Deep dive into the space of Electronics — Part 3
As a matter of relaxing events during the weekend, there is this one thing that has been always close to my heart since my childhood times. The one thing that really heals my mind after having a tiring day or a bad day is Music. With this thought carrying in mind for over a decade now, I won’t mind calling myself a ‘Melophile’, well yeah there is a word for music lovers as well !!!
Being born in the late 90s and growing up in the early 2000s makes me go all nostalgic and vibe to the Indian indie-pop music albums till today, that used to come on the radio or on some limited music channels on the television before the internet came in.
My inclination for listening to music started at a very young age (7–8 yrs) and there is a very strange reason behind it — hailing from Bombay city (not suburbs) and a native town like Goa (Vagator), the proximity of the house to sea and beaches has made it possible to enjoy the serene nature around by watching the evening sunset with the waves of water striking through the tetrapods or the water just being soaked up in the sand and listening to Walkman- mp3 player which I used to have at that time.
I believe that being attached to a particular thing in life always teaches or benefits an individual in some or the other way and I would like to list down some of the famous quotes on music that I can relate to myself in real life.
- “Music is to the soul what words are to the mind.” — Modest Mouse
- “Music is the language of memory.” — Jodi Picoult
- “Music washes away from the soul the dust of everyday life.” — Berthold Auerbach
- “If people take anything from my music, it should be motivation to know that anything is possible as long as you keep working at it and don’t back down.” — Eminem
After discussing my fascination with listening to music, now I would like to switch to my engineering mind and correlate it with the topic right away associated with the generation of music!
iPod Shuffle/MP3 players (No Bluetooth)
Being a music lover, I was fortunate enough to have some amazing MP3 players during my school days which never failed to elevate my mood!
Having such devices at that time was like owning a BMW. Owing to this, I have taken the utmost care of them and have used them for almost a decade until when they stopped functioning just a few years ago which further led me to tear them down and study electronics inside them.
Here are my two music players:
Out of the above two, the iPod shuffle (right) was my favourite device that was very small and portable in size, with a single socket for charging & earphone input along with a 2GB memory of music storage which was sufficient for me at the age of 12.
But if we talk in today’s time this size will be peanuts. Along with this, it also has a clip like support at the back of it which can be attached to our clothes while walking/running/jogging thus solving the problem of keeping it in the hand or in the pocket every time.
Since I am not being able to recollect the brand of the mp3 player (left) as it was bought from a middle east country at that time(10–12 years ago).
I need to study this product a bit before making any conclusions and I would like to discuss this type of MP3 player in my embedded systems article coming up in future as it consists of components like operating system, LCD screen display, and button control.
But I would like to just mention the difference it has as compared to iPod shuffle which is — an additional LCD screen with 4GB of storage memory and separate ports for charging and headphone input.
After getting a glimpse of the devices which I used, now I would like to discuss some of the main characteristics of such devices —
Definition:
An MP3 player or Digital Audio Player is an electronic device that can play digital audio files. It is a small and portable piece of equipment, of less size than a CD player. MP3 players work in conjunction with personal computers, by which songs may be downloaded onto the devices.
Types:
a.) Devices that play CDs — They can be used to play both audio CDs and other data CDs containing MP3 or other digital audio files.
b.) Pocket devices — These are solid-state devices that hold digital audio files on internal or external media, such as memory cards. Devices that read digital audio files from a hard drive. These players have higher capacities, ranging from 1.5GB to 100GB, depending on the hard drive technology.
Digital Signal Processing — Transformation from CD to MP3
Normally a CD stores a song as digital information. The data on a CD uses an uncompressed, high-resolution format which is very large in size.
The goal of using MP3 is to compress a CD-quality song by a factor of 10 to 14 without noticeably affecting the CD-quality sound.
With MP3, a 32-megabyte song on a CD compresses down to about 3 MB. This lets you download a song much more quickly, and store hundreds of songs on your computer’s hard disk. MP3 is an example of digital technology, which means sounds you hear are stored in numerical form. CDs are digital too, but older music formats (including phonographs) used analog technology which means the music was stored as a physical or magnetic representation of the original sound, without using any numbers at all.
The key to storing music in digital format is a process called sampling — and it’s a kind of “music by numbers.” MP3s and CDs work in a similar way as playing the piano. At the time of recording, a computer “listens” to the music track that’s being recorded and “samples” the volumes and frequencies of the sounds: about 44,000 times each second, it analyzes all the sounds it can hear and converts them into a number.
This process is carried out by an ADC, which turns sounds (analog) into streams of numbers (digital), which are then stored in sequence in an MP3 file or on a CD.
When the file or CD is played back later, the reverse process happens: a DAC turns the numbers back into analog electrical signals that become sounds when they’re fed into a loudspeaker. The faster the computer samples (the higher the sampling rate), the more information it captures each time (the higher the bit depth), and more detail it captures each second (the higher the bit rate), the more closely the digital file resembles the original analog sounds and the higher the quality of the recording.
Compression is the secret behind all kinds of digital technologies, including digital photos, music downloads, and a whole lot more….
I know you must be wondering now where is the hardware stuff inside the iPod shuffle!!!
