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WEB-READY MEDIA FILES
Introduction
Using media files on the web doesn't mean just uploading a file (audio, video, flash) and offering a link to click for a download. You can do that with any kind of file, space and bandwidth permitting, and you'd then only be using your web space as storage.
I will concentrate on audio files here, since I have more material for them and they are easier to handle, requiring less specialized proprietary software (read: not free) than video or flash.
I am not an expert in the technical aspects of audio manipulation (such as recording and editing), but I am fairly comfortable using a variety of formats and can offer guidance to what's good to use in web applications in particular.
Most of what I am about to explain here may only apply to a Windows environment, not MAC or Unix, except in very general terms. However the software I will describe usually only works on a Windows PC.
In coming days and weeks I will add more information to this tutorial, and provide more structure to it.
Types of Audio Files
An audio file in its purest uncompressed form is a wave file (file extension .wav). In particular a .wav file described as 16-bit PCM uncompressed 44.1KHz 2-channel stereo is equivalent to the contents of an audio track from an audio cd. It is also what most soundcards output.
Such an uncompressed wav file occupies approximately 10MB of space per minute of audio. So a typical 3 minute song will be 30MB, much too big a file for using on the web, especially if all 30MB have to be downloaded and played in 3 minutes. Clearly that's not a good format to use on the web, even for high-speed internet users.
Most everybody is familiar with the mp3 format and others like flac. In addition to these we have wma (Windows Media) , ra and rm (Real Audio and Real Media), m4a (Quicktime audio) and a bunch of other formats.
Compressed audio formats are of 2 kinds: lossy and lossless. For lossy formats this means some audio quality is lost during compressions. Once you compress your original uncompressed wav to that format, you will not get back the same exact quality wav file by reversing the process. The lossless formats allow conversion back to the uncompressed wav with no loss whatsoever.
The mp3, m4a and Real formats are lossy. The wma format may be lossy or lossless. Flac may be lossless. Lossless formats cannot be compressed much more than about 50%. Lossy formats allow compressions to some amazing levels however.
Lossless compression is somewhat similar to using winzip to compress some files. When you unzip you get back the same exact original files you started out with. The lossless wma format is supported by Windows Media Player series 10 and higher and offers about 50% compression. Some of the more modern portable players (known as mp3 players at times) support lossless wma as well. Flac is favored by many as a lossless format, but it is less widely supported.
Lossy compression works by changing the bitrate of the audio file to a value much lower than that corresponding to the uncompressed wav (which is about 1100kbps). If you are familiar with mp3 files you will recall bitrates in the order of say 32kbps up to a maximum of 320kbps. The lower the bitrate used, the smaller the resulting compressed file and the lower the audio quality, thus "lossiness".
How lossy a lossy format is is a matter perception and taste. The more compressed the file is the worse it sounds. However it is debatable whether the human year can detect the lossiness in an audio file encoded at a 320kbs bitrate. In fact even at 192kbps it will be very hard to notice. A bitrate of 192kbps is considered to be CD quality, whereas 128kbps is near-cd quality, for mp3 files.
There are a multitude of programs available for performing audio file conversions. Some are free, some are not, just as some are good and some are not.
Some audio converters only perform conversions between certain formats. Some are more flexible and either have built in decoding and encoding codecs for a multitude of formats or allow you to install new codecs as needed.
A decoding codec "understands" and converts a particular format into a standard pcm wav. An encoding codec does the opposite. Conversion from one type to another involves using one or the other kind of codec or both, as needed.
One program that is freely available and which I strongly recommend is dBpowerAMP Music Converter, and the whole gamut of decoding and encoding codecs is available from Codec Central , in order to mix and match as needed. The only caveat is that the use of the mp3 encoding codec is subject to a modest registration fee, as it is required by patent legislation from all audio conversion programs. The debate as to whether that's fair or not is not relevant at this point. Nor is the remark that there may still be audio conversion programs which provide encoding to mp3 for free. Their legality and thus their reliability and longevity may be debatable.
I will not engage in any lengthy explanations of how to perform audio conversions using dBpowerAMP. All that is amply covered in their help files as well as the dBpowerAMP support forum.
Armed with dBpowerAMP Music Converter, dMC for short, you can take care of all your audio conversion needs including capturing and recording audio from cassette players and vinyl records or radio or other audio sources (e.g. games). Once you have an audio file on your pc, you can encode it to whatever you need for whatever application you need, including web applications.
Web-Ready Audio in A Nutshell
The most common audio formats on the web are: mp3, wma, ra and compressed wav. All lossy by necessity since all lossless formats result in files that are still too large for the web.
Bitrates that are suitable for web applications are 128kbps to 192kbps for ultra high-speed internet connections, 64kbps to 96kbps for regular high-speed connections and 20kbps to 48kbps for dial-up connections. As said before, the lower the bitrate, the lower the audio quality, but that's the tradeoff of speed vs quality.
The mp3 and wma formats are stated in terms of bits, bitrate, frequency and channels. The Real Audio format (.ra, .rm) are stated in terms of audiences. The compressed PCM wav is somewhat touchy. Its use should be limited to applications that require a wav, when you need compression, such as in some Flash audio applications or PowerPoint presentations (not really a web application in fact). Trial and error unfortunately best describes the choice of specs to be used for compressed wav.
The choice of mp3 or wma can be based on this simple rule of thumb: for hi-fi audio, at 128kbps and higher, mp3 is a very good format. It is however only recommended for ultra-high speed internet connections. At lower bitrates, wma offers better quality than mp3 down to the lowest bitrate possible. It can be said that a wma at bitrates from 20kbps to 48kbps is roughly equivalent in quality to an mp3 double that bitrate (thus double the file size).
The mp3, wma and compressed wav formats will be playable through the default player (usually Windows Media Player) when embedded in a web page. Real Audio will be played through real Player or Real One by default, or Media Player Classic if Real Alternative is installed. The latter however is limited in its capability of playing the increasing variety of Real audio file types, and in particular in its ability to stream audio through various appropriate meta files.
For web applications streaming audio is practically a must. This is covered in some detail in my Media Streaming Tutorial. Audio file conversions go hand in hand with the need for streaming.
A special type of audio file you will encounter on the web quite often is a MIDI file (file extension .mid). That is not actually an audio file, it is essentially a set of instructions to be used by a program to enable a synthesizer to produce sound according to a soundbank. Midi files are created by musicians using midi keyboards or computer programs that simulate keyboards and other instruments. The audio quality of a midi file depends entirely on the quality of the soundbank available and can range from horrible to awesome.
MIDI files are very tiny, yet with a good soundbank, the result can be stunning. Because they are not actually audio files, they cannot be converted to other audio formats - they have to be recorded to an audio format like wav first,, while being played through the computer's soundcard . You can use a midi file on the web but you must be aware that how it sounds depends on the end user's computer. But a midi file is the only medium where a 50k file can sounds as good as an uncompressed wav recording of a symphony ... or near enough.
Because midi is not an audio file as such, it follows that you cannot convert audio files to midi either. There are a few programs that attempt to approximate such a conversion, but the results are so poor, they are simply not worth mentioning as a solution.