Hi there! As you shop for new home theater equipment or tweak your current setup, you may come across two confusing technical terms – bitstream and PCM audio. What do these even mean and is one better than the other? Don‘t worry, I‘ll explain everything in simple terms so you can make sense of it all.
Let‘s start with the bottom line upfront: For most home theater setups, PCM is generally the better, more reliable choice over bitstream. PCM works on virtually all AV receivers and soundbars, provides consistent audio quality, and avoids many of the pitfalls of bitstream.
However, there are certain cases where bitstream can deliver improved audio, which I‘ll get into later. To help explain why PCM is preferable for many, let‘s first understand what bitstream and PCM are and how they work.
Demystifying Bitstream and PCM Audio
Bitstream is a method of transmitting compressed digital audio signals from a source device like a Blu-ray player to a receiver like a soundbar or AV receiver. The compressed audio codecs typically used in bitstream include:
- Dolby Digital (AC-3)
- Dolby Digital Plus
- Dolby TrueHD (lossless compression)
- DTS-HD Master Audio
According to Dolby, Dolby Digital Plus is used in over 5 billion devices worldwide as of 2018.
With bitstream transmission, the source device sends the compressed audio data to the receiver, which then needs to decode it in real-time to play the audio through your speakers.
PCM, which stands for Pulse Code Modulation, is an uncompressed audio format. The source device takes compressed audio (like Dolby Digital) and decodes it into multi-channel PCM digital data before sending it to the receiver.
Some common PCM formats are:
- LPCM (Linear PCM) – used on Blu-ray discs and streaming
- AIFF and WAV – used for audio recording/production
As per AES standars, LPCM supports up to 8 channels at up to 192 kHz sample rate.
Since PCM is already decoded by the source, the receiver simply converts the digital data into analog signals that amplify through your speakers without needing to decode anything.
Now that we know what each format entails, let‘s look at some key differences:
How Bitstream and PCM Audio Differ
While both bitstream and PCM can provide excellent quality audio, there are some important distinctions between them:
- Bitstream – Decoding is performed by the AV receiver or soundbar
- PCM – The source device like Blu-ray player handles decoding
According to professional AV installers, decoding is best performed by high-end source devices designed specifically for the task.
Surround Sound Codecs
- Bitstream – Can carry Dolby Atmos and DTS:X object-based surround
- PCM – Limited to legacy surround sound like Dolby Digital 5.1
Object-based audio like Dolby Atmos is supported in over 200,000 cinema screens worldwide.
- Bitstream – Depends on decoder quality in the receiver
- PCM – Guaranteed clear quality from source decoding
Based on audio testing, PCM achieves better Signal-to-Noise Ratio (SNR) and frequency response compared to lossy bitstream.
- Bitstream – Only compatible with equipment supporting digital audio
- PCM – Nearly universal playback compatibility
PCM is supported on 99% of AV receivers and soundbars on the market according to industry reports.
- Bitstream – Extra latency from real-time decoding
- PCM – Lower latency as audio is pre-decoded
Audiophile testing indicates PCM has at least 50ms lower latency compared to Dolby/DTS bitstreaming.
- Bitstream – Highly compressed streams
- PCM – Uncompressed so requires more bandwidth
Blu-ray Dolby TrueHD bitrate = 3.5 Mbps vs 24-bit/96 kHz 6-channel LPCM = 13.5 Mbps
- Bitstream – Can limit secondary audio capability
- PCM – Allows full secondary audio channels
LPCM on Blu-ray supports commentary, director narration, etc. on separate secondary channels.
As you can see, while both formats have their relative pros and cons, PCM clearly comes out ahead in key areas that impact audio quality and compatibility.
Next let‘s look at the specific benefits and drawbacks of each format in more detail.
Advantages and Disadvantages of Bitstream vs PCM
Pros of Bitstream Audio:
Enables Dolby Atmos and DTS:X – Object-based surround formats can only be transmitted via bitstream, not PCM.
Leverages AV receiver decoding – Can take advantage of specialized DSPs on higher-end receivers.
Efficient transmission – Highly compressed streams reduce bandwidth demands.
More control for AV receiver – Receiver handles all audio processing when decoding bitstream.
Higher potential audio quality If paired with high-end gear, bitstream can sound better than plain PCM.
Cons of Bitstream Audio:
Only works with digital audio equipment – Not compatible with analog-only receivers.
Extra decoding latency – Real-time encoding adds delays and lipsync issues.
No secondary audio channels – Secondary content muted or downmixed to primary audio.
Receiver-dependent quality – Varies based on the decoding capability of the receiver.
No surround sound at all if receiver lacks decoders – Gets converted to stereo PCM or muted entirely.
As you can see, bitstream has some benefits but also significant limitations compared to PCM. A high-end decoder and full digital connectivity are minimum requirements for acceptable bitstream performance.
Pros of PCM Audio:
Guaranteed reliably excellent quality – Quality fixed at source prior to transmission.
Works on virtually any audio equipment – Compatible with 99% of devices.
Enables secondary audio channels – Full commentary tracks preserved.
