Dolby Digital vs. PCM: 5 Must-Know Facts
- Dolby Digital is a 5.1 surround sound format, while PCM is a 2-channel stereo format.
- Dolby Digital was developed by Dolby Laboratories in 1976, while PCM was developed by Fraunhofer (formerly known as “Hermann von Helmholtz Institut,” the German name for the Institute of Physics and Technology) in 1965.
- Dolby Digital is for multi-channel applications, including surround sound for home theaters, film audio, and similar purposes.
- A Dolby Digital soundtrack consists of six channels: left channel (L), center channel (C), right channel (R), left surround channel (LS), right surround channel (RS), and subwoofer(s).
- A PCM soundtrack consists of two channels: the left channel (L) and the right channel (R).
Dolby Digital is a lossy compression of multichannel audio format used for storing and transmitting digital audio data on optical discs like CD-ROMs and DVD-ROMs and in computer media. It is also commonly known as DD, or simply 5.1 surround sound.
Dolby Digital is the most common digital audio compression scheme in commercial digital audio media, such as DVDs, CDs, and Blu-ray Discs. Dolby Laboratories originally developed it and has been licensed to various companies since its development in 1988.
PCM stands for Pulse Code Modulation, the encoding method used to deliver digital sound. The PCM signal is converted into an analog waveform, then converted back into a digital signal by a Digital-to-Analog Converter (DAC).
The DAC determines how much amplitude will present in each audio information sample. A low-pass filter then converts the amplitude of each sample to a voltage level. This signal is sent to your speakers, causing them to vibrate and produce sound waves.
Both Dolby Digital and PCM can tailor to converting audio recordings. Whereas PCM relies on the uncompressed conversion of analog sounds to digital, Dolby Digital practices a 5-7 channel setup. From a technical perspective, users prefer Dolby over PCM due to higher channels, but the output’s quality matters greatly too.
However, this is not enough knowledge to decide on which format would be best for your needs. In this Dolby Digital vs. PCM guide, we will compare and contrast the specs and performance of the two audio formats to help you make an informed decision.
Dolby Digital vs. PCM: A Side-by-Side Comparison
|Number of Channels
|5.1 or 6. The 5 channels include the front left, the front right, center, surround left, and surround right
|2-channel digital. The channels are the left channel (L) and right channel (R)
|Lossy audio format
|Analog audio format
|S/PDIF, IEEE 1394, HDMI
|HDMI, digital coaxial, digital optical
|Blu-ray Disc Data Rate
|Uncompressed, raw files
|DVD Data Rate
|488 or 384kbps
|Does not support compatibility extension, but does support matrix encoding/decoding of two-channel audio signals (Pro Logic)
|Supports compatibility extension
|Pulse Width Error
|Dolby Digital uses higher-frequency subcarrier modulation implementation to become more vulnerable to pulse width error during the transmission
|PCM audio reduces the pulse width error of transmitted signal due to its low-frequency subcarrier modulation implementation
Dolby Digital vs. PCM: What Are the Differences?
So far, we understand the fundamental dynamics of Dolby Digital and PCM, but you need an in-depth illustration of their features, pros, and cons.
What is Dolby Digital?
Dolby Digital is a 5.1 surround sound format that has become popular for playing DVDs and Blu-ray discs on home theater systems. It uses an encoded audio signal that contains both the front left, center, and right channels and the surrounding left, surrounding right, and subwoofer channels.
Dolby Digital has many features that separate it from the competition.
Dolby Digital offers an uncompressed audio format that delivers the highest quality sound. Dolby Digital is a lossless format and does not lose any information passing through a transmission or storage medium. The result is that your music will sound as good as it does in your home or office, even at higher volumes.
Advanced Noise Reduction
Dolby Digital uses advanced noise reduction technology to produce a better-quality image with less background noise. It means you can enjoy movies without turning the volume up too high to drown out sounds from other sources—like people talking or street traffic—which can occur with non-Dolby Digital sources.
Enhanced Bass Output
The enhanced bass output of Dolby Digital means more precise and powerful bass frequencies than those available in other formats like SACD or DVD-A. It makes it ideal for use in home theaters where you’re looking for more bass than what’s provided by traditional audio setups, such as speakers and subwoofers.
Full 5.1 Surround Sound
Dolby Digital is the original 5.1 surround sound format and the only one that has been around since its inception in the 1980s.
It uses Dolby Pro Logic II decoding to create a 5-channel surround sound experience that can play on any existing stereo or home theatre system with two speakers or more.
- Better Sound Quality
Dolby Digital uses a higher sampling rate than other formats, Dolby Digital can deliver more accurate sound reproduction than other formats. It means you get better sound quality when you record with a Dolby Digital recorder or play back your recordings on an audio system that supports Dolby Digital.
Remixing for Surround Sound
Dolby Digital is a technology that allows you to mix sound from multiple speakers into a single audio stream. This means you can listen to your music in the back seat of a car or even in a bathroom without worrying about losing any details. You can also use Dolby Digital on your TV and home theater system for a truly immersive listening experience.
Advantages of Dolby Digital
- Enhanced sound experience: The best thing about Dolby Digital is that it delivers richer, more detailed sound than other formats, like SACD or DVD-Audio. It is ideal for high-resolution music and video, which can be difficult to reproduce with lesser audio formats.
- High bit rate support: Dolby Digital supports high bit rates that enable your system to handle large files without losing quality or performance. For example, a movie encoded into Dolby Digital 5.1 has a bit rate of 2205 kbps (kilobits per second), which is higher than SACD’s 1509 kbps and DVD-Audio’s 1252 kbps.
