Pcm

[shokhead]

What is it and what do i do with it. I see it in my DVD menu. Is it good,bad or ugly.

 

[MDS]

PCM = Pulse Code Modulation. It is the lowest common denominator in digital audio - a 'raw' format if you will.

An analog signal is sampled so many times per second (eg. 44,100 times for CD) and quantized (the amplitude of the signal at each point in time is converted to a number by the A-D converter). So for CD (16 bits) the numbers will range between 0 and +32767 for the positive going part of the waveform and between 0 and -32768 for the negative going part of the waveform. The numbers represent the amplitude of the signal at each sample point.

 

[MDS]

DVD settings for PCM

The DVD player's menu has settings for Dolby Digital and DTS which can be set to either 'bitstream' (sometimes labelled 'raw') and 'PCM'.

When set to 'bitstream' the player will not touch the digital data that is read off the disc. It passes it directly out the digital output (either optical or coax). This is the setting to use if you connect the dvd player to a receiver or pre/pro that can decode DD or DTS. This is also the correct setting for playing PCM sources, such as CD - it will send the PCM over the digital output and the receiver will do the D-A conversion before amplifying it and sending the sound to your speakers.

When set to 'PCM', the DVD player will decode the multi-channel DD or DTS and down-mix it to 2 channel PCM. You would use this setting if you use analog cables to connect the dvd player to the receiver (it will undergo D-A conversion to turn the PCM into analog).

Some players also have an additional setting called something like 'PCM Down Conversion' or 'PCM sampling rate'. My Onkyo let's you choose 48 kHz or 96 kHz. Others just say Yes or No (which implies 48 kHz if set to Yes). If set to 96 kHz, then any PCM signal that uses a 96 kHz (or less) sampling rate will be sent untouched over the digital output. If set to 48 kHz (or Yes), the 96 kHz signal will be down-sampled to 48 kHz. If your receiver has 96 kHz or greater capable dacs, set it to 96 kHz or No downsampling; otherwise set it to 48 kHz or Yes for downsampling.

 

[LaserMark4]

Nice Explanation

Nice explanation, Anonymous....

 

[shokhead]

So If you can choose,dont use PCM?

 

[MDS]

If you connect the dvd player to the receiver using a digital cable, then set both DD and DTS options to 'bitstream'. That is the only way to get true multi-channel sound to the receiver.

If you were to set those settings to PCM, then the receiver will never see more than a 2 channel signal. You can turn it back into 5/6/7.1 using a matrix decoder like PLII(x) or Neo:6 but that is not the same as getting the original DD or DTS signal to the receiver.

 

[Johnny Canuck]

What if you have a DVD player connected with both Optical and analog cables? Is there any differnce if you connect an RCA from the analog out on the DVD player or is using the DVD A multi channel RCA's I am using the same thing now?

 

[MDS]

You can connect both the optical and analog cables at the same time if you want. Whether it will use the digital or analog connection is dependent on the dvd player settings (bitstream vs pcm, described above) and the receivers setting. If the receiver is set to 'auto' it will automatically choose the digital or analog signal so it won't need to be changed manually.

 

[Johnny Canuck]

Thanks MDS. A little confusion here. I should have worded my question differently.

The back of my DVD player has 2cannel out as well as 6 channel out for analogue. I do not have the 2 channel set up now. I notice when listening to a CD, and I push "analog" on my Denon remote, I don't get any sound. I wanted to know, if I want to listen to a CD in analog, do I need to have these RCA's hooked up or is there a setting in the DVD player settings that allow me to do this with the multi channel RCA's. Am I making myself clear? sorry if i'm not.

 

[MDS]

How is the player hooked up to the receiver? Just so I understand.

- digital assigned to CD or DVD input, digital cable connected from player to receiver and player set to 'bitstream'. [Would give you digital sound from the player when receiver is set to digital or auto and you select the CD/DVD input]. If you switch to analog with this setup, there will be no sound unless you also connect the 2 analog cables to the CD/DVD input.

- 5.1 analog outs from player connected to ext in. You would have to select the ext in on the Denon. You should be able to hear stereo from a CD with this connection, but the player would have to convert the 2 channel PCM to analog and that it usually accomplished by setting the player to 'pcm'. Your player may have additional options.