Lower latency – Avoid lip-sync issues since audiodecoded upfront.
No limitations on audio formats – Can contain high-res Dolby TrueHD, DTS-HD MA, etc.
Places no demands on receiver – Works perfectly even with basic receivers.
Cons of PCM Audio:
No support for Dolby Atmos or DTS:X – Requires bitstream for object-based audio.
Larger transmission bandwidth – Uncompressed streams take more space.
Audio quality limited to source decoding ability – A weak source device will result in poor quality PCM.
Forces source device to do all decoding – Increased processing load on player.
Again, the pros of PCM clearly outweigh the cons for most home theaters. The only exception is if Dolby Atmos or DTS:X support is required.
Comparing Bitstream vs PCM Sound Quality
Given the differences above, which format offers better sound quality? Let‘s compare:
PCM provides more reliably excellent audio since the quality is fixed at the source prior to transmission. This guarantees robust audio regardless of your receiver‘s capability.
Professional reviewers confirm that PCM achieves better frequency response, dynamic range, distortion performance and SNR measurements across diverse testing.
Bitstream can achieve superior quality – but only when paired with high-end AV receivers or processors designed for optimal decoding. It also requires properly set up speakers and acoustic treatment to realize this potential.
In formal listening tests, audio experts could barely distinguish Dolby TrueHD from uncompressed LPCM when both were decoded by high-end playback systems.
So in summary:
- PCM ensures consistently great quality on any equipment
- Bitstream only sounds better on very high-end home theaters
- On average/budget gear, PCM likely provides better sound
I recommend starting with PCM to guarantee excellent audio. Try switching to bitstream later if your gear meets the demands.
Choosing Between PCM vs Bitstream
Based on your specific needs and equipment, here are some tips on selecting the right audio format:
✅ For basic stereo, 5.1 or 7.1 surround sound – PCM is all you need.
✅ For Dolby Atmos or DTS:X playback – Bitstream is required.
✅ If your receiver supports advanced codecs – Try bitstream to use its decoding.
✅ Lower-end or older receiver – Stick with PCM for reliable quality.
✅ Need universal compatibility? – Use PCM to maximize device support.
✅ To preserve secondary audio – PCM transmits full commentary channels.
✅ Concerned about latency? – PCM has less delay and lip-sync issues.
I suggest testing both PCM and bitstream formats with a variety of content to hear which sounds better to your ears based on your specific equipment.
Recommended Audio Settings
Here are some best practice audio configurations for common home theater setups:
Beginner soundbar – Use PCM since basic soundbars won‘t properly decode complex bitstreams.
Enthusiast AV receiver & Blu-ray player – Try both PCM and bitstream to compare sound quality.
High-end OLED TV & mid-range AV receiver – Stick with PCM to take advantage of the TV‘s excellent onboard decoding.
Dolby Atmos soundbar – Use bitstream to get Dolby Atmos from media devices.
Projector with analog audio output only – PCM is required since projector lacks digital audio connectivity.
Streaming on Nvidia Shield into a A/V receiver – Shield can decode Dolby Atmos into Dolby MAT so PCM is recommended.
No matter what combination of source device and home theater receiver you have, start with PCM as your default, preferred audio format. Then experiment with bitstream if you have higher-end gear and wish to try leveraging its decoding capabilities.
Bitstream vs PCM for Gaming and Streaming
Let‘s also quickly touch on audio settings for gaming and streaming:
For game consoles, PCM is ideal to ensure lag-free audio directly from the source.
Dolby Atmos gaming requires bitstream for Xbox, but Sony PlayStation properly outputs Atmos via PCM.
Most streaming devices like the Apple TV 4K have excellent onboard decoding best leveraged via PCM output.
If your TV supports Dolby Vision with Dolby Atmos passthrough, using PCM may allow transferring both signal formats to your AV receiver.
Again PCM provides key benefits like reliance on the high-quality decoding built into gaming consoles and streamers. It also avoids lip sync problems caused by additional bitstream decoding.
Why PCM is the Best Choice for Most Users
To summarize everything we‘ve discussed about bitstream vs PCM:
- ✅ PCM is supported on virtually any AV receiver or soundbar
- ✅ It provides reliably excellent audio quality from source decoding
- ✅ There is zero risk of poor audio due to receiver incompatibility
- ✅ PCM has lower latency for better lip syncing
- ✅ Secondary audio channels remain available
- ✅ No specialized digital audio equipment is required
- ✅ There are zero demanding technical requirements
For all these reasons, PCM is the safest, most universal audio format that guarantees great sound on any setup. It just works!
The only drawback is lack of Dolby Atmos or DTS:X support. But this is irrelevant for basic stereo or surround systems.
Bottom line – For reliable, excellent quality audio on any equipment, choose PCM.
Only consider bitstream if you have an expensive, high-end Dolby Atmos/DTS:X home theater and wish to experiment with improved sound. Even then, beware that bitstream can actually deliver worse audio if your gear isn‘t cutting-edge.
I hope this detailed look at bitstream vs PCM demystifies these formats and helps you configure perfect audio! Let me know if you have any other questions.