The Basics of PCM
And Bitstream Audio — Which Is Better?
What is the difference between PCM and Bitstream? Which is better?
Bitstream audio makes use of the digital decoding process to convert the digital file into an analog signal. It is the simplest form of digital audio transfer as digital data is decoded without converting into analog. Outputs can be speakers, or DACs, or even another digital device. The drawback of this system is that it is prone to electrical digital noise and distortion, producing an inconsistent and imperfect issue of the converted content. Therefore, there is a need to constantly monitor the audio for quality control and/or ask the content providers to re-encode the audio to maintain the desired quality standards.
PCM is a form of digital audio that happens to be the most common way of transporting audio content for the purposes of either transmission or storage. Here, the digital signal is kept in its original form.
For example, a recording that had PCM encoding will be able to be played wherever a player capable of decoding the content is available. However, the digitization process may differ from one device to another. PCM technology allows for a uniform audio output quality with no distortion. This is due to the fact that the audio is not converted from digital to analog, and then converted back to digital again. PCM audio maintains its quality through the digitization process and is unlikely to see any degradation in quality.
The Basics of Bitstream
Vs. PCM for Audio
An audio system can be compared to a programming language like C or Python. The PCM system is akin to the baby steps of an infant, and the bitstream is the giant leap as the child grows.
PCM is pristine like a mime, it’s all about noiseless information while bitstream is audio straight from the horse’s mouth as the loudest flute at a renaissance fair.
Bitstream = WAV
PCM is only capable of outputting a mono or stereo audio signal; but the bitstream can output virtually every audio signal format known to man if you've got the ducats to pay for a DAC (digital-to-analog converter) capable of handling it. Put simply, the bitstream can output anything from a fax machine to the 9th harmonic of a 3rd octave C note off a glockenspiel with the right gear.
The audio bitstream is a wider bandwidth, a digital signal and user generated files, so it’s NOT the same as a CD.
Digital files are like a full spectrum of color, while analog files are like the black and white picture in a coloring book.
Bitstream vs. PCM – Side by Side Comparison
Most modern receivers and AVRs have audio decoding that can accept signals in bitstream and PCM formats. To choose the optimal format, you'll need to understand the difference between the two.
PCM stands for pulse code modulation. It's a system that processes sound encoded on a disc into a digital signal and sends it to your speakers. PCM is a popular format for DVD audio. When an audio source is encoded in PCM, it's somewhat altered from its original format. For this reason, it's known as lossy compression.
Bitstream is a bit different. It encodes the signal directly from the source to the processing module using a format that doesn't change the audio with the help of uncompressed data. For this reason, it's known as lossless compression. This is the default format for several types of surround sound and audio formats. When it comes to choosing the best lossless compression format for audio, bitstream is said to offer a more transparent and linear listening experience.
If your receiver or AVR has audio jacks that are labeled as bitstream or PCM, then you can try playing the audio tracks that you have encoded in either format and listen directly (without a decoder). If you have this capability, you can choose bitstream or PCM for the audio tracks that you want to play.
What Happens When You Choose PCM?
The first way your home entertainment system decodes an audio signal is the most common, and the system works the same for both PCM and bitstream. A digital-to-analog converter (DAC) converts a digital stream of ones and zeros to an analog signal. This is typically done with a digital-to-analog converter. The analog signal is then sent into the receiver for amplification. The receiver does the job of mixing the different channels together and creating a deep, cinematic sound.
The second method involves what some call bitstream, and others call it straight PCM. A bitstream audio connection is a continuous stream of data that contains not only critical audio information encoded as a bitstream, but also additional data, metadata, and a plethora of other information shepherded along with it.
All told, bitstream audio is a continuous stream that contains all the information about the audio signal that’s played through it.
As we said, both PCM and bitstream contain crucial audio information, such as the digital representation of the analog audio signal. The bitstream audio connection is better at delivering short, bursty sections of audio. It’s better than the first method for reproducing rapid peaks of high or low frequency, such as when a drummer strikes the drums, or when a vocalist sings high notes or growls.
What Happens When You Choose Bitstream?
Bitstreaming takes digital audio signals and translates them into an electrical current which is then transmitted to your speakers.
Using bitstream eliminates any signal loss caused by other processes, such as DACs (Digital to Analog Converters), and then transmitting this signal through a cable. Instead, the electric signal is received by your receiver and then converted back into sound.
What’s the benefit of bitstreaming versus PCM? It’s the elimination of these conversion processes, which is a big reason why bitstreaming gives you better sound quality. Also, bitstreaming eliminates the wait time between processing audio and playing it using PCM because it’s directly translated into the current.
