DIGITAL AUDIO ENCODING:

CREATING YOUR MUSIC LIBRARY

JAMES POOLE

MAY 2007

SummaryThis short report is primarily aimed at people who use the power of digital audio encoding to store and play their music. It explores different audio formats, looking specifically at the difference between lossy and lossless codecs. It finds that creating a music library out of lossy codecs isn't a particularly wise thing to do, due to the vulnerability of each format over time. Once obsolete, an lossy audio codec will leave the user with an imperfect music source. Instead, it recommends a different system, utilising the lossless codec system to generate a music library, and looks at a specific case where this is possible.

1 – An introduction

If you ask someone what file format they mainly use for their digital music, 9 times out of 10 the answer will be 'MP3' or 'AAC'. They fulfil the task these people require by allowing them to fit literally thousands of songs onto their portable music player. There are a horde of similar but less well known formats that will fulfil this task. Whichever one you choose, though, there is a common denominator – all of these formats are known as “lossy”, due to the way that they compress the music. When creating an MP3, you are essentially forfeiting musical information in order to reach smaller file sizes. This is good for some applications, as we will see below, but not so good for others. I am looking to make you aware of an alternative solution to creating your music library completely in MP3 – or any other lossy codec that you choose – and reasons why you should do this.

2 - Looking closer at MP3

Once again, I am looking at MP3, since this is the lossy codec that most people are familiar with, however what I say here will apply to most lossy codecs that you will come across.As a lossy codec, MP3 is great. It achieves astounding audio quality when you consider that it compresses music to about a tenth of its original size. However, by virtue of the lossy system, what you have on your Hard Disk Drive, or your MP3 player, is not exactly the music that you have on the CD or vinyl record that you obtained it from. The lossy audio system is irreversible; once you have created a lossy file, you can not get it back to being a perfect audio source. Although it achieves nearly CD quality, it can sometimes be noticeably different from CD quality music – especially at lower bitrates and with certain music genres. There are also other possible problems with MP3. Sure, everyone uses it now – it is ubiquitous within portable music players, and most media software on computers will play it with no problems at all. However, as a format, it is quite old. MP3 was created in 1991[1], an astounding 16 years ago! Remarkable in its day, MP3 music is now being challenged by rivals who say they can produce better quality lossy audio and have better compression rates. We cannot be sure that MP3 will be the format of the future. If we do find that it isn't, and you have created your music library in MP3 format, what have you got? A large job insofar that you will have to get out all your CDs again to re-rip them into the new popular audio format. Sure, you could just convert your MP3 library to the newer format, but there are weaknesses associated with this approach. Since you are working with a lossy format, you will be working from an imperfect source and will not be able to utilise the better quality of the newer format – in fact, the quality of your music can only be the same or get worse the more times that you convert it.

3 – A solution

If only there was a way of storing all your CDs on the computer in a form that is equivalent to actually having the CDs! Well, by now you have probably guessed (or already know – I'm not trying to be supremely patronising but I apologise if this is the case!), there is such a method, and the codecs that do this are originally described as “lossless”. In fact, you have probably come across lossless audio in the form of WAV files. Lossless encoding is the case where the quality of the produced file is equal to the quality of the source in the “same or less” inequality. Therefore, a lossless copy of a song on a computer will sound identical, through the same speaker system, as playing the song from the CD. This means that in the future, if you wished to have lossy formats

for portability, you can work once more from a perfect source. There are some downsides to lossless compression though, and is shown by their lower popularity in digital music history: the main reason is that they do take up more space, since it is not the primary aim of a lossless codec to compress the music. Certain formats, however, are able to compress the music while still retaining perfect audio fidelity. I'm not going to pretend that I am an expert on this, but there are many ways to prove this, as shown on many websites[2]. Their greater size makes them less 'portable' than their lossy counterparts. With portable music players probably being one of the main catalyst in digital music file proliferation, we can see how they are less popular.

4 – Why should I use lossless codecs for my music then?

The idea here isn't that you should use lossless codecs, its just another way of doing things. I personally prefer the idea of not having to re-rip the CDs again, and the greater music quality is always a bonus. The advent of cheaper digital storage affords us the possibility to 'splash out' on higher file sizes so we can have these benefits. It isn't hard to convert the lossless codecs to lossy codecs for your portable music player either. And if one day you decide that a different lossy codec is the way forward – Ogg Vorbis[3] for example – then the process is just as easy again. Instead of having to get all your CDs out again, and rip them one by one, you can just convert the music from your computer all in one go. Hook your computer up to a good set of speakers and what you effectively have is a music centre with your whole library available in CD quality!

