is basically the raw "undecoded" data being sent from the TV or Blu-ray Player or Cable/Satellite Receiver or Gaming Console to the Audio Receiver or Sound Bar for it to decode.
(Pulse-Code Modulation) means that the TV or Blu-ray Player or Cable/Satellite Receiver or Gaming Console is performing the audio decoding and sending the decoded signal to the Audio Receiver or Sound Bar.
Let's use a Blu-ray Player
connected with an HDMI connection to a Home Theater Receiver as an example.
If you set the Blu-ray Player to output audio as PCM
, the player will perform the audio decoding of all Dolby and DTS related soundtracks internally
and send the decoded
audio signal in uncompressed form to your Home Theater Receiver. As a result, your Audio Receiver will not have to perform any additional audio decoding before the audio is sent through the amplifier section and the speakers. With this option, the Receiver will display the term "PCM" on its front panel display.
If you select Bitstream
as the HDMI audio output setting of your Blu-ray Player, it will bypass
its own internal Dolby and DTS audio decoders and send the undecoded
signal to your HDMI-connected Home Theater Receiver. With this setting, the Audio Receiver will do all the audio decoding of the incoming signal. In this case, the Receiver will display Dolby, Dolby TrueHD, DTS, DTS-HD Master Audio, etc... on its front panel display depending on which type of Bitstream signal is being decoded.
As pointed out by
below (post 17951), Dolby Atmos
“object-based” surround sound formats require the Blu-ray Player to be in "Bitstream" mode not PCM. For instance, Dolby wraps up the Atmos "objects" (metadata) into a Dolby TrueHD wrapper. When you send that Dolby TrueHD soundtrack out over HDMI to a Dolby Atmos-capable Receiver in Bitstream mode, the Receiver detects that it is actually a Dolby Atmos track and processes the sound accordingly.
In terms of actual audio quality, whether you have your Blu-ray disc player's HDMI audio output set to PCM or Bitstream doesn't matter. If the decoder in one of these devices is significantly better than the other, there might be a difference in sound quality. But these days, the quality of audio decoding in consumer devices is quite good in general, so that difference is likely to be very small and probably indiscernible.
, there is another factor to take into consideration as to which setting that might be best for your to use. This involves access to secondary soundtracks, such as audio commentaries, descriptive audio, the sounds that onscreen buttons make when you click on them, or other supplementary audio tracks. If access to these audio features is important to you, then keeping the Blu-ray player set for the PCM audio output option might be the best option. On the other hand, you can always make the switch from Bitstream to PCM anytime you wish by going into the appropriate menu settings.