High resolution audio, a scam or a necessity?

Eleven months have quickly gone by and once again, we are in the festive season. Let me take this early opportunity to wish my readers a wonderful festive period. For tech enthusiasts like me, CES 2014 is only a few weeks away and I know you can’t wait to see what faster, thinner and more efficient ways tech companies have come up with to steal money from us.

I don’t know how many of you have heard of the term High Resolution Audio (HRA) but apparently, it’s the next big thing in the audio industry. The term High Resolution Audio refers to a new audio compression technology that seeks to provide better quality audio. Without going to the nitty-gritties, the tech seeks to improve the quality of sound from our digital music players by increasing the sampling rate and consequently the bit rate of audio signals from our digital audio players.

For you to better understand this, it’s good to have some background knowledge about the analog to digital conversion process. To put it simply, it’s the process of converting an analog signal into a digital signal. As we all know, audio is an analog signal and for it to be processed by digital devices, e.g. your smart phone, it needs to be presented in this manner (digital) to the phone.

The analog to digital conversion process works by sampling an analog signal at a constant rate, recording the value of the analog signal at each sampling instant and storing the number in binary form (you know the language of computers).

The binary information can then be stored on a storage device like a CD, DVD, and Flash Disk. The digital signal processing device, for example a phone must then be able to take the 1’s and 0’s presented to it and convert them back into the analog audio signal. This is achieved by the use of a DAC (digital to analog converter) which use encoding schemes like PCM (Pulse Code Modulation) to interpret the binary information into an accurate representation of the original analog audio signal.

The accuracy of the conversion from the DAC process depends majorly on the sampling rate of the analog audio signal. If a high sampling rate is used, the reproduced audio signal will almost be identical to the original signal. On the other hand, if the sampling rate is low, the reproduction won’t be as accurate. On the other hand, the higher the sampling rate, the more the number of bits required for the digitized audio signal and thus the bigger the space it will take.

So as to save on bandwidth and storage space, a compromise has to be reached between quality and size. MP3 compression has managed to provide this balance for quite some time now. CD audio quality provides better sound but with bigger audio files. Nevertheless, MP3 audio quality has proved to be quite adequate for daily usage thus its popularity to date.

MP3 audio compression is lossy which means that part of the information is lost during the compression process. This is what leads to its reduced size and relatively poor quality. Well poor is used sparingly in this case.

So why do we compress audio in the first place?

Well an audio signal is basically an analog signal. In order to store an analog signal, theoretically, we would require infinite bandwidth. Therefore, the compression process takes the analog audio signal, digitizes it and compresses it to save on storage space. The compression process itself involves the use of algorithms that for example, can represent 40 bits with about 10 bits. This is an example of lossy compression which MP3 encoding uses. In this compression method, part of the data is lost thus reduced quality but bandwidth and storage space is saved.

So what’s the difference between CD quality audio and Mp3 audio quality?

To put it in simple terms, mp3 encoding is lossy which leads to lower quality audio as compared to CD quality. Currently, CD quality audio offers one of the best audio quality at manageable sizes. When creating digital cd quality audio, the analog music signal is sampled 44,100 times in a second to create a digital file that can be processed by a digital signal processor like an MP3 player, phone, computer etc. The main difference between CD quality audio and mp3 audio comes from the compression algorithm used for mp3. The lossy algorithm leads to the loss of some bits that were obtained from the sampling stage of the DAC process. Consequently, this leads to a poorly reconstructed audio signal from the incomplete digital information that is used for the conversion back to analog.

What is High Resolution Audio?

High resolution audio seeks to produce higher quality audio, better than CD quality by either increasing the sampling rate i.e. higher than 44.1 KHz or by using a new compression method that loses as little information as possible. Sony is already producing devices which support this technology but I am yet to get more information about their methods.

Is HRA necessary?

Just like the eye has a limit to the number of pixels it can distinguish on a screen, the human ear also has a limit to the frequency range it can hear. For more information about that you can google the audible audio range for the human ear (20 Hz-20 kHz).

The sampling rate of 44.1 KHz was not a random guess by scientists. Mathematically, at this rate, the reproduced audio from the DAC process described earlier is almost identical to the original analog audio quality.

HRA seeks to employ a higher sampling rate than this to produce better sounding music players. The question is, will the difference be noticeable to the normal user? Will the audio quality be better to warrant the development of new hardware to decompress the higher bit rate audio quality? Will the devices be cheap enough to replace current DSP devices like mp3 players, smart phones etc.? To answer those questions, I need a HRA audio device and the best sound reproducing speakers/headphones.

All in all, it doesn’t hurt to have a device that can handle higher bit rate audio. Let’s wait for 2014 and see whether this technology will pick up or whether it will be a nonstarter, like plenoptic photography in 2013. What is plenoptic photography you ask? Well that’s a story covered in another part of this blog.