Timeline for What specifically does PCM refer to?
Current License: CC BY-SA 4.0
6 events
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| Oct 24, 2020 at 8:40 | comment | added | Lewis Kelsey | Well, line coding in general is actually the mapping of an already serialised bitstream to amplitudes. Like MBaz says, PCM traditionally encompasses that outcome of the samples | |
| Oct 24, 2020 at 8:28 | comment | added | Lewis Kelsey | ... is a function that serialises discrete samples and maps to amplitudes. | |
| Oct 24, 2020 at 8:28 | comment | added | Lewis Kelsey | it's a bit like how you could call modulating an OFDM symbol with a carrier 'AM', because this appears as a continuous level continuous-time analogue waveform multiplied by a carrier in the analogue domain—I don't think I would, same with how if this were sampled it wouldn