- Stable quality over time: Dolby Digital ensures stable quality over time thanks to its advanced error correction code (ECC). It makes it possible for you to use your system regardless of how much data you transfer or store over time.
- Availability of bitstream encoder: The availability of a bitstream encoder is one of the major advantages of Dolby Digital. The bitstream encoder is a hardware or software entity that converts digital signals into analog signals that a sound reproduction system can use. The bitstream encoder can be installed on a PC, or it can be installed as a separate module in the sound card. Bitstream encoding software is available for Windows and Macintosh operating systems.
- Flexibility in mixing: The biggest advantage of Dolby Digital is that it gives you the flexibility to mix your audio track in any way you want. You can add effects, EQ, and other processing to your audio track and then save the file with different surround sound modes so it can play through any set of speakers. Dolby Digital allows you to change the gain on each channel individually, which provides more options for adjusting the volume of specific elements within a scene. You can fine-tune individual sounds without making large adjustments across multiple channels.
- Improvement in metadata: A major advantage of Dolby Digital is the improvement in metadata. With Dolby Surround and DTS, you can use a single audio stream for all five channels. The same source material encoded differently will have different bitrates and, therefore, different file sizes. The Dolby Digital audio stream is fully compatible with standard DVD players, so you don’t have to worry about conversion problems.
Disadvantages of Dolby Digital
- Signal loss: The signal can be lost in high-frequency ranges, meaning that when you play a DVD with a Dolby Digital track, you may lose some of the higher frequencies from your sound system.
- Lack of bass in certain types of music: This is because it takes up more bandwidth than analog signals, so there isn’t enough left over for the bass to affect the sound quality of your movie or music.
- Increased cost: The most common disadvantage of Dolby Digital is the increased cost. With Dolby Digital encoding, each channel needs to be encoded separately. This can increase the amount of data needed to encode an HD movie, which can be costly if done on a large scale. In addition, it may also require more expensive equipment and higher-quality encoders to accomplish the task.
What is PCM?
PCM stands for pulse code modulation. It’s an older technology that encoded audio signals before Dolby Digital was developed. It doesn’t use any compression techniques to reduce file size. Still, it can’t be used with newer software or devices because it’s not fully compatible with modern standards such as Dolby Surround or DTS Neo:6.
The main features of PCM include the following, as listed below.
Linearity is the ability of a pulse-code modulation (PCM) signal to have the same amplitude at any point in time. In other words, if you have a PCM signal, it should be able to reproduce all cycles without distortion. Linearity is important for many reasons.
For example, if you are using audio compression or transmission, you need to ensure that your audio doesn’t get distorted by changing its amplitude. If there is too much distortion in your audio, it will sound bad and be hard to hear.
- Frequency Response
The frequency response of a pulse-code modulation (PCM) system is the ability of the receiver to reproduce signals at specific frequencies in the range of interest. It is usually defined as the set of all values within a given bandwidth that will be detected as data. In an audio system, it is usually measured concerning an ideal sine wave.
It results in a number that indicates how well a given signal can be recovered from a given input level. This number may also include noise, distortion, or interference errors. In the case of video, the most common application of PCM systems is motion detection in video surveillance applications. This allows fast switching between images without lossy compression artifacts and requires additional bandwidth for each frame.
Dynamic range is the difference between the loudest and softest sounds a recording can reproduce. The dynamic range varies from one recording to another, but is generally between 94 dB and 109 dB at 1 kHz. The dynamic range of a digital audio file is measured in decibels (dB).
The higher the dynamic range, the better an audio file will sound. The dynamic range for a standard CD is about 95 dB. A typical DVD has a bit less dynamic range, at 90 dB. As you might expect, vinyl records have the highest dynamic range, at 120 dB or more.
The encoding delay is the time it takes for the data to be encoded and then decoded. In a digital system, this is typically one bit or two bits of information at a time. The longer the encoding delay, the more information can be sent in one clock cycle. A shorter delay will allow more information to be sent per cycle.
Advantages of PCM
- Higher data rate capability: PCM can achieve a higher data rate than those with other techniques, like AM or FM, because it does not require any extra processing steps for the frequency encoded information. This makes the PCM system work well with high-speed systems such as video and telephony applications.
- Less distortion: This means that the signal from a microphone is clearer and more accurate. This is because there is no background noise or interference from other frequencies that can distort the original sound.
- Compact bitstream: You can send any digital signal to a DAC or headphone amp and have the music come out in PCM format. This is great for anyone who wants to use their headphones or DACs and doesn’t want to worry about converting from any other format.
Disadvantages of PCM
- The data is encoded at the transmitter side, which means that the receiver has to decode the signal first before decoding the data.
- The data is not quickly transmitted unless it is in a higher frequency band than other signals.
Dolby Digital vs. PCM: Which is Better?
The two formats are not directly comparable as they have different features.
PCM is uncompressed raw audio. Dolby Digital is compressed audio (somewhat like an MP3), which is essentially the PCM version and compressed in a lossy manner.
So, in general, PCM will sound better, since the Dolby Digital version is made from it. Dolby Digital has been designed for professional applications, such as post-production and broadcast, where quality is paramount. The PCM audio format was designed for consumer applications like CD/DVD recorders and car stereos where quality isn’t as important.
Ultimately, users need to decide whether they need compressed or uncompressed audio and which related features mean the most to them in their audio experience.