Blu-ray Player / Bitstream vs. PCM
Blu-ray Disc players have a number of audio and video output adjusting options, depending on how you have your Blu-ray player appropriately connected to your “Home Theater” receiver.
When you have your Blu-ray Disc player connected to your “Home Theater” receiver via HDMI, there are two main audio output settings available: Bitstream and PCM. In situations of actual audio quality, It doesn’t matter if you have your Blu-ray disc player’s HDMI audio output set to PCM or Bitstream. Then again, here is what happens when you select either setting:
When you set your Blu-ray Disc player, set your player to output audio as PCM, the player will perform the audio decoding of all Dolby Digital TrueHD and DTS/DTS-HD Master Audio, they are related soundtracks internally and will send the decoded audio signal in uncompressed form to your “Home Theater” receiver. As a result, your “Home Theater” receiver will not have to perform any additional audio decoding before the audio is sent through the amplifier section and the multi-speakers. With this preference, the “Home Theater” receiver will display the term “PCM” on its front panel display.
When you select Bitstream as the HDMI audio output setting of your Blu-ray player, the player will bypass its own internal Dolby and DTS audio decoders and send the un-decoded signal to your HDMI-connected “Home Theater” receiver. With this setting, the “Home Theater” receiver will do all the audio decoding of the incoming signal. As an effect, in this case, the receiver will display Dolby, Dolby TrueHD, DTS, DTS-HD Master Audio on its front panel display depending on which type of Bitstream signal is being decoded.
Options are as to which setting to use, and as mentioned above, either setting should produce the same audio quality. However, there is another factor to take into consideration as to which setting that might be best for you to use. This comprises access to secondary soundtracks, such as audio commentaries, descriptive audio, or other supplementary audio tracks. If this access to these audio features is significant to you, then keeping the Blu-ray player set for the PCM audio output option might be best the best option for you. On the other hand, you can always make the switch from Bitstream to PCM anytime you wish by going into the Blu-ray remote menu settings.
Blu-ray Disc Secondary Audio Setting:
There may be an additional adjusting option that may be available on your Blu-ray Disc player that is “BD-Secondary Audio”. Using this setting combines both the main high-resolution audio (Dolby TrueHD or DTS-HD Master Audio) signal with the secondary audio signal. However, if using this setting, the Blu-ray disc player will “let-down” the Dolby TrueHD or DTS-HD to standard Dolby Digital or DTS in order to be able to squeeze both types of audio signals into the same bandwidth via Bitstream. In this case your “Home Theater” receiver will recognise the signal as standard Dolby Digital and decode applicably.
Digital Optical / Coaxial vs. HDMI Connections:
Also, if you are using either the Digital Optical or Digital Coaxial connection option from your Blu-ray disc player to your “Home Theater” receiver, this is handy if your “Home Theater” receiver does not have HDMI connections, you can also select PCM or Bitstream output options as well for those connections. On the other hand, while the Bitstream output option can send a Dolby Digital or DTS 5.1 surround sound signal to your “Home Theater” receiver for further decoding, the PCM option will only send a two-channel signal. The reason for this is that a digital optical or digital coaxial cable does not have the acceptable bandwidth capacity to move a decoded, uncompressed, full surround sound audio signal just like an HDMI connection can do.