While configuring the sound section of our new TVs, consoles, physical media players and streaming, you have surely come across a section where I put something like: “Bitstream, Passthrough, PCM or Decode audio output”.
The first two terms refer to the same notion of direct passage of the sound signal, without modifying or altering it in any way and with its original encoding and format. For example, if we have a Dolby Digital or Dolby Atmos track, we will send it as it is stored on optical media or as it comes from streaming, with its original number of channels.
The other two terms (PCM and Decode), although they are not identical, also refer in this context to the same concept of decoding the soundtrack to send it later in PCM format to the system which will play it. This ensures compatibility, as it will be played smoothly by any team, but we will be limited to stereo or 2.0 sound. Which is better, how do I configure my equipment to have the best sound quality?
Next we will see the most common use cases, but I already tell you that in general, as long as we have an external sound system, it is convenient to use the “Bitstream” also called by many manufacturers like “Passthrough” or “Direct pass”, because it is the only one that allows us to extract the multichannel audio signal without touching it or modifying it in any way so that it can be decoded by the soundbar , amplifier, receiver or television. But let’s go in parts.
From external players and consoles to television
The most common case is that we have external players or consoles connected to the TV and want to configure the audio output in them. If our television can decode the formats that we are going to send to it, then it is convenient that we use Bitstream.
This will generally be possible in some of the more advanced models on the market, a feature that we can consult in each specific instruction manual to find out if they are compatible with Dolby Digital, DTS, Dolby Atmos, etc.
However, the trend in recent years has occurred as some TV manufacturers maintain their commitment to compatibility with Dolby Digital and its developments, but have abandoned the possibility of working with formats derived from DTS, such as DTS-Master. Audio and of course DTS: X, which will not allow us to send audio in direct pass mode.
Therefore, if our TV does not support decoding of these formats, then we need to make the sound signal from the already decoded player or console to PCM format, thus having stereo or 2.0 sound that the TV will be able to interpret and reproduce through sound speakers.
In this case, we logically lose the surround audio capabilities, even if we can continue to apply the equalizations and digital processing offered by the operating system of our screen thereafter.
From TV to sound bars and AV receivers
In case we want to transfer the sound from the TV to an external sound system such as a sound bar or a home theater set, either via digital optical connector, coaxial or via HDMI with ARC, we are interested in sending the sound without altering it in any way.
What suits us therefore is to select the direct pass or Bitstream so that the sound material is responsible for capturing the audio signal, decoding it, processing it in general more efficiently than the TV would do, and later. to distribute it among your connected speakers for true multi-channel sound.
From players and consoles to an AV receiver or soundbars
If you have different equipment such as consoles or portable players connected to an AV receiver and then to the television, it is also practical to select sending in direct or Bitstream mode.
The idea is the same as in the previous case. We send the sound intact to the audio system, which will decode and process the signal to provide the best quality.
A special case occurs when the players and consoles are connected to an AV receiver and from there we transmit the sound signal to the TV via an HDMI ARC or eARC cable. In these cases, if the receiver is moderately modern, we can configure it to transmit the audio and video signal directly to the TV so that we can see and listen to the content of these players and consoles on the TV without having to turn on the receiver, both that we have it in standby mode connected to an electrical outlet.
This can be useful if, for example, we want to use the receiver only to output the sound of certain games and movies, but not for other uses such as watching videos from streaming sources, playing trailers, etc.