Bitstream or Linear PCM setting for PS3?

[jmy350z]

Have a quick question about the PS3 and Onkyo 605. When watching bluray movies,how should I have the Ps3 set, linear pcm or bitstream?

 

[markw]

Dunno about games, but in DVD players PCM passes a two-channel stereo signal while bitstream passes multi-channel sound.

 

[ParadigmDawg]

Yep, bitstream

 

[AcuDefTechGuy]

It depends on which audio format you are using.
PCM will send Uncompressed Audio via HDMI.
Bitstream will send the encoded DTS, DTS-MA, Dolby Digital, D-Digital Plus, D-TruHD to the Onkyo 605 for decoding.

 

[j_garcia]

PCM and LPCM aren't the same thing. LPCM is lossless and multichannel, vs standard PCM that is stereo (or dts 5.1). I would first try LPCM and see how it goes, as most BD movies have a lossless track. Your receiver should be able to decode the bitstream signal too though.

 

[ParadigmDawg]

I stand corrected...

 

[j_garcia]

What it comes down to is the receiver, not many do the decoding yet, so the player needs to either pass the lossless track or convert THD/DTS-HD to LPCM. So I would recommend LPCM for anything below 1.2A HDMI, however the 605 is HDMI 1.3 and probably has the decoders; I haven't checked.

 

[MDS]

Actually PCM and LPCM are the same thing. The L stands for Linear and simply means the samples are stored in linear order 1, 2, 3....

Now if the PS3 uses two different labels, PCM and LPCM, to distinguish between 2 channel and multi-channel that is a different story.

 

[j_garcia]

No, there is no mention of PCM at all, just LPCM, but LPCM in the case of a BD player signified to me that you would be doing the conversion in the source itself and was differentiating the fact that you could play lossless (and new formats, TrueHD/dts-HD) audio this way, something the unit won't do via the optical connection (you get stereo only ala PCM). My understanding is they are the same, but two different flavors of that same thing - maybe I am misunderstanding that. I know regular PCM can be fooled to pass a 5.1 signal, aka dts-CDs, but that isn't quite the same as multichannel lossless audio being passed via LPCM, even if it is done the same way.

 

[AlphaWolf]

Actually PCM and LPCM are the same thing. The L stands for Linear and simply means the samples are stored in linear order 1, 2, 3....

Now if the PS3 uses two different labels, PCM and LPCM, to distinguish between 2 channel and multi-channel that is a different story.

I don't want to pretend I am an expert at any of this, but from what I understand, PCM just refers to how a single audio channel is modulated, and in any given system you can only "modulate" one channel at a time. In the case of audio you have e.g. amplitude (proportion) Y at sample number X in your "channel."

LPCM defines how to combine more than one PCM channel into a single linear bitstream instead of multiple separate bitstreams. So technically only mono audio should be referred to as straight PCM.

Remember though PCM isn't just used for audio. Pretty much anything digital is going to use either PCM or QAM modulation. A dialup modem is a good example of PCM modulation, and a cable modem is a good example of QAM modulation.

 

[AcuDefTechGuy]

I think when people say "PCM", they actually mean "Linear PCM" and vice versa.
Bottom line is, there is a 2-Channel LPCM, 5.1-Channel LPCM, and 7.1-Channel LPCM.
The Sony PS3 is capable of 7.1-Channel LPCM via the HDMI 1.3.

However, since the Onkyo AVR-605 has decoders for Dolby TruHD, Dolby Digital Plus, DTS-HD, and DTS-HD MA, you would want to use Bitstream to get these sound formats; otherwise, you will have to set the PS3 to LPCM for Uncompressed audio when available.

 

[j_garcia]

No, if you look up PCM, the "standard" version is not linear. And if you look up LPCM you will see that it is a form of PCM:

LPCM is a particular method of pulse code modulation which represents an audio waveform as a sequence of amplitude values recorded at a sequence of times. LPCM specifies that the values stored are proportional to the amplitudes, rather than representing say the logarithm of the amplitude, or being related in some other manner. In practise these values will be quantized.

 

[MDS]

I don't want to pretend I am an expert at any of this, but from what I understand, PCM just refers to how a single audio channel is modulated, and in any given system you can only "modulate" one channel at a time. In the case of audio you have e.g. amplitude (proportion) Y at sample number X in your "channel."

LPCM defines how to combine more than one PCM channel into a single linear bitstream instead of multiple separate bitstreams. So technically only mono audio should be referred to as straight PCM.

Negative.

In this case we are talking about PCM as a data encoding format - not how digital data, in any format is transmitted (modulated) over a wire.

PCM and LPCM are used interchangeably although the format can actually vary somewhat. Briefly, an analog signal is sampled at points in time and an amplitude value is calculated for each sample. Rather than store that number directly, each value is instead assigned a code - think of it as a lookup table that maps values in the range of the bit depth to a unique code value.

A CD is encoded in PCM. The sample values are linear - left channel sample 1, right channel sample 1, left channel sample 2, right channel sample 2, ....
If it were multi-channel it would be similar except using samples 1-N. Same exact thing for a WAV file except that the sample values are preceded by a header with bookkeeping information such as how many channels, sample rate, bit depth, length of the file, etc.

Now the format can vary slightly if we are talking about storing it as a digital audio file. The sample can be signed or unsigned, they can be stored most significant bit first or least significant bit first