PCM and Bitstream: Which is more common?

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henryscott136

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Hi everyone. I have been doing some research for a dissertation I've been writing, trying to find out whether surround sound will ever take over and become more common compared to stereo systems for gaming. I've been looking into audio formats used for surround sound and by far, it seems that PCM is a much better format than any bitstream format such as Dolby and DTS. But when looking at different AV amplifiers and receivers, many support Dolby TrueHD and DTS HD and not PCM. Does anyone know why this is and if so, could you possibly link me to an article that might explain this? I am new to all of this so sorry if I sound too ignorant, but I could really use some help. Thanks.
 
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Whoa.....

Alright. First, there is no uncompressed/compressed PCM, PCM is an algorithm for representing an analog wave digitally and has been around since the beginning of the 1900's. This is not the only algorithm out there, there's pulse width modulation, pulse position, pulse density, delta-sigma (which is used with DSD), and others but PCM is by far the standard (for audio). PCM itself comes in a couple of flavors, regular PCM where quantization levels is a function of amplitude, and LPCM where quantization levels are uniformly linear (hence linear pulse code modulation).

Since PCM is an algorithm, compressed/noncompressed doesn't make any sense from a technical standpoint, it takes an input and gives you an output and doesn't...
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Rocky Bennett

Rocky Bennett

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Both Dolby and DTS are companies that have developed their specific CODECs as a means of compressing audio streams. PCM is uncompressed and as such should theoretically offer a better audio stream, but since Dolby TrueHD and DTS HDMasterAudio are uncompressed CODECs, the audio stream is identical to the source.

I prefer PCM or even LPCM, but I guess that because hardware manufacturers have to pay money for licensing, they really favor DTS and Dolby.
 
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americanaudiophile

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Lossless audio codecs (DD or DTS) were all that fit onto DVDs and in the case of Dolby Digital OVA and cable TV (less bandwidth required). Also pre HDMI there wasn't a standard cable that could carry the larger data load of lossless codecs so these were developed along with HDMI for Blueray.
BD players can be set to output in multichannel PCM so that the surround processing is done in the player or to let the surround system do the processing which is usually better given the cost difference.
 
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Rocky Bennett

Rocky Bennett

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This is not true at all. DVDs only held lossey CODECs, not lossless as you indicated. Also, PCM and LPCM was very common with the old DVDs.
 
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Ruggo181

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It's really a question that you should be asking the source creators. They are the ones that decide which audio is being used.

As to one being better than the other, well if a audio stream is properly decoded, I'd like to see a person in blind tests hear the difference.
 
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Rocky Bennett

Rocky Bennett

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At Ruggo181, if you are specifically referring to Dolby True HD and DTS HD Master Audio and uncompressed PCM, then I do agree with you. If you are talking about Dolby Digital, regular DTS and PCM, then there is a world of difference and anyone can tell the difference.
 
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Ruggo181

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I stopped reading after uncompressed PCM.............

 
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Rocky Bennett

Rocky Bennett

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HA! HA! HA! Cheers to you when you know when you're over your head. Yes, it gets a little complicated when you start comparing compressed CODECs with uncompressed CODECs with just pure uncompressed PCM audio streams. Audio is a complicated hobby and since I got into the digital aspect of it back in the 1970s things have certainly evolved.
 
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Ruggo181

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Sort of, except there's no such thing as compressed PCM ......
Anyhoo, I think you and I have different takes on Digitalised Audio, so we could to and fro forever and derail this thread, or agree to disagree ;)
 
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Rocky Bennett

Rocky Bennett

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Hello Ruggo181, You are probably right about our philosophical differences regarding digital sound formats, but you are absolutely incorrect about "no such thing as compressed PCM." Uncompressed PCM audio is commonly referred to as LPCM (linear pulse code modulation) but there are many ways to compress PCM audio signals. The most common compressed PCM CODEC is something called MP3. I am sure that you have heard of MP3s, they are a CODEC that contains a compressed PCM signal. http://faq.yamaha.com/us/en/article/music-production/recorders/pocketrak_cx/4918/2840/what_is_the_difference_between_linear_pcm_and_mp3_recording

Other than that, there are many ways to compress PCM signals and maintain the basic PCM aspect of the signal, but I thought that I would just mention MP3 because it is the most common method of compressing PCM while still being PCM.
 
