You might have bought a new audio system and then you find two options – Bitstream and PCM. You consider which is better than the other and what is the difference between them. Also, you don’t know if all your hardware is compatible with PCM or Bitstream. In this article, we will compare Bitstream vs PCM and discuss all the technical details you need to know about them before making your choice.
What is Bitstream?
Bitstream as the name suggests is a stream, series, or sequence of bits. Bits are the lowest lexical units used by electrical devices to communicate, store and process information. These are better known as ‘0’s and ‘1’s. Any information can be represented in a specific series of ‘0’s and ‘1’s. Here, ‘0’s and ‘1’s represent the voltage level. 0 is a low voltage and 1 is high voltage. Now, Bitstream is a technology that transfers audio by compressing it and then transmitting it in a variety of frequency bandwidths. When you have modern sound media players that support advanced audio formats such as various Dolby and DTS formats you should be using bitstream to transmit audio.
Bitstream is a newer technology and does not support backward compatibility so older devices won’t work with this technology. Also, it can transmit data over wired and wireless. The encoded audio by the transmitter is decoded by the receiver which results in audio lag. Using different audio codecs can minimize this lag but it won’t vanish away.
What is PCM?
PCM is the short form of Pulse Code Modulation. This is a method that converts analog audio to digital audio. It is an algorithm through which analog waves are represented. PCM is a very older technology as compared to the bitstream, it has been around for more than 100 years and also works today. PCM is a bit different than bitstream in terms of audio transmission and decoding. It does not compress audio so it requires a large bandwidth to transfer information because of which PCM can transmit only in wired mediums.
Because there are no compressions, you also don’t get any advanced audio format support for surround sound audio files. But this also has an advantage as it offers very minimum lag as compared to the bitstream. Also, there is LPCM which is Linear Pulse Code Modulation which is quite different from PCM. PCM transfers data in which quantization levels vary as a result of amplitude whereas in LPCM quantization levels are linearly uniform.
Bitstream vs PCM
Bitstream and PCM vary in various aspects and we will elaborate on all these aspects at different points. Also for your convenience, we have made a simple table for easily distinguishing between them.
|Compatible with modern devices that support surround sound or spatial sound and wireless transmission
|Compatible with most devices including all old devices such as CD, DVD, Blu-ray players, etc.
|Supports advanced Bluetooth codecs such as Qualcomm aptX, aptX HD, etc. Also supports advanced audio formats such as Dolby, DTS and other formats
|Only supports stereo channel and no advanced audio format
|Supports wired and wireless connection. Wired connection includes full compatibility of coaxial and digital optical cable and wireless medium comprises of Bluetooth, NFC and WIFI.
|Supports only wired medium but there is very less compatibility of coaxial and digital optical cables.
|Encoding is done at the source and decoding is done at the receiver’s end.
|No decoding is done at the receiver’s end and transmission of raw bits takes place
|No multichannel so no support for secondary audio
|Full support for secondary audio because multiple audio frequency waves can be transmitted at once
|Transmission takes time because encoding and decoding takes place which can cause audio lag
|Minimal audio lag because raw bits are passed so no decoding is necessary at the receiver’s end.
Compatibility plays a big role in whether you can use technology or not. Bitstream was made for modern audio devices which is why it supports only modern media players. It is responsible for transmitting advanced audio formats such as Dolby Digital, DTS:X, Dolby Atmos, Dolby TrueHD, DTS HD-Master, and other formats. Because these audio formats are fairly and didn’t exist before there was no technology made to transmit such formats. PCM is a very old technology, older than 100 years but it is still used today.
PCM is compatible with every media player. PCM does not support any advanced audio formats and only supports 2.1 channel as stereo. This is why it is not preferred for modern media players. Also, you have to check whether your device supports any advanced format, in that case, check the transmitter, for example, your phone, laptop, or TV and then check your receiver such as your headphone, speaker, or home theatre. If both devices have support for advanced audio formats, then only you can use bitstream otherwise you won’t have any options and you have to choose only PCM.
There is no noticeable difference in sound quality. Bitstream might sometimes have a degraded sound quality because bitstream has to compress the audio file before transmitting and then again decompress the audio file after transmitting, this process of encoding and decoding continuously can result in some degradation in the audio quality, especially when using a wireless transmission medium. Also, if you have connected your device over Bluetooth support for advanced audio codecs such as Qualcomm aptX, aptX HD, etc will increase the audio quality drastically.
Now, the audio quality will also differ if your audio file has a surround sound signature. PCM can only support 2.1 channel audio which means if you have a device with 5.1 channel audio or surround sound capabilities with advanced audio formats then you cannot listen to surround sound. Either way, there is less likely that your experience will differ with these two technologies if you keep the surround sound option out of the bay.
