Introduction To The PCM vs Bitstream Discussion
In this update, we can certify that for the users, there is practically no noticeable difference in quality between PCM and Bitstream (1) (2). We will discuss below the evidence that we have to demonstrate it (3) (4). Likewise, we will also mention a few cases where the PCM vs Bitstream discussion has relevance (5) (6) and you should care about it (7) (8).
Players (we include Blu-ray players or any kind of player) have various options for audio and video output settings, depending on how the player is physically connected to the AV receiver (10).
If you have your player connected to the AV receiver via HDMI, there are 2 main audio output settings available: Bitstream and PCM (9).
In terms of the actual audio quality, whether you have the audio output configured via HDMI to PCM or Bitstream is not important (11).
In terms of the actual audio quality, whether you have the audio output configured via HDMI to PCM or Bitstream is not important.
For audio, if you connect your Blu-ray Disc player to your home theater receiver via HDMI, there are two main audio output settings available: Bitstream and PCM (similar to LPCM, but not the same thing). In terms of actual audio quality, it does not matter if the HDMI audio output from your Blu-ray Disc player is set to PCM or Bitstream.
PCM gets the sound directly from your console without having to go through a home theater to get it right. For me, PCM is for those who do not use speakers or play with headphones. This is my personal view and I do not have actual evidence retrieved.
Without speakers, the DTS and Dolby option will sound looser than PCM losing quality in the volume and smaller sounds.
When it comes to setting up an audio system, in the discussion PCM vs Bitstream, people often confuse LPCM and PCM with Bitstream. Others still do not know which option to choose or which is best for them.
PCM Vs Bitstream: The Bottom Line
PCM And Bitstream At A Glance
For audio, if you connect a device (Blu-ray Disc player, Ultra HD Blu-ray disc players or other similar devices) to a home theater receiver via HDMI, there are two main audio output settings available: Bitstream vsPCM (which is similar, but not equal, to LPCM).
In terms of sound quality, whether you set the device (Blu-ray Disc player or another device) HDMI audio output PCM or Bitstream does not matter, generally speaking. However, here is what happens when you choose either setting.
If you set the Blu-ray Disc player to output audio as PCM, the player performs the audio decoding of all Dolby/Dolby TrueHD and DTS/DTS-HD Master Audio related soundtracks internally. Then, it sends the decoded audio signal in an uncompressed form to the home theater receiver.
As a result, the home theater receiver will not perform additional audio decoding before the audio is sent through the amplifier section and the speakers. With this option, the home theater receiver displays the term PCM or LPCM on its front panel display.
If you plan to use the secondary audio feature, which provides access to audio commentaries, descriptive audio, and supplementary audio tracks, use PCM. When access to these audio programs is important to you, set the Blu-ray player to PCM to provide the best quality result. The player decodes the audio, without bandwidth concern, which is an issue for bitstream.
For digital optical and coaxial connections, while the bitstream output option can send a standard Dolby Digital or DTS 5.1 surround sound signal to a receiver for decoding, the PCM option sends a two-channel signal. A digital optical or digital coaxial cable does not have sufficient bandwidth capacity to transfer a decoded, uncompressed, full surround audio signal like an HDMI connection can.
If you select Bitstream as the HDMI audio output setting for a Blu-ray player, the player bypasses its internal Dolby and DTS audio decoders and sends the undecoded signal to your HDMI-connected home theater receiver. The home theater receiver does the audio decoding of the incoming signal. As a result, the receiver will display Dolby, Dolby TrueHD, DTS, DTS-HD Master Audio, Dolby Atmos, DTS:X, or another format on its front panel display depending on which type of bitstream signal is decoded.
If you combine the bitstream and secondary audio settings, the Blu-ray Disc player will down-res surround formats, such as Dolby TrueHD or DTS-HD, to standard Dolby Digital or DTS to squeeze both types of audio signals into the same bitstream bandwidth. In this case, the home theater receiver recognizes the signal as standard Dolby Digital and decodes appropriately.
Difference Between PCM And Bitstream At A Glance
The difference between PCM and Bitstream is in regards to the device utilized for decoding the compressed format to retrieve the uncompressed PCM data. If you utilize Bitstream, then the AV receiver is performing the decode. PCM is not better than Bitstream format in terms of quality. The Bitstream package is where the PCM data was sourced from.
Aside from sound quality, there is one reason to prefer sending PCM over Bitstream—secondary audio. On most Blu-rays, there are audio elements in addition to the main soundtrack—specifically, the audio that accompanies PIP (picture-in-picture) commentaries and the sounds that onscreen buttons make when you click on them. If you set the player to send Bitstream, you will not hear this secondary audio, but if you set it to send PCM, the secondary audio is mixed with the main soundtrack so you can hear it.
