Bitstream And Pcm

[scottyg]

Can someone breakdown what the difference between pcm and bitstream is ?
Thanks

 

[avaserfi]

In the context you are asking it seems PCM will be one altered by the source. So if you have a DTS track on a DVD and you have the DVD player set to decode DTS it will output a PCM.

Bitstream is an exact bit for bit copy of the data. So for the same example instead of the DVD player decoding the DTS track it send all the information to your receiver so the receiver can decode it instead.

 

[MDS]

A bitstream is literally a 'stream of bits' - a sequence of one bit after another (serial).

PCM is the lowest common denominator in digital audio. It is a sequence of numbers that represent the amplitude of an analog signal at points in time (example: 44,100 16 bit numbers for every second of audio of each channel on a CD). PCM is a bitstream too.

In the context of receivers and dvd players, the Bitstream setting means 'don't touch it' whereas PCM means 'convert it to PCM'. To follow up on avaserfi's example, if you have Dolby Digital on a disc and these settings in the player:

- Bitstream: The player will just read the bits off the disc and transport them through the digital output to the receiver. The receiver will identify what the bits mean, decode them, and then convert to analog and amplify.

- PCM: The player will decode the bits and convert them to PCM. The receiver will just do the conversion to analog and amplify.

- PCM, but using analog connections to a receiver: The player will decode the bits and convert them to PCM AND do the digital to analog conversion. The receiver gets the analog signal and just amplifies it.

 

[Buckle-meister]

- Bitstream: The player will just read the bits off the disc and transport them through the digital output to the receiver. The receiver will identify what the bits mean, decode them, and then convert to analog and amplify.

- PCM: The player will decode the bits and convert them to PCM. The receiver will just do the conversion to analog and amplify.

So the difference is one of decoding. The receiver must have PCM before it can convert digital data to analogue and amplify it. With Bitstream the receiver does the decoding and with PCM the player does the decoding.

Is this correct (I've seen plenty of these threads and I still get confused)?

 

[MDS]

So the difference is one of decoding. The receiver must have PCM before it can convert digital data to analogue and amplify it. With Bitstream the receiver does the decoding and with PCM the player does the decoding.

Is this correct (I've seen plenty of these threads and I still get confused)?

You are correct sir.

 

[Buckle-meister]

You are correct sir.

Yes!

Presumably, it's at this point that it can make a (small/big?) difference which, between the receiver and player, has the better DAC?

 

[Seth=L]

MDS, it is great how easy is to understand your posts. I really appreciate your linguistic abilities.

 

[scottyg]

I have an yammy rx-v2600 which does not have a setting for dolby hd or dts hd........but it does except hdmi 1.1 for audio support and does have a pcm setting.....can someone tell me what to set my reciever to and dvd player I have a toshiba d2 which supports true hd can my reciver output this ?

 

[MDS]

I have an yammy rx-v2600 which does not have a setting for dolby hd or dts hd........but it does except hdmi 1.1 for audio support and does have a pcm setting

The only setting on a receiver where you would have a choice of Auto, PCM, or DTS is the digital input format. It is probably set to Auto by default and that is what it should be set at.

.....can someone tell me what to set my reciever to and dvd player I have a toshiba d2 which supports true hd can my reciver output this ?

The receiver does not have onboard decoders for TrueHD so you'd need to set the player to output PCM.

 

[emorphien]

Yes!

Presumably, it's at this point that it can make a (small/big?) difference which, between the receiver and player, has the better DAC?

That's how I understand it.

If your DVD player and receiver both can do the digital to analog conversion, you could use the one with the presumably better DAC to perform the task.