PCM and Bitstream are two audio formats you must know if you own a home theatre system or soundbar or are a sound enthusiast.
These two formats showcase how the audio signals travel from the source device to the speaker. In this case, the source device could be a Blu-ray player, gaming console, or PC.
But what do these two audio formats mean, and how do they differ? In this article, we’ll explain the basics of PCM and Bitstream and help you decide which is better.
Here’s what we will cover:
What is PCM?
PCM is an acronym for Pulse Code Modulation. In this, analogue audio signals are transformed into digital data.
This format is used in computers, DVDs and CDs. PCM is beneficial as it can operate and handle both uncompressed and compressed audio formats.
In devices supporting the PCM format, first, the device will decode the audio and then send it to the receiver, which will then play the audio. In the PCM format, the output device, such as the speaker, doesn’t do any decoding, and hence, users get a high level of fidelity and sound quality.
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What is Bitstream?
Bitstream format is also a way to send the audio data from the device to the output equipment. In this format, the audio signals comprise binary data or bits. This format is quite popular and is used by several top-notch surround sound systems.
Unlike PCM, the device doesn’t decode the audio format and sends it as it is. It is the job of the output equipment to decode the format. The receiver converts the Bitstream to PCM and plays it for you.
Bitstream format can also be used for wired and wireless transmissions, and the sound quality is similar to that of PCM. Sometimes, Bitstream’s sound quality is even more accurate than PCM’s.
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PCM vs Bitstream: Pros and cons
Both audio formats have their respective pros and cons that you should know before selecting the right one as per your preferences.
Here are some parameters that you should consider:
- Compatibility: PCM outperforms Bitstream in this department. More receivers support the PCM audio format, while the Bitstream format requires the speakers to support the device’s audio format. For example, if a source device is transmitting a Dolby Atmos Bitstream, the output device must also support it, otherwise, there will be miscommunication between the two and the sound output will be substandard. Thus, PCM is a safer and cheaper choice.
- Sound quality: The sound quality is similar in both audio formats. Both sound formats produce high-quality audio, including 3D audio. Usually, online streamers prefer Bitstream as the PCM process may lower the quality by a few points while decoding. On the other hand, many audiophiles and sound enthusiasts prefer PCM as there are little to no chances of decoding errors and delays.
- Secondary audio: In some cases, secondary audio is added to the primary one. This can include a commentary or a bonus feature. Usually, these secondary audio are coded in a lower quality. In PCM, the primary and secondary audio is decoded before the audio is transmitted to the output device. However, in Bitstream, only the primary audio is decoded, and hence, you will not be able to hear the secondary audio, or the sound quality will not be good.
Here’s a table with more parameters:
| Feature | PCM | Bitstream |
|---|---|---|
| Transmission | Compatible with analog and digital sound | Exclusive to digital sound transmission |
| Compatibility | Players decode and transfer data to the receiver | High-end players supporting various surround sound formats |
| Audio output | Requires higher bandwidth for quality output | Offers flexibility for high-quality audio output |
| Secondary audio | Better support for hi-res secondary audio | Limited channel options, but good secondary audio quality |
| Connection | Requires physical connection for audio stream | Supports wired or wireless audio streams from media players |
| Audio file | Transmits compressed files, the receiver decodes the data | Bit-encoded files following surround sound standards |
| Decoding | Converts analogue to digital for transmission | Transmits compressed files, receiver decodes the data |
| Optical/Coaxial | Minimal support for digital output | Supports up to 5.1 digital optical/coaxial output |
| Compression | Uncompressed | Compressed |
| Quality | Lossless | Lossy |
| Resolution | High | Varies |
| File size | Supports larger files | Supports smaller files |
| Data representation | Simple | Encoded data packets |
| Bit depth | Flexible | Variable |
| Dynamic range | Wide dynamic range | Dynamic range varies with bitrate |
| Encoding complexity | Low | High |
| Error resilience | Limited | Error correction |
| Metadata | Limited | Extensive |
| Editing flexibility | Limited | More options |
| System resources | Consumes more resources | Consumes relatively less resources |
| Use cases | Audio enthusiasts | Streaming |
PCM vs Bitstream: How to choose?
Now that we have understood the basic differences between PCM and Bitstream, how to choose between the two?
Here are some factors to help you to decide properly:
- If you possess an older device, the PCM format is the best choice for you.
- If you have recently bought a newer or high-end receiver or speaker, you can opt for Bitstream audio output.
- Next comes the secondary audio part. Here, PCM looks to be a better choice than Bitstream.
At the end of the day, it is your personal preference and the workflow that matters the most. For most of us, the minute differences in the sound quality don’t matter much. However, for those working in this field, you should take a minute, and understand the minute differences from the table above and decide further.
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