only MP3 encoder still being actively developed. More about LAME by KeysCapt | ||||
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