The Differences Between LPCM and PCM

Digital audio encoding formats have come a long way since CDs and MP3s first became widely popular. Now there is an array of digital audio encoding formats, each offering specific advantages over others. Two fairly popular audio encoding formats include LPCM and PCM. Both LPCM and PCM are digital audio encoding formats that are used to represent analog audio signals in a digital form.

In this article, we’ll examine their differences to help determine when each might best suit certain applications.

First, as a general comparison:

PCM (Pulse Code Modulation) is a general term that refers to various digital audio encoding schemes that are used to represent analog signals by sampling them at regular intervals and quantizing each sample into a digital value. LPCM, on the other hand, refers to a special form of PCM that is quantized linearly; meaning that the analog audio signal is sampled at regular intervals, and each sample is quantized with equal precision.

Read on to learn more.

Before continuing, you can also check out our similar articles in this series:

• PCM vs Bitstream
• PCM vs DSD Comparison
• Linear PCM vs Dolby/DTS

What is the PCM Audio Format?

PCM stands for pulse-code modulation and is a digital audio format designed to represent analog signals as digital. Please note that PCM is a general term that encompasses various digital audio encoding schemes.

However, generally speaking, PCM works by taking analog signals and turning them into a series of digital pulses that can then be stored and transmitted. It does so by sampling an analog audio signal aat regular intervals and quantizing each sample into a digital value. This is used in CDs, DVDs and Blu-ray discs among many applications.

PCM can be used with various bit depths and sampling rates.

What is the LPCM Audio Format?

LPCM is a form of PCM that is linearly quantized. LPCM (linear pulse-code modulation) is an audio technology typically found in digital audio applications.

Similar to PCM in that it converts analog signals to digital format, but uses different quantization techniques: linear quantization allows for splitting up an analogue signal into fixed levels represented by binary codes. The analog audio signal is sampled at regular intervals, and each sample is quantized with equal precision.

This method is often used for DVDs or Blu-ray discs.

The Differences Between LPCM And PCM

Quantization

One of the main differences between LPCM and PCM lies in their respective quantization methods. PCM generally refers to several quantization methods that includes non-linear methods of quantization.

On the other hand, LPCM utilizes linear quantization; as such, resolution in LPCM remains uniform across its entire dynamic range whereas resolution for PCM increases as its frequency range goes lower and vice versa.

However, the fact that PCM uses linear quantization means that a more accurate representation of the original analog signal is maintained, leading to higher audio fidelity.

Bit Depth

Both LPCM and PCM differ when it comes to how many bits are used to represent each sample; typically 16 or 24 bits for an LPCM signal and 8-16-24-32 bit depths in PCM samples respectively. Bit depth determines dynamic range; higher bit depths allow for increased dynamic range.

Compression

PCM audio data can often be compressed using lossless or lossy compression methods like FLAC or MP3. On the contrary, LPCM usually does not undergo compression because its usage often relies on professional applications where lossless audio quality is preferred.

Compatibility

PCM is more widely adopted as an audio format than its LPCM counterpart; it’s widely supported across consumer and professional applications including CDs, DVDs, Blu-ray discs and digital files. On the contrary, LPCM tends to be reserved primarily for professional applications while less commonly supported among consumer devices.

File Size

Because LPCM files do not compress as easily, their file sizes tend to be significantly bigger compared to PCM. This can present challenges when it comes to storing or transmitting audio data – larger file sizes occupy more storage space and increase transfer times.

Frequency Response

Both LPCM and PCM differ when it comes to frequency response; with the former possessing higher response (maximum sampling rate 192kHz versus PCM’s maximum of 96kHz). As such, LPCM may be better suited for applications that demand high-frequency responses such as audio production where quality audio performance is paramount.

Error Correction

PCM audio data often features error correction codes that detect and correct for discrepancies within audio data streams, while LPCM typically does not. This is likely because professional audio applications usually assume error-free transmission of their signal when employing this format.

Signal-to-Noise Ratio

Signal-to-noise Ratio (SNR) measures audio signal quality relative to background noise levels. Due to LPCM’s higher bit depth and linear quantization method, its SNR tends to be greater – meaning higher quality audio with reduced background noise levels can be delivered through it.

Dynamic Range

Dynamic range refers to the difference between the loudest and quietest parts of an audio signal, measured from the loudest to quietest points on either end of its frequency range. Due to LPCM’s higher bit depth and linear quantization method, its dynamic range tends to be greater.

This enables it to capture and reproduce more dynamic audio samples – perfect for high-quality applications where dynamic range matters such as mobile audio apps where dynamic range plays an essential part.

Conclusion

LPCM and PCM are two commonly-used formats for representing digital audio signals, yet each offers distinct benefits in different audio applications. Although their similarities overlap, there are notable distinctions that can affect which format best serves particular tasks.

For instance, LPCM is often chosen when high-quality lossless audio is needed while PCM supports more consumer devices and may allow compression for smaller file sizes. By understanding their distinctions more fully audio professionals can select an optimal format suited for their specific task.