PCM or Bitstream on Your TV

The Two Output Formats

With PCM, the sound is already decoded in the source device and output as an audio signal. With Bitstream, the encoded data stream is passed to the next device, such as a soundbar or an AV receiver. Which setting is appropriate therefore depends on which device should handle further processing.

PCM

PCM stands for Pulse Code Modulation. The sound is transmitted as a long sequence of measured values, without compression. In the menu, the setting appears as PCM, LPCM, or Linear PCM. These all refer to the same format.

If the audio output is set to PCM, the TV or player decodes the sound itself and passes on the finished audio signal. The connected device does not need to support a specific audio format for this. PCM therefore works with most soundbars, AV receivers, and stereo systems.

Bitstream

With Bitstream, the source device passes on the sound as it is present in the broadcast or on the Blu-ray, for example, in Dolby Digital or DTS. The data stream remains encoded and is only decoded in the soundbar or AV receiver. However, some TVs convert individual formats along the way, for example, to Dolby Digital, if the connection cannot transmit the original.

For this, the connected device needs a suitable decoder. If it is not present, there will be no sound or only static will be heard. Some devices also refer to this setting as Passthrough.

The Question of Sound Quality

In both cases, the sound is decoded; the only difference lies in the device that performs this task. Afterward, it is always available as PCM before being converted into an audible signal.

Each audio format precisely dictates how a data stream becomes an audio signal again. Therefore, the TV and soundbar will achieve the same result, as long as both fully support the format. Which device decodes makes no difference to the sound quality. Differences are more likely to arise if channels are lost along the way or if a device handles volume and dynamics differently.

Compression and Sound Quality

With PCM, the sound is transmitted uncompressed, meaning no data is saved. This initially sounds like better quality. However, this is only true if the audio track was fully available beforehand. Most audio tracks from TV broadcasters and streaming services are already compressed by the provider, for example, in Dolby Digital. This removes components that are barely noticeable when listening. If the TV decodes such an audio track and passes it on as PCM, these components do not return. The data volume increases, but the sound remains the same.

Conversely, Bitstream does not necessarily mean a loss of quality. Audio formats include lossy and lossless variants. Dolby Digital and DTS save data by omitting hard-to-hear components. Dolby TrueHD and DTS-HD Master Audio, found on many Blu-rays, only compress the sound to save space, similar to a ZIP file on a computer. After decoding, it is exactly as it was during mixing in the studio. These formats are also transmitted as Bitstream but require eARC or a direct HDMI connection between the player and AV receiver.

PCM or Bitstream Depending on Setup

Whether PCM or Bitstream should be set depends on which devices are connected to the TV and how they are connected. For the built-in speakers, the selection usually doesn’t matter much. For a soundbar or an AV receiver, however, it does play a role and can determine whether multi-channel sound works.

The recommendation depends on whether the connected device can decode the audio format itself and whether the connection transmits multi-channel sound as PCM.

TVs Without External Speakers

If the sound is played through the built-in speakers, the setting usually has no effect. It applies to the digital audio output, i.e., the optical jack and the HDMI port with ARC. The same applies to Bluetooth headphones, as the TV decodes the sound itself for them anyway.

Soundbar or AV Receiver Connected to the TV

If a multi-channel soundbar or an AV receiver is connected, Bitstream is better in most cases. This is the only way for multi-channel sound like 5.1 to reach the device via the optical connection or HDMI ARC. If PCM is set instead, the TV downmixes the sound to stereo via these paths.

It’s different if both the TV and the audio device support eARC. In that case, multi-channel sound also arrives with PCM. The selection is less critical in this scenario. However, if the audio device is to process formats like Dolby Atmos itself, Bitstream is still necessary.

DVD Player and Game Console

The same selection is available on DVD and Blu-ray players, streaming boxes, and game consoles. If these are connected directly to a soundbar or AV receiver, the same rules apply as for the TV. If they run through the TV, the setting must match the entire setup. If the TV cannot pass on a format, it often converts it to stereo PCM or Dolby Digital.