In terms of connectivity, PCM only supports the wired connection. This is obvious because it does not compress audio while transmitting which is why a large amount of information is needed to be transmitted which is why high-frequency bandwidth is necessary. High bandwidth cannot be transmitted wirelessly because it will cause degradation due to various obstacles and also too much power is needed by the transmitter to produce high bandwidth. Wired medium is only therefore possible to transmit such bandwidth signals. You do not get complete support for coaxial and digital optical cables and even on some devices, you cannot use PCM.
Bitstream on the other hand supports both wired as well as wireless mediums. The wireless medium comprises Bluetooth, NFC, WIFI, etc. Bitstream can transmit over any of those mediums and so it supports a variety of frequencies. It supports wired connection as well. So, you get complete support for coaxial and digital optical cables, which means through HDMI you will be able to enjoy spatial audio also.
PCM technology does not compress the audio on the transmission so they decode audio before transmission and transmit the already decoded file. This requires a huge chunk of information to be transmitted. But here the receiver has to do no job in processing and decoding the audio file, it just plays the audio as it is. This lowers the audio lag because of less processing and transfer of raw data. PCM decoders also use a clock frequency which is critical for their operation. The clock pulse from the encoder should match with every clock pulse of the decoder which if not happened can result in faulty transmission.
Bitstream technology compresses audio which is the responsibility of the encoder from the source and this encoded information is then decoded at the receiver’s end. The encoder and decoder do not follow clock format as they only attach redundant bits with every piece of information this redundancy is checked by the decoder to detect and correct errors.
Secondary Audio Quality
Secondary audio refers to the audio which is multichannel audio. It can be a foreign language narration (any foreign language which helps a viewer), sports commentary, or a description of something shown on the screen. You might hear in Marvel’s exclusive Blu-ray CDs where directors and other actors comment on scenes and provide extra information which plays above the actual audio track. This secondary audio track sounds better in PCM technology. If you want to listen to secondary audio tracks then PCM is preferable.
Bitstream technology does not play secondary audio tracks efficiently as PCM. This is because in bitstream a series of bits are transferred so only all information are combined in that track and the receiver only decodes and plays it. In PCM however, different frequencies are transferred at a single time which is where you can enjoy the advantage of multichannel. In short, PCM can process primary and secondary audio simultaneously better than bitstream.
Where Bitstream transmission is modern and preferable because it supports spatial audio and wireless transmission with advanced codecs it falls short on supported devices. PCM transmission works on a maximum number of devices and all older devices as well. It is still the standard transmission technology used. PCM falls short in its ability to only transmit over a wired medium because the more amount of bandwidth makes it impossible to transmit over the wireless medium.
Bitstream’s low bandwidth capability to transfer bits and also supporting so many formats over both wired and wireless medium gives you a greater amount of freedom to build your own home theatre with a variety of speakers which makes your home sound like a theatre.
When should you choose Bitstream?
So, the important points about bitstream to remember are, this technology supports various advanced formats for spatial or surround sound output. It can also transmit over wired and wireless mediums as well. Your receiver will be your decoder so you have more quality options and you can play high-resolution audio via different Bluetooth codecs – Qualcomm aptX, aptX HD, FLAC, etc. When you want to build your own home theatre and your primary priority is experiencing 3D sound though you can compromise with a bit of delay sometimes then you should definitely choose Bitstream technology. But also keep in mind that you have to pick hardware that is compatible with bitstream technology.
When should you choose PCM?
Choosing PCM is quite straightforward. If you do not have hardware that is not compatible with bitstream then you don’t have the option of using PCM technology. In such a situation, you can only use PCM. Now, PCM isn’t bad though. But if you have the option of choosing between the two then I will tell you the important points that you can consider while using PCM.
PCM only offers wired medium transmission. You do not have the option of using advanced audio formats or any advanced codec. Also, there is no support for spatial sound which means if you are building a home theatre then all the speakers will sound the same. You can only have the support of stereo sound.
PCM has an advantage over transmission speed because it has nothing to do with encoding and decoding there will be obviously minimum audio lag noticeable. If you are a gamer and you want your system to be lag-free then PCM might be the option for you. If you have a PCM system but you want to upgrade then I would say the upgrade can be worth it. Because, you will get wireless transmission, better audio quality control, and spatial sound.
Frequently Asked Question
Should TV be set to bitstream or PCM?
If you have a home theatre that supports bitstream, which means it will be able to playback advanced audio formats then selecting bitstream on TV is better. But, if you are using your TV speakers then I would say PCM would be a better option.
Is Dolby Atmos Bitstream or PCM?
Dolby Atmos is Bitstream, in fact, any surround sound option is bitstream. All Dolby, DTS and other advanced formats are Bitstream.
We have mentioned all the differences between Bitstream vs PCM and we hope this article is helpful for you to choose between them. For more such informative content, don’t forget to check out our website: vs – Beat Mentors