Audiophile Series: E1 - Audio Files
If you are new to purchasing or downloading
music, first of all, you
will be puzzled by the file size, how a same song can vary from 3 MB to 100 MB?
Then I say what you will do, you will dive in the specs of audio and see some terms
like bitrate, channels, sampling rate, bit depth etc. and now you are really
confused. And at the same time you’ll be whining which one is better. Well,
have a read and you’ll be okay.
When you try to download music from torrents, if you dive in
the audio quality description, you will see there is something called bit depth
and it’s usually 16 bit or 24 bit. The promise is simple – superior listening
quality thanks to more data, aka bit-depth. That’s 24-bits of digital ones and
zeroes versus the puny 16-bit hangover from the CD era. Of course, you’ll have
to pay extra for these higher quality products and services, but more bits are
surely better right?
Bit-depth is all about noise, and the
more bits of data you have to store audio: the less quantization noise will be
introduced into your recording. By the same token,
you’ll also be able to capture smaller signals more accurately, helping to
drive the digital noise floor below the recording or listening environment.
That’s all we need bit-depth to do. There’s no benefit using huge bit-depths
for audio masters.
Surprisingly,
12-bits is probably enough for a decent sounding music master and to cater to
the dynamic range of most listening environments. However, digital audio
transports more than just music, and examples like speech or environmental
recordings for TV can make use of a wider dynamic range than most music does.
Plus a little headroom for separation between loud and quiet never hurt anyone.
The type
of compression used to shrink down the file size of your music library or
stream has a much more noticeable impact on sound quality than whether it’s a
16 or 24-bit file.
Sample Rate:
Sample rate is the
number of samples of audio carried per second, measured in Hz or kHz (one kHz
being 1000 Hz). For example, 44100 samples per second can be expressed as either
44100 Hz, or 44.1 kHz.
Bandwidth is the
difference between the highest and lowest frequencies carried in an audio
stream. The sample rate determines the maximum audio frequency that can be
reproduced. Theoretically the maximum frequency that can be represented is half
the sample rate (known as the Nyquist frequency). In practice, the limit
is a little lower, so the practical upper frequency limit for a sample rate of
44100 Hz, is a little over 20000 Hz, but less than 22050 Hz. MP3 format has sampling rate of 44.1 kHz, WAV
and FLAC formats have 44.1 – 192 kHz and DSD formats have 2.8-5.6 MHz.
What is kbps (Bitrate)?
We come along audio files with different kbps when we try to purchase or download. In a
vague sense, the larger kbps number, the better audio quality. We can calculate
this by following formula:
Bitrate = bitspersample(16-bit
or 24-bit)* samples/sec (44.1KHz-192 KHz for WAV)* no.of channels.
Example: 16-bit 48Khz strereo contains bitrate of 1.5Mb/sec.
Audio File Formats:
Audio files come in all types and
sizes. And while we may all be familiar with MP3, what about AAC, FLAC, OGG, or
WMA? Why do so many audio standards exist? Is there a best audio format?
It’s actually quite simple once you
realize that all audio formats fall into three major categories.
Uncompressed Lossless: WAV, AIFF etc.
WAV stands for Waveform Audio File Format. A lot of people
assume that all WAV files are uncompressed audio files, but that’s not exactly
true. WAV is actually a Windows container for different audio formats. This
means that a WAV file could potentially contain compressed audio, but it’s
rarely used for that.
The AIFF file is just a wrapper
for the PCM encoding, making it more suitable for use on Mac systems. However, Windows systems can usually open AIFF files
without any issues.
Compressed but Lossless: FLAC, ALAC etc.
FLAC stands for Free Lossless Audio Codec. What’s nice is that FLAC can compress an original
source file by up to 60 percent without losing a single bit of data. What’s
even nicer is that FLAC is an open-source and royalty-free audio file format,
so it doesn’t impose any intellectual property constraints. FLAC is supported by most major programs and
devices and is the main alternative to MP3 for music. With it, you
basically get the full quality of raw uncompressed audio at half the file size.
That’s why many see FLAC as the best audio format.
While ALAC is good, it’s
slightly less efficient than FLAC when it comes to compression. However,
Apple users don’t really have a choice between the two because iTunes and iOS both provide
native support for ALAC
and no support at all for FLAC.
Compressed and Lossy: MP3, AAC, OGG,
WMA etc.
These are smallest in size so best for storing in
portable devices sacrificing audio quality but its compression algorithm is so aggressive
that details are lost. Not the most preferable option for audiophiles.
If you’re capturing and editing raw audio, use an uncompressed format. If you’re listening to music and want faithful audio representation, use lossless audio compression. If you’re okay with “good enough” music quality, if your audio file doesn’t have any music, or if you need to conserve disk space, use lossy audio compression.
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