Don’t worry much as I will be coming to that part soon but prior to that, it is necessary to know some concepts because the real secret of a digital music player is not the gadget in your hand but the clever technology behind the MP3 files it’s playing!
MP3 player in general uses the lossy compression technique. I would like to explain this compression technique in simple language —
For example a message like: “I think I might pay you a visit later this week. I do hope that’s alright. Maybe you could reply and let me know if it’s convenient?” is compressed into “Visiting later in week. Hope OK. Let me know.”
Thus, the 27 words of the original message become 9 words. We could compress the message even further, but if we take out more words, it’ll soon stop making sense.
MP3 file storing:
Inside an MP3 file, music is stored as long strings of bits (binary numbers, zeros and ones) in a series of chunks called frames.
Each frame starts with a short header (a kind of table of contents), followed by the music data itself.
At the start of an MP3 file, there is a kind of “index card” that stores details of the track name, artist, genre, and so on. This information is called metadata and each part of it (artist, track, and so on) is stored in what’s called an ID3 tag.
Hence, this is how the MP3 data is processed.
iPod Shuffle!
So now let’s dig up the parts one by one and know their functions.
A thin line surrounds the clip section which suggests that this is the access for internal parts and so pulling on the clip opened up the iPod.
- Battery: The battery found inside the iPod Shuffle is a lithium-ion battery with a capacity of 0.192Whr which is equivalent to a 52mAh battery (the battery voltage is stated as being 3.7). While the battery, itself, may be very small in both size and capacity, the device does not contain a screen which is usually a power-hungry component that makes the single port design for charging and hearing input sound logical.
- Front buttons: The buttons on the iPod are situated behind the main PCB and separated with a piece of aluminium. Removing the internal components and screws reveals the flexible material that holds the tactile switches. The side of the iPod has the power button (which also functions as an option for either linear playing or random playing), the voice-over button for battery status, and the USB/earphone port.
- PCB: The main PCB consists of many small surface-mount components and one very large IC on the backside. A ribbon connector can be seen on the top side of the PCB which connects the board to the front buttons. The top side also contains the buttons found on the side of the iPod shuffle and the LED indicator.
With a bit of digging and some electronics knowledge, let's see the IC’s associated with it.
- The first IC (top left)sits on the top side of the PCB and has Apple written on it, this is probably the SoC that controls the iPod.
- The second IC on the iPod Shuffle is found on the backside and has a QR sticker stuck to it. However, considering the physical size of the IC, this must be the 2GB NAND flash that is used for music and file storage.
Let’s summarize its technical components in all!
- Microcontroller — Samsung System-on-a-chip, based around an ARM processor.
- Battery — Internal Recyclable Lithium-Ion Batteries
- Storage Medium — Flash Memory
- Audio Chip — Cirrus Logic Audio Codec Chip
Working:
- Hardware: If MP3s are computer files, it follows that MP3 players must be computers. An iPod or MP3 player has an input (USB docking lead that hooks it up to your computer), a memory (either a small hard drive or a flash memory that can store MP3 files), a processor (something that can read the MP3 files and turn them back into music), and an output (a socket where you plug in your headphones).
- Software: iTunes is the integrated jukebox/media-player software that comes with an iPod. It lives on your computer, and you use it for organizing, playing, converting and downloading files from an external source to your computer and from your computer to an iPod. This is really no different from the software that comes with any other portable media player. The iTunes software auto syncs with iPod whenever it’s connected to your computer through a USB 2.0 port. Just plug it in, and the iPod automatically downloads every new file that you added to your iTunes jukebox since the last time it was connected. It also uploads to iTunes all new data that you added to your iPod since last the two conversed, like playlists and song ratings.
- Now switch on your iPod to play your favourite track and it works just like a computer.
- The processor chip loads an MP3 file, reads the ID3 index cards, and displays the artist and track name on the display.
- Next, it works its way through the MP3 file reading each frame in turn. It reads the header, followed by the data, and turns the digital information (the binary ones and zeros) back into sound frequencies that your ears and your brain decode as music.
Miscellaneous
Some of the characteristics which were not mentioned above are listed below!
Features
a) Portability: An MP3 can be taken anywhere since the player is so small it can easily fit inside a pocket. Some models, like the iPod Shuffle (as mentioned above), are no bigger than a person’s thumb.
b) Accessibility: MP3 players do not have to be plugged in to be played. They may be listened to at any time, even while the user is exercising or in transit. They also do not require changing CDs, as does a CD walkman.
c) Battery Powered: The batteries of MP3 players are rechargeable. Most MP3 players are charged when plugged into a computer using a USB port, but there are also external chargers that plug into the wall.
d) Display Files: Some MP3 players have display screens that reveal the names of tracks, option lists, and volume. There are even MP3 players that are capable of playing digital video files.
e) Storage: The smallest MP3 players store about 1GB of data, but that is still enough to store about 10 full-length albums. The larger MP3 players can store nearly 100 GB, which may match a personal computer’s entire music library.
So as you know how an iPod shuffle works in all, I would like to end this article by mentioning a site reference where you can compare various types of music players in all!
In addition to this, if you are aware of some pocket-friendly devices developed solely for music purposes inside or outside India do let me know in the comments!
Until then see you next weekend!
Thank you!
