Re: What does PCM mean to you?

Jon Harris wrote:
"Jerry Avins" <jya@xxxxxxxx> wrote in message news:sMydnckE6OIQFN_eRVn-jg@xxxxxxxxxx

Matt Timmermans wrote:

These days, PCM is the name given to the common uncompressed representations of audio signals as bit sequences. Yes, I know
that's silly, but that's the way it is.

If there's general agreement on the issue (there hardly seems to be), that's fine with me, but nobody told me about it. Can you cite
any credible sources? (Credible is a step down from authoritative.) There was a time when many took "communist" to mean
any individual who disagreed with the speaker's politics, but that
didn't make it so.

I'm in agreement with Matt regarding the common use of PCM, at least
in the consumer audio industry. The term "PCM" in exactly the sense Matt describes is used many times my home DVD player's documentation (JVC XV-SA600). Some examples:

I don't think the examples are using it in the "common use" sense you mean. Let's look at them one by one:

"There are some audio formats recorded on discs as shown below.
Linear PCM Uncompressed digital audio, the same format used on CDs
and most studio masters."

Here it's qualified as "Linear ... Uncompressed", to give it the "common use" sense you expect.

"DVD with 192/176.4/96/88.2 kHz, 16/22/24 bit linear PCM" 

Here again "16/22/24 bit linear ...".

In fact, the digital output is labeled "PCM/Stream" (stream is used
to  refer to Dolby Digital and other compressed/encoded formats).

I.e., the general term "Pulse Code Modulation", or "Stream" (of bits) is used to cover any encoded sequence of bits, not just linear.

PCM originally referred to the transmission of data samples as a stream of pulses chosen from a code set, as opposed to PWM (Pulse Width Modulation), where the width of each pulse would be proportional to the amplitude of the data sample, or PAM (Pulse Amplitude Modulation), where each pulse would be proportional to the amplitude of the data sample. The code set wouldn't need to be "zeros and ones", but could be something more complex, like "one, zero", "one, one", and so on (where each "zero" or "one" actually represents a pulse shape). It's all pretty logical.

Paulo
.

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