Older Devices and Stereo Systems

Older AV receivers and simple stereo systems often cannot decode newer audio formats. Therefore, PCM is the better option here. The device then receives an already decoded audio signal and does not need to know the format itself. With a pure stereo system, nothing is lost, as it only reproduces two channels anyway.

Number of Channels Depending on Connection

The connection determines which setting must be made on the TV. The optical output and HDMI ARC transmit PCM with only two channels and multi-channel sound only compressed as Bitstream. This means they have narrower limits than eARC, which can also transmit uncompressed multi-channel sound and the lossless audio tracks of a Blu-ray.

Optical Output and ARC

Via the optical output and HDMI ARC, PCM can only be transmitted with two channels. Multi-channel sound is transmitted there only in compressed form, i.e., as Bitstream in formats like Dolby Digital or DTS. The lossless audio tracks of a Blu-ray do not arrive via these paths.

Anyone who has connected a 5.1 soundbar via one of these connections therefore needs Bitstream to use multi-channel sound. With PCM, the sound will arrive, but only in stereo.

eARC

eARC allows multi-channel sound to be transmitted uncompressed as PCM, as well as lossless formats like Dolby TrueHD or DTS-HD Master Audio. Both settings can therefore transmit all channels. The prerequisite is that both the TV and the audio device support eARC and a suitable HDMI cable is used.

Find and Check the Setting

In the menus, there are different names for this setting depending on the device. Whether it works can then be easily checked. Simply play a movie with multi-channel sound and take a look at the audio device.

The Setting in the Menu

On the TV, you need to navigate to the sound settings and look under the Expert Settings or Sound Output section. There, the item might be called Digital Audio Output, Audio Format, or Digital Audio Out. On Blu-ray players and game consoles, the setting is found in the system’s audio or sound settings.

Some devices also differentiate between the optical output and HDMI. In that case, the setting must be changed for the connection to which the audio device is actually connected.

Checking on Soundbar and AV Receiver

Many soundbars and AV receivers indicate which format is currently being received, either on the display or via an indicator light. For a movie with 5.1 sound, the respective format, such as Dolby Digital, should appear there when Bitstream is selected. If only PCM or Stereo is displayed with an optical connection or ARC, the sound was downmixed to two channels along the way. Via eARC, however, PCM can also mean multi-channel sound.

Offset Between Picture and Sound

Decoding in the soundbar or AV receiver takes a short moment. After switching from PCM to Bitstream, it can therefore happen that lip movements no longer quite match the sound. The sound then comes a little later than the picture.

The audio delay setting offered by many TVs and soundbars usually doesn’t help in this case. It generally only outputs the sound later, not earlier. If it’s already too late, the offset will only increase.

In practice, it often helps to restart the devices in the correct order. To do this, turn off the TV and soundbar or AV receiver, then turn on the audio device first, and only then the TV. When turning on, the TV learns via HDMI which formats the audio device processes and how long it takes. Many TVs then delay the picture themselves to match the sound.

Effects of the Setting

In addition to the number of channels, the setting determines which device processes the sound further. Depending on the selection, sound settings such as night mode must then be made on the TV or the soundbar. Many TVs and players also have an automatic setting that makes the selection independently.

Night Mode and Volume

With PCM, the TV processes the sound before passing it on. Depending on the TV, settings like night mode or automatic volume then also affect the sound that reaches the soundbar. However, sound mode and equalizer are often locked for external audio output. With Bitstream, the TV passes on the sound unprocessed, so the settings of the soundbar or AV receiver usually apply.

Formats like Dolby Digital also contain additional information on volume and dynamics. These are evaluated by the device that decodes the sound. If the volume changes significantly when switching between channels or apps, trying the other setting can help.

Automatic Setting and Menu Labels

Many devices offer an ‘Auto’ setting in addition to PCM and Bitstream. Via HDMI, the soundbar informs the TV which audio formats it can process. The automatic setting is based on this feedback. However, it is missing for the optical connection, as the TV does not know the soundbar’s capabilities there. In this case, it is better to manually select PCM or Bitstream.

Some menus name the format directly instead of Bitstream, for example, Dolby Digital.