5 – So are you suggesting a specific way of creating my music library?

Yes. Although no way is 'right', and we all have our own way of doing things, I believe that the method described in the diagram below is a perfectly valid way of doing things. It provides future-proofed CD quality music stored on your computer that is easily copied into the lossy form of your choice.The lossless compression codec that I have chosen here is one called FLAC, short for 'Free Lossless Audio Codec”. I have made this choice for a few reasons. FLAC:

● provides a relatively good compression ratio for a lossless format[3];● encodes reasonably quickly[3];● is free and open source (unlike MP3!!)[4];● has some hardware support in the form of portable music players, hi-fi systems

and more[5];● plays natively in many media players and also in ones that don't support it with

relatively easy to find plugins[6];● is increasingly being used as a medium of distribution amongst song artists[7].

There are certain considerations to make when going down the path that this idea describes to you though. My (very rough) calculations are that each day of music you have will encode into approximately 10GB of data in 'normal quality' FLAC form – although there is nothing to stop this being higher, up until the point where the compression ratio is 1 (i.e the 700MB of music on the CD will encode to 700MB in FLAC, ~12.6GB/day). While this is better than WAV, it is a large amount of data (especially when you consider that MP3 will, by the same calculations, encode to approximately 2.2GB/day), and will mean higher costs in the name of digital storage media. Also, FLAC is not universally supported, so it may mean you need to make some software, or even some hardware changes. These aside, I believe that this is a good course of action to take when putting your music onto your computer.

1. Get all “hardware music”

2. Use computer to convert to FLAC – save on HDD

3. Convert to requiredlossy format for portablemusic players when needed

4. FLAC format can be used for CD quality audio in Hi-Fi systems. Wireless connection to speakers?

I have used the 'FLAC frontend' program illustratively in this diagram. What I would in fact recommend you do to rip the music to your computer in FLAC format is to use a program called EAC along with the FLAC frontend – this is described in the link below.

6 - Conclusions● Lossy music compression provides good quality audio at impressive sizes and is

ideal for applications where portability is key, e.g in personal MP3 players;● Creating a music library primarily out of a lossy format is not the best idea, since

it is likely that the present lossy “format of choice” will change, leaving you with the task of re-ripping your CDs;

● Lossless audio codecs are an identical music source as CDs are, but are stored on your computer. Therefore they are the good choice for creating a music library, out of which you can convert copies of the songs to lossy formats for portable music compression.

Links and other interesting sites mildly relevant to this subject[1] - http://en.wikipedia.org/wiki/Mp3[2] - http://www.bobulous.org.uk/misc/audioFormats.html[3] - http://www.vorbis.com/[4] - http://flac.sourceforge.net/features.html [5] - http://flac.sourceforge.net/links.html#hardware[6] - http://flac.sourceforge.net/links.html#software[7] - http://flac.sourceforge.net/links.html#music

More Information http://flac.sourceforge.net – a look at FLAChttp://en.wikipedia.org/wiki/Mp3 – wiki's take on MP3http://en.wikipedia.org/wiki/FLAC – wiki's take on FLAChttp://www.bobulous.org.uk/misc/audioFormats.html – another explanation and comparison of lossy and lossless codecshttp://www.bobulous.org.uk/misc/audio_formats_comparison_2006.html – a newer version of above, with more explanationhttp://www.bobulous.org.uk/misc/openVclosed.html – explanation of open and closed source softwarehttp://reviews.cnet.com/4520-10163_7-6226087-1.html?tag=nav – converting your vinyl music to digital form

Softwarehttp://flac.sourceforge.net/download.html – get FLAC! http://www.exactaudiocopy.de/ - homepage for 'Exact Audio Copy (EAC)' software described above!http://wiki.hydrogenaudio.org/index.php?title=EAC_and_Flac – setting up EAC to rip CDs to the FLAC formathttp://www.winamp.com/ - media player that natively supports FLAC, though this is by no means the only one – look at the 'software' link at point [6] above