Have you ever wondered whether PCM or Bitstream are a better audio transmission method or which one’s better for your home theater system? Well, in this Bitstream vs. PCM guide, that’s exactly what we’ll get into. I’ll explain how these two affect your AV amplifier, Blu-ray player, soundbar, and the ability to play advanced formats like Dolby Atmos and DTS:X.
What is PCM (Pulse Code Modulation)?
How PCM Works
PCM, or “Pulse Code Modulation,” is the most basic and standard way to digitize analog signals. I always think of PCM as the “native language” of digital audio; it converts natural sounds into numbers by taking quick snapshots (samplings) of the sound wave at regular intervals.
For example, a CD audio signal is encoded at 16-bit and 44.1 kHz, which means it takes 44,000 samples every second, giving each sample a 16-bit number. It’s like taking thousands of tiny snapshots of the sound wave every second and then stitching them together to create a smooth, high-quality sound. Most modern devices, from smart TVs to game consoles to home theaters, understand and support PCM by default.
Use Cases and Device Compatibility
PCM is everywhere these days, from TVs and game consoles to streaming sticks and soundbars. When your device’s audio output is set to PCM and you use an HDMI or optical cable, the source device decodes audio like Dolby Digital or DTS and sends it to the receiver as raw PCM.
This method benefits older systems that don’t support more modern formats like Dolby TrueHD or DTS:X. I’ve used the PCM output when my home theater system couldn’t read these codecs, and I got full, high-quality sound from the player.
Advantages and Limitations
One of the main reasons PCM is so popular is that it’s compatible with almost everything. Because the audio is decoded and delivered to your receiver in PCM, you don’t have to worry about your audio system supporting more complex formats. You plug in the cable, and the sound is playing. There are no additional setup hassles or confusion about device support.
But there’s always a downside. PCM doesn’t carry any extra information or metadata, meaning you lose out on advanced features like the height channels in Dolby Atmos or the object-based effects in DTS:X.
Additionally, HDMI’s bandwidth limitations limit PCM to only seven main front channels and one bass channel (7.1), and there’s not enough room for anything more than that. So, PCM may not be the right choice if you want a more immersive experience with 3D audio effects.
PCM vs. Linear PCM (LPCM)
Linear PCM is a type of PCM in which the quantization levels are linearly spaced. This means that the step between each value is the same. While LPCM is a type of PCM, it is the most commonly used format of PCM in devices. So, when a device says it supports PCM, it almost always means Linear PCM.
What is Bitstream Audio?
How Bitstream Works
Bitstream sends compressed, encoded audio from the source to the receiver in the same format as originally recorded. It lets the player or receiver (like an AV Receiver or soundbar) handle the decoding. In other words, it’s like sending a zipped file without opening it and extracting it on the destination system.
When you set your audio output to Bitstream, your Blu-ray disc, game console, or streamer sends the same original Dolby Digital, DTS, or even Dolby Atmos data over the HDMI or optical cable, without any changes, and lets your sound system do the heavy lifting.
Bitstream Types: Dolby Digital, DTS, Atmos, and DTS:X
Bitstream is a high-speed highway for various audio formats. It can carry compressed Dolby Digital or Dolby Digital Plus audio on DVDs and streaming services. Furthermore, it can carry more accurate DTS or DTS-HD Master Audio remastering for Blu-rays and higher-quality media.
In addition, Bitstream can carry the lossless Dolby TrueHD files that music lovers love, and also, object-based formats like DTS:X and Dolby Atmos from source to receiver without any changes.
The key point is that Bitstream carries metadata, which tells your device where each sound should be played, the height, and the direction. When I upgraded my system to support Dolby Atmos, I quickly switched my audio output to Bitstream to take advantage of the full depth of the spatial sound and height channels.
Advantages and Limitations
Bitstream is useful for passing advanced multichannel audio formats like Dolby TrueHD or DTS:X without losing quality, which PCM can’t do. In this case, the compressed audio data is sent directly to your audio receiver (AVR) to be decoded, giving you the best possible sound quality, provided your hardware supports that format.
But Bitstream isn’t perfect. If your receiver doesn’t support a particular format, the device will fall back to a simpler format like DTS 5.1, resulting in a degraded surround sound experience.
Additionally, when you enable the feature of playing secondary audio, such as the director’s commentary, on some Blu-ray players, the player will automatically switch back to PCM and disable Bitstream.
So, if your sound system is modern and supports advanced formats, and you’re looking for a fully immersive audio experience, Bitstream is the best option. But if you’re unsure about your receiver’s decoding capabilities, go for PCM, which is simpler and less hassle.
Conclusion
This was my complete PCM or Bitstream guide. Now, you’ve thoroughly compared Bitstream vs. PCM and know all the differences between these two audio transmission methods. While Bitstream offers advantages in certain modern setups, PCM is still widely used in devices like gaming consoles and Blu-ray players.