Similarities Between PCM and Bitstream
Before we get into the differences, let’s explain what Bitstream and PCM are. PCM stands for Pulse Code Modulation and sometimes is referred to as LPCM (Linear Pulse Code Modulation). Bitstream is the name given to the digital representation of the audio data.
PCM and Bitstream both function using the same principle. In both cases, the analog signal is turned into a digital signal. PCM encodes the signal using sampled values and stores the result as a series of binary numbers. Bitstreams are a collection of binary numbers representing the sampled values. Bitstreams are different for each type of audio like DTS or Dolby, but the result is the same.
Now that we know a little about both PCM and Bitstream, let’s take a look at some of the differences within each of these types. These differences will help you to better understand when to use one over the other.
Differences Between PCM and Bitstream
Whenever you connect a device to a home theater receiver or a TV or when you play a Blu-ray Disc or a DVD, there’s a good chance you’re using either PCM or bitstream audio decoding.
If you’re not sure what that means or how to tell the difference, it’s time to get schooled.
Here’s the lowdown: Digital files containing audio (images, video or music) are broken down into ones and zeros transitioning between different states assigned a specific value also known as a “bit”. PCM is short for Pulse Code Modulation, and it’s a system of digital encoding for audio.
The source (for example a CD or a DVD) is broken down into a series of ones and zeros, and these bits are then decoded and converted back into audio when played by a compatible device. PCM uses a sample rate of 48 kHz and a bit depth of 24 bits, which means that the audio is not compressed and is played back exactly as it was recorded. When digital files are encoded as PCM, they are encoded in their “native” form.
Bitstream is an audio decoding technique used in home theater receivers and TVs.
When Should You Use PCM?
A common question among those just getting started with a home theater setup is whether to encode audio in PCM (pulse code modulation) or Bitstream format. Here's some background on this audio format debate.
In any audio setup, whether it's a home theater, a phone conversation, or a recording studio, you have to convert the incoming data to a form that your receiver, phone, or recording equipment can recognize and reproduce.
Currently, the standard for uncompressed audio is bitstream. You can find this on both Blu-ray discs and DVDs. The data is raw codecs, and the receiver, A/V receiver, or speaker system decodes the raw audio in special hardware that's built into the device.
PCM (Pulse Code Modulation) is similar to bitstream, but it doesn't require new hardware in the receiver. PCM is a method of transmitting compressed audio via a single channel, or digital stream.
PCM has been around much longer than bitstream, so you'll find it on virtually every source, whether it's a Blu-ray player, your TV, DVD or CD player, or your computer. The A/V receiver or speaker system converts back to analog, or uncompressed, audio.
When Should You Use Bitstream?
When you connect your audio components to your home theater receiver, you have an option of whether you want to let the receiver decode your audio signal or if you want to send it to your receiver in its native digital format. This is where bitstreaming comes into play.
Bitstreaming allows you to decode digital audio signals such as Dolby Digital or DTS. This can be used to send audio signals to your receiver if it didn’t have the capability to decode these signals itself.
With the digital signal being sent to the receiver, it can then process the audio signal. This should result in better audio quality. If this is the case, you may ask yourself why you should bother with decoding the digital signals yourself at all.
So why do you need to use your receiver to decode audio signals?
Is Bitstream or PCM a Better Option for Audio?
There are many people, both audio professionals and enthusiasts alike, who have heard of bitstream and PCM and know that one of these is the superior technology. The question is, which one is best for your setup?
Both bitstream and PCM have positive and negative aspects to them. Which one you choose really comes down to a specific application and needs. The best way to make a decision between them is to read up on each and decide what is most important to you.
Are you looking for the highest possible audio quality or are you looking for the most minimalist setup for your audio system? A bitstream signal will require more equipment and more processing than a PCM signal would. It is also an uncompressed signal, so the equipment will be more exacting to a high-powered receiver that can handle the signal accurately.
PCM is a lower-quality signal, so you may have concerns about the audio quality suffering if you are looking for the highest quality sound possible. However, many professional setups work with PCM signals, and the signal is generally very well understood. Because it is a much lower-quality signal, you will have less equipment required to attain a higher audio quality. A lower-quality signal also requires less processing on your part when choosing a receiver.
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I’m often asked which audio format is better for encoding music on CD – Bitstream, also known as Linear PCM (LPCM) or Pulse-Code Modulation (PCM).
The confusion plaguing the audio industry has been around since the introduction of the compact disc, and it’s obvious that, in the fullness of time, PCM and Pulse-Code Modulation (PCM) will do to the music world what Pulse-Code Modulation (PCM) did to the telephone world. Lol.