PCM vs Auto in TVs – All You Need to Know

When setting up your TV, it’s important to select the best audio output format for your setup. You may be using headphones, TV speakers, external speakers, or a home theater setup. The two most common audio output formats in any TV are PCM and Auto, but choosing between these two can be tricky.

PCM is better if you’re using the TV speakers. The Auto setting usually uses Dolby Digital 5.1 sound, making it better for external speakers, home theater setups, or other surround sound systems.

In the rest of this article, I will explain when to use PCM vs. Auto, each of these sound formats, and how to select different audio output formats on your TV. Let’s get into it.

Also read: PCM vs Dolby Digital vs Passthrough – Key Differences

PCM vs Auto in TVs

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PCM, in TVs, is usually a PCM 2.0 track, which means the uncompressed audio is sent through a two-channel track. In most TVs, Auto refers to a surround sound output, wherein the audio is compressed into a Dolby Digital format and sent through multiple channels.

PCM is better for TV speakers, while Auto is better for external speakers or home theater setups. PCM sends uncompressed audio in the stereo (two-channel) track, while Auto generally uses Dolby Digital tracks, wherein the audio is compressed and sent through a multi-channel track.

The kind of audio output required depends on the sound setup you have at home. Let’s look at a few common setups and which kind of output would be best for each case. Here is a comparison:

FeaturePCM (Pulse Code Modulation)Auto
DefinitionAn uncompressed digital audio format that encodes analog audio signals into digital form.A setting that allows the TV to automatically select the appropriate audio format based on the input signal.
CompatibilityCompatible with all audio devices, as it is a basic and widely supported audio format.Compatibility depends on the input signal and the TV’s ability to recognize and process the audio format.
Audio QualityUncompressed audio, providing high audio quality but larger file sizes.Audio quality depends on the input signal and the audio format chosen by the TV. Can range from uncompressed to various compressed formats.
Surround Sound SupportPCM can support up to 7.1 channels of audio, but most TVs only support 2-channel (stereo) PCM.Supports a variety of audio formats, including multi-channel surround sound, depending on the input signal and the TV’s capabilities.
Ease of UseNo need to configure settings, as PCM is a universally supported format. May not provide the best experience for surround sound setups.Automatically selects the best audio format, simplifying the user experience. Can provide a better experience for surround sound setups if the TV supports advanced audio formats.

TV Speakers

Most TVs come with a speaker built-in. However, these speakers are quite small, and they keep getting smaller in newer models. However, you may feel like your TV setup does not require additional external speakers. 

So, which output audio should you use for the regular TV speakers? This will usually depend on the TV brand (more on that later on), but PCM output is generally advised for TV speakers.

The biggest advantage of PCM is that the audio signal sent to the audio receiver is uncompressed. Uncompressed audio eliminates the usual problems of low volume or unclear sounds in the general Auto output. Because of the small size of the TV speakers, this type of audio signal is ideal.

2.0 Or 2.1 Sound Systems

Let me quickly explain what a 2.0 or 2.1 sound system is.

A 2.0 or 2.1 sound system refers to the number of channels in which the audio signal is mixed and how those are outputted to the receiving device.

2.0 refers to the normal stereo setup with a “left” channel and a “right” channel. Speaker setups using this kind of audio will only have two speakers on the left and right sides of the TV.

2.1 is similar to 2.0, except it also has a subwoofer (a speaker specifically designed to reproduce low bass sounds). This subwoofer is the “.1” in speaker setups because it does not have its own channel but takes up roughly a tenth of the frequency of the regular channels. 

In a 2.1 audio output, the .1 comes from a Low Frequently Effects (LFE) channel, which is reproduced by the subwoofer. However, a subwoofer is not always necessary, as even regular bass speakers can often reproduce the same sounds.

For 2.0 or 2.1 audio output, PCM is better. Generally, PCM output in TVs is capable of only stereo (two-channel) output, so it is wasted on a surround sound system. However, the uncompressed audio signal makes it ideal for a regular, front-facing speaker setup because no volume or audio quality is lost.

5.1 Sound Systems

5.1 sound is the main audio output used for surround sound systems. The 5 in this refers to the number of audio channels that the audio signals are mixed in. Similar to the previous example, the .1 stands for the LFE channel or the low bass sounds from a subwoofer. The five audio channels in a 5.1 system are as follows.

  • Front Left
  • Front Right
  • Front Center
  • Surround Right
  • Surround Left

These five channels correspond to the position of the audio locations relative to the visual output. These locations also refer to the placement of the five speakers in the room, which are explained below.

  • The Front Center speaker is placed directly in front of the viewer.
  • The Front Left and Front Right speakers are usually placed on the respective sides of the Front Center speaker, set at a 30° angle from the viewer.
  • The two Surround speakers are placed at the left and right side of the viewer, at an angle of 110°.
  • All speakers should ideally be equally distanced from the viewer.

Auto settings are the best for this kind of surround setup because they usually use multi-channel outputs that are designed for a surround sound experience. In some TVs, you might even see different Auto options like Auto1 or Auto2 –these generally refer to either Dolby Digital or Dolby Atmos. You will have to check your user manual or contact the manufacturer to find out which options your TV has.

PCM is generally not advised for 5.1 systems because most TVs lack the PCM settings necessary for multi-channel surround sound. 

7.1 Sound Systems

7.1 systems are the highest options available in most TVs, although a few newer models may offer support for 9.1 or even 11.1 surround sound. As the name suggests, 7.1 refers to seven audio channels and one LFE channel for the subwoofer.

The seven audio channels in a 7.1 system are:

  • Front Left.
  • Front Right.
  • Front Center.
  • Surround Left.
  • Surround Right.
  • Left Rear Surround.
  • Right Rear Surround.

As with the other options, there is also a subwoofer for the low bass sounds.

This setup is usually considered the ideal home theater system, although a 5.1 system can also be considered a home theater. The speaker placements in the 7.1 are identical to the placements in the 5.1. The only addition here is the Rear Surround speakers, which are placed behind the viewer at the left and right corners of the setup.

Auto is the better option for this system because of its surround sound capabilities. PCM would not work well on this setup because of the lack of multi-channel output.

Recommended Audio Output for Different TVs

Below is a quick summary of the recommended audio output for four of the most common TV brands.

5.1Dolby Digital/Digital DTSDolby Digital/AutoAutoAuto

Note: Dolby Digital is often the same as the Auto option in some TVs. Check your user manual to find out how the option has been named in your TV.

In general, most brands recommend PCM for 2.0 or 2.1 systems, while Auto is recommended for surround sound. Many TVs cannot produce seven-channel tracks, but users have reported that the five-channel tracks work well enough even with a 7.1 setup.

Final Thoughts

Most TVs have two main audio output settings – PCM and Auto. Auto is usually the default setting on the TV and often uses Dolby Digital tracks.

The kind of output selected depends on your speaker setup and personal preference. For 2.0 or 2.1 setups, PCM is the more recommended output because the uncompressed audio results in no loss of data. But for 5.1 setups or higher, Auto is recommended because of its multi-channel capabilities.

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