PCM Pros And Cons
- Better quality access to additional audio tracks.
- Quicker, direct, and eliminates lag.
- Less work for the receiver.
- Decoding is done in the player (Blu-ray player or any player device).
- PCM transmits a two-channel signal over digital optical or coaxial.
- Audio quality is partially determined by the player (Blu-ray player or any player).
- More work is done by the player.
Bitstream Pros And Cons
- Bitstream sends an encoded 5.1 signal over digital optical or coaxial.
- Possibility of higher quality sound.
- If the receiver offers higher quality audio processing, it can be used.
- The home receiver decodes audio.
- Supplemental audio is scaled down, which decreases quality.
- It requires a high-quality receiver to achieve better results.
- More work is placed on the receiver.
The PCM Option
To continue with this PCM vs Bitstream discussion, let´s see a practical setting in PCM.
If you set your Blu-ray Disc player to output audio as PCM, the player will perform audio decoding of all Dolby/Dolby TrueHD and DTS/DTS-HD Master Audio related soundtracks internally and send the decoded audio signal in uncompressed form to the home theater receiver.
As a result, your home theater receiver will not have to do any additional audio decoding before the audio is sent through the amplifier and speaker section. With this option, your home theater receiver will display “PCM” or “LPCM” on the front panel display.
This means that if you set the audio output of your Blu-ray player to PCM, the player will decode the audio of all Dolby/Dolby TrueHD and DTS/DTS-HD Master Audio formats – from the internally related soundtracks and send the audio signal in an uncompressed form to the AV receiver in your home theater.
As a result, the AV receiver will not have to perform any additional audio decoding before it is sent to the amplifier section and speakers.
This type of connection is available on most CD players.
With this option, the home theater receiver will display the PCM term on its front panel display.
The Bitstream Option
If you select Bitstream as your HDMI audio output setting from your Blu-ray player, the player will bypass its internal Dolby and DTS audio decoder and send the signal without decoding to the AV receiver connected to the HDMI.
Then, if the user decides to use Bitstream as the HDMI audio output setting for their Blu-ray player, the player will bypass its own internal Dolby and DTS audio decoders and send the signal without decoding to their HDMI-connected home theater receiver. The home theater receiver will do all the audio decoding of the incoming signal. As a result, the receiver will display Dolby, Dolby TrueHD, DTS, DTS-HD Master Audio, Dolby Atmos, DTS:X, etc…on its front panel display, depending on the type of bitstream signal being decoded.
With this setting, the AV receiver will do all the audio decoding of the incoming signal.
As a result, in this case, the AV receiver will display on its main display the tags Dolby, Dolby TrueHD, DTS, DTS-HD Master Audio, Dolby Atmos, DTS:X, etc… depending on what type of Bitstream signal is being decoded.
It should be noted that the Dolby Atmos and DTS:X surround formats are only available from a Blu-Ray player via the Bitstream option. There is currently no Blu-ray player that can decode these formats internally for PCM and pass them on to the Home Theater receiver, which in part finishes this PCM vs Bitstream confrontation.
You have the option to choose which type of setting to use (PCM vs Bitstream), and as mentioned above, each setting should produce the same audio quality, taking into account the exceptions of Dolby Atmos and DTS:X.
Setting the Secondary Audio
There is another factor to consider for this PCM vs Bitstream study: Secondary Audio. This function provides access to audio comments, descriptive audio or other supplementary audio tracks. If access to these audio programs is important to you, keeping your Blu-ray player set to PCM will provide the best quality result. This means that an additional setting option that may be available on your Blu-ray player is “BD-Secondary Audio”.
If you combine the bitstream and secondary audio settings, the Blu-ray Disc player will “downstream” the surround sound formats, such as Dolby TrueHD or DTS-HD, to standard Dolby Digital or DTS so that both types of audio signals can be compressed into the same bitstream bandwidth. In this case, your home theater receiver will recognize the signal as Dolby Digital standard and decode it properly.
Therefore, using this setting the user combines the primary high-resolution audio signal (Dolby TrueHD or DTS-HD Master Audio) with the secondary audio signal – however, if you use this setting, the Blu-ray player will lower the resolution from Dolby TrueHD or DTS-HD to Dolby Digital standard or DTS in order to be able to input both types of audio signals in the same bitstream.
HDMI vs. Digital Optical/Coaxial Connections
After you determine the audio settings you want to use to transfer audio from your Blu-ray player to the rest of your home theater system, you must also decide what type of connections to use. So after you can determine which audio settings you want to use to transfer audio from your Blu-ray Disc player to the rest of your home theater system, you must also decide what type of connections you need to use.
