Bitstream vs. PCM for Audio – Which Is Better?
PCM (Pulse Code Modulation) and Bitstream are two industry-standard forms of audio transmission from a source to a receiver. The main difference between the two is the decoding process of the compressed files. While the quality is the same, compatible devices and supported frequencies vary.
PCM is the Pulse Code Modulation, while Bitstream is a general name associated with any type of digital sound transmission. Bitstream is encoded in digital signals format in binary form or transmission over channels. In contrast, PCM is the old standard for encoding audio in CDs, DVDs, and Blu-ray discs.
Bitstream is famous for its cost-effective performance as it retains the CD-quality sound with a reduced bandwidth and storage requirements.
Both features help a lot for audio transmission from media players and transmitters to the receivers of speakers or home theater systems. Although PCM and Bitstream are similar and comparable technology, they have slight nuances in terms of how data is encoded and compressed.
Differences Between PCM and Bitstream
While both formats provide you with high-quality audio, there are some subtle differences between the two. Both have their advantages and disadvantages, and one is not better than the other.
One of the major differences between PCM and Bitstream is their compatibility with different media players. PCM is compatible with most DVD, CD, and Blu-ray players as it sends 2-channel signals. Bitstream is compatible with high-end modern players, which support surround sound formats.
While PCM is more flexible and can work with almost any media player, Bitstream mainly works with modern devices that have hi-res surround sound format support.
Another significant difference is with the audio files that both PCM and Bitstream work with. With the PCM, media players convert audio between digital and analog formats for transmission. But, Bitstream uses encoded audio files which come in specific surround sound formats for digital transmission.
With the PCM audio output, the media player will decode files such as Dolby, DTS HD, DTS, and Dolby TrueHD audio codecs. Bitstream uses audio compression, which results in better audio codecs for output like Dolby Atmos, Dolby TrueHD, DTS HD Master Audio, and DTS: X.
If you are using PCM, the audio files are decoded by the players before being sent to the receiver. Bitstream, however, works with compressed audio files sent to the receiver before they are decoded by the receiver. With the PCM and Bitstream, different parts of the system are responsible for decoding the audio files.
The connection types of PCM and Bitstream are also different. While PCM requires a physical connection between the player and the AVR and the speaker, Bitstream can work wired or wireless, being able to transmit audio streams via different mediums, as long as it is from a compatible media player.
So, if you are using a wireless setup, then Bitstream is the ideal choice for you. Suppose you are using cables as your connection medium; you can go for PCM or Bitstream as you like.
The audio output is another key difference between the two transmission formats. The PCM transmission uses a much higher bandwidth to minimize quality loss for a better output. However, the Bitstream transmission is more versatile for receivers and speakers to provide high-quality audio.
In terms of secondary audio, PCM performs slightly better as it supports the high-resolution secondary audio channels much better. On the other hand, Bitstream also has good secondary audio support, but the options are not as versatile as it is with PCM.
The issue of Bitstream’s secondary audio support starts when the file uses hi-res secondary audio formats like DTS-HD, Dolby TrueHD, or anything higher. To transmit both audio formats into the same bandwidth, Bitstream decreases the quality to standard DTS or Dolby Digital, resulting in a downgraded audio quality.
PCM can work with receivers and players that support both digital and analog audio transmission, while Bitstream only works with receivers and players that support digital sound transfer.
With the Bitstream, the receiver is responsible for decoding and converting the digital audio signals to audio output. At the same time, PCM decodes and converts the audio signals in the player, sending the audio signals to the receiver after the process.
Optical / Coaxial
The PCM format supports a limited amount of digital optical or coaxial output options, while Bitstream is more versatile and supports both digital optical and coaxial output up to 5.1 systems. PCM only provides a two-channel signal.
Similarities Between PCM And Bitstream
Although Bitstream and PCM have many subtle differences, they are quite different in the formats they use, both can work well with most DVD and Blu-Ray players and provide high-quality audio. Also, both systems convert audio files to analog for the speakers to read them.
The only difference with the audio quality occurs when a secondary audio output with higher resolution codecs is in the system. Besides that, the audio quality difference between both configurations is not noticeable.
There are many players today that allow the users to set the audio settings to PCM or Bitstream as they like.
Both PCM and Bitstream use similar processes to provide volume output as they convert audio files to analog signals for the speakers. The conversion step and process are not the same, but the system is similar.
When To Use PCM?
The PCM configuration comes in handy for users looking for a faster connection without latency, high-res secondary audio, decoding and converting audio files in the player to relieve the receiver from the responsibility, high versatility, and compatibility.
Most DVD and Blu-ray disc players, even the older ones, support PCM, making the configuration highly versatile and compatible. If you have a relatively older player, the chances are high that your player supports PCM but not Bitstream.
Another important consideration is that PCM only works with wired connections. If you have a wireless sound system, PCM is not for you. However, PCM provides a better transmission performance than the wired system, delivering latency-free audio.
For the secondary audio output, PCM makes more sense than Bitstream as it can transmit high-res audio files with the wired system. The quality of secondary audio decreases with Bitstream as it uses compressed audio files.
When To Use Bitstream?
Bitstream is for people who want to use a 5.1 surround sound system, give their sound system more versatility and flexibility when playing hi-res audio, have a strong receiver for decoding and processing files, and want to use a wireless system.
While the sound quality of both configurations is very similar, Bitstream has the potential to deliver slightly higher-quality audio if it is used with a high-end receiver that has a top-notch processing capacity. As Bitstream relies on the receiver to convert and encode the audio signals, the performance of the receiver heavily affects the quality.
The Bitstream configuration supports 5.1 surround sound when digital optical or coaxial connections are used. So, the sound system gets more flexible with the Bitstream configuration.
However, the most important reason people prefer Bitstream is the option for wireless connection. Bitstream uses compressed audio files to transmit them wirelessly. The drawback is that the secondary audio quality will be limited with the Bitstream. Instead of hi-res, the secondary audio decreases the standard resolution.
The other drawback is that Bitsream heavily depends on the performance of your receiver and sound system. If you want a noticeable difference with PCM configuration, you will need high-end receivers and sound systems.
Should I have my TV on Bitstream or PCM?
If you are not using a sound system, the best configuration to use is PCM. If you use Bitstream without a sound system or a soundbar, the TV will be responsible for processing the audio, which would result in reduced volume and loss in quality.
If you are using a sound system or a soundbar, then depending on your system, you can go with the bitstream or PCM configuration.
What is LPCM?
Linear pulse code modulation (LPCM) is an audio transmission configuration with uncompressed audio files. It is also called PCM Plus, and it has linearly uniform quantization levels instead of the different quantization levels of PCM that change with the amplitude.
Except for the sample rate and quantization precision, the system and process for LPCM and PCM are the same.
LPCM uses AU Audio, AC3 (Dolby Digital), raw audio, WAV, AIFF (Audio Interchange File Format), RF64, and MPEG audio. It works only with an HDMI connection or via optical or coaxial.
To wrap things up, I can say that there is no clear winner in comparing PCM and Bitstream. Both have their advantages and disadvantages, as well as different environments in which they perform best. The decision is up to you and your system.
Both configurations deliver high-quality audio, but if you are after hi-res secondary audio, you will have to go with PCM. But, if you own a high-end home theater receiver and sound system, Bitstream allows you to take advantage of better audio codecs and use a wireless connection.