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ien2222

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Whoa.....

Alright. First, there is no uncompressed/compressed PCM, PCM is an algorithm for representing an analog wave digitally and has been around since the beginning of the 1900's. This is not the only algorithm out there, there's pulse width modulation, pulse position, pulse density, delta-sigma (which is used with DSD), and others but PCM is by far the standard (for audio). PCM itself comes in a couple of flavors, regular PCM where quantization levels is a function of amplitude, and LPCM where quantization levels are uniformly linear (hence linear pulse code modulation).

Since PCM is an algorithm, compressed/noncompressed doesn't make any sense from a technical standpoint, it takes an input and gives you an output and doesn't care what the data is.

Because this is the standard (for audio), pretty much everything uses it AVR, pre/pro, stereo receiver, sound cards/on board sound, pretty much everything that deals with converting digital to audio (and audio to digital) uses PCM at the bottom of the chain.

But like a lot of things it takes on new meanings though it's not necessarily correct in the strictest sense, in this instance many people also include the digital output as just "PCM" also. Well, it's just a data file you can call it PCM data file but when it's just referred to as PCM misunderstandings happen (and the thing you have to understand is that going from analog to digital isn't 1 to 1, going from digital to analog is though so in a broad general sense PCM is a lossy compression algorithm itself). That data file isn't very useful unless you know the parameters used by the PCM encoding so we use headers and containers for streaming/storage.

Wav, aiff, flac, ogg, mp3, DD, DTS, etc are all containers, some happen to be more than just that such as flac, mpeg, DD, DTS (and others) which are also a compression algorithm(some lossy, some lossless) and/or encoding scheme. When you play any of these formats, they all are converted to PCM data for the DAC to use. Yes, I know, you see chips that include DD/DTS decoding and they do that, but it's still a conversion to PCM data first before converted to analog.

So back to the original post:

First correction, all AVR's and digital stereo/receiver will play a PCM stream as far as I know, perhaps multichannel PCM isn't available for all though. I don't think it's really ever listed in marketing...or even some manuals at this time.

So, PCM vs DD/DTS. As you can see above, that question doesn't really make any sense. Since we are talking about a data file, we don't have to use a analog to digital converter to create a data file (think synthesizers and such), so you can create an extremely good quality DD datafile and a poor quality PCM data file on the computer where the DD will be far better than the PCM data. Now I know most people look at that question and assume that the DD/DTS data is created from the PCM data in which case the answer would be yes, PCM data would be better than lossy DD/DTS and would be equal to the HD encoding, but your question is in reference to gaming and alot of the stuff out there is computer generated.
 
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Rocky Bennett

Rocky Bennett

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Wow, that certainly was a mouthful. I appreciate your input into this thread except that I disagree with just a couple of points. First, not all stereo receivers play a PCM stream. In fact, none of the receivers that I own can play a PCM stream, they can only play an analogue stream. Of course I own outboard DACs to compensate for this, but I prefer my system set up like that.

Also, DSD is my favorite digital audio format. I own many DSD files and discs and love the sound of DSD.

But I loved your post. Thanks.
 
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ien2222

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I did specially say digital stereos/receivers in reference (though I probably should have specified) to having an SPDIF input or networking for that matter. Since you can have DSP in various kit with only analog inputs and I guess you can call it digital, I should have been a bit clearer on what I meant. :D
 
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ien2222

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I should point out it's a bit more complicated than what I posted but it's probably good enough for the question at hand.

Just for a fun fact, the first patent for a fax machine using PCM for transmission was issued in 1926, twenty years before ENIAC was completed.
 
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