If you use either the coaxial or optical digital connection option of your Blu-ray player to your home theater receiver (very useful if your AV receiver does not have HDMI connections), you can also select the PCM vs Bitstream output options for those connections.
However, in this case, while the Bitstream output option can send a Dolby Digital or DTS 5.1 surround sound signal to your receiver for later decoding, the PCM option will only send a 2-channel signal.
The reason for this is that the optical digital cable or coaxial cable does not have sufficient bandwidth capacity to transfer a decoded, uncompressed, full surround sound signal, as the HDMI connection can.
If you are using the optical digital or coaxial digital connection option from your Blu-ray Disc player to your home theater receiver (useful if your home theater receiver does not have HDMI connections), you can also select PCM vs Bitstream output options for those connections.
However, in this case, whereas the Bitstream output option can send a standard Dolby Digital or DTS 5.1 surround sound signal to your receiver for later decoding, the PCM option will only send a two-channel signal. The reason for this is that a digital optical or coaxial digital cable does not have sufficient bandwidth capacity to transfer a decoded, uncompressed, fully surround audio signal as an HDMI connection can.
It should also be noted that optical/coaxial digital cables cannot transfer Dolby Digital Plus, Dolby TrueHD or DTS-HD Master Audio as a bitstream or PCM – HDMI is required.
Although the above discussion focuses on PCM vs Bitstream with respect to Blu-ray Disc players, the same information may also apply to Ultra HD Blu-ray Disc players.
Similarities Between Bitstream And PCM
While Bitstream and PCM are very different, these two configurations are very similar when applied in audio production. Here are several similarities to consider when choosing which is the best option for you:
- Both have great sound quality
- You can play both Bitstream and PCM files on most DVD and Blu-Ray players.
- Both signals must be converted into analog form to be heard through the speakers.
PCM and Bitstream: Main Differences
- PCM (pulse code modulation) is the “raw” signal generated by the AD converter. This means that the signal is not additionally source-coded by, for example, DTS or Dolby Digital, and is therefore not converted.
- As PCM, your signal is pure and usually in the highest quality. It takes up a lot of space but sounds very good.
- There are also formats such as Dolby Digital or DTS where the signal is (source-)encoded. In these two examples, the encoding is done with a loss of quality.
- However, there are also lossless compression methods such as DTS-HD Master Audio or Dolby TrueHD.
- These formats are transmitted in so-called bitstreams. Here you can choose whether, for example, your Bluray player or your AV receiver should do the decoding work. Note: If your receiver takes over the decoding, the corresponding logo usually appears on the display.
- The advantage of this is that the audio track can be compressed and stored on your Bluray, but you still get the highest quality in the end. Because the pure PCM signal can be recovered from the DTS-HD Master Audio track.
- The disadvantage of this is that your receiver must also support this decoding procedure. In this case, you can simply let your player decode the signal and output it as PCM and not as bitstream.
- This also means that your receiver does not necessarily have to support the new HD formats to play you back in full quality.
Which Option Is More Convenient For You
However, there is another factor to consider as to which setting may be best for you to decide in this discussion PCM vs Bitstream.
This involves access to secondary soundtracks, such as audio commentary, descriptive audio, or other supplementary audio tracks.
If access to these audio features is important to you then keep your Blu-ray player configured with the PCM audio output option that would be the best choice for you.
Alternatively, you can always switch from PCM to Bitstream at any time by going to the appropriate settings menu.
Final Verdict: PCM Vs Bitstream
While audio signals are produced differently in both cases, there is no audible difference between Bitstream and PCM files. However, the Bitstream files are encoded to give you a surround sound experience when used with a compatible media player.
On the other hand, most audio players only support the PCM format while transmitting sound. That means you should check the compatibility of your device when choosing between the two.
HDMI is easily the best option for output. However, if you use either digital or optical coaxial outputs, Bitstream is the clear winner. Digital optical and coaxial connections suffer from limited bandwidth and can’t transfer a fully-processed and decoded signal. Because bitstream relies on the receiver for decoding, it’s ideal for limited bandwidth situations.
There are a number of factors that should go into your choice, including the quality of your Blu-ray player and audio receiver. More often than not, you will want Bitstream. The potential for greater audio quality and the flexibility to use coaxial outputs puts it ahead of PCM.
The only situation where PCM comes out on top is when using secondary audio streams. If you do not plan on doing this, and your receiver is not severely lacking in quality, go for Bitstream.
What is PCM: Pulse Code Modulation
PCM is an algorithm for representing an analog wave digitally and has been around since the beginning of the 1900s. This is not the only algorithm out there, there’s pulse width modulation, pulse position, pulse density, delta-sigma (which is used with DSD), and others but PCM is by far the standard (for audio). PCM itself comes in a couple of flavors, regular PCM where quantization levels is a function of amplitude and LPCM where quantization levels are uniformly linear (hence linear pulse code modulation).
Since PCM is an algorithm, compressed/noncompressed doesn’t make any sense from a technical standpoint, it takes an input and gives you an output and doesn’t care what the data is.
Because this is the standard (for audio), pretty much everything uses it AVR, pre/pro, stereo receiver, sound cards/onboard sound, pretty much everything that deals with converting digital to audio (and audio to digital) uses PCM at the bottom of the chain.
But like a lot of things, it takes on new meanings though it is not necessarily correct in the strictest sense, in this instance many people also include the digital output as just “PCM” also.
Well, it is just a data file you can call it PCM data file but when it is just referred to as PCM misunderstandings happen (and the thing you have to understand is that going from analog to digital is not 1 to 1, going from digital to analog is though so in a broad general sense PCM is a lossy compression algorithm itself). That data file is not very useful unless you know the parameters used by the PCM encoding so we use headers and containers for streaming/storage.
Wav, AIFF, FLAC, Ogg, mp3, DD, DTS, etc are all containers, some happen to be more than just that such as FLAC, MPEG, DD, DTS (and others) which are also a compression algorithm(some lossy, some lossless) and/or encoding scheme. When you play any of these formats, they all are converted to PCM data for the DAC to use. Yes, I know, you see chips that include DD/DTS decoding and they do that, but it is still a conversion to PCM data first before converting to analog.
Pulse Code Modulation, the coded data stream that occurs when analog audio information is converted into digital signals. In the PCM data stream of the CD, the sampling rate is 44.1 kHz, i.e. during one second, the analog signal is sampled 44,100 times and converted into a digital value. For Dolby Digital the sampling frequency is 48 kHz, for DVD-Audio 96 kHz. The quantization (also called resolution) indicates how many different digital values a signal can be converted into. 16-bit word width is standard for the CD. This allows 65,556 different audio information to be represented.
In the DVD-Audio standard, the resolution is 24 bit. This allows 16.77 million different pieces of information to be displayed, which is 256 times the fine resolution of the standard CD.
Linear Pulse Code Modulation = the uncompressed, linear PCM sound contained on the DVD. LPCM can be stored in different quantization or resolutions (16 bit, 20 bit or 24 bit) and in different sampling rates or sampling frequencies (48 kHz or 96 kHz).
PCM And LPCM Differences
Normal PCM, as in the audio CD sector, transmits up to two channels. LPCM can transmit up to eight channels.
Please do not lump PCM and LPCM together, even though they are both the same technology. MP2 is also not the same as MP3 even if they are the “same technology”. There are several recording modes with different resolutions (8, 12, 16, 20 and 24 bit) and different sampling rates (32kHz, 44.1kHz, 48kHz, 88.2kHz, and 96kHz) for LPCM.
Playstation Specific Case For Bitstream And PCM
This is the question that all owners of a home cinema system with an AV receiver and console like PS4 are asking themselves: PCM vs Bitstream? What that actually is and which setting delivers the better sound is revealed here.
Let us imagine the following setup: The PlayStation 4 is connected to the AV receiver via HDMI cable, the AV receiver is also connected to the television via HDMI and a 5.1 box set is connected to the AV receiver.
In the sound settings of the PS4, the user can now choose between Linear PCM and DTS (Bitstream) and Dolby Digital (Bitstream). If PCM is selected, the PS4 takes over the audio decoding of the sound material and passes it to the AV receiver, which usually outputs it to the speakers unchanged with the specified number of channels. So if the PCM signal is stereo, the only stereo will be output. If the signal is a 5.1 signal, 5.1 sound will also come out.
If the PS4 is set to bitstream – regardless of the audio technology, for example, DTS or Dolby Digital – the PS4 passes the unprocessed signal to the AV receiver, which then takes over the audio decoding. Provided it also supports the sound codec set on the PS4.
PCM is therefore merely a specification that controls which device is used for decoding. The choice depends on the quality of the individual devices – in this case on whether AV receivers or PS4s are better at decoding. In general, however, the AV receiver is usually the better choice.
After all, it is designed for such cases. PCM is best suited to those who do not have an AV receiver and output the sound via the TV boxes. This also calls for PCM: If you want to output HD sound formats such as Dolby True HD or DTS HD, but the AV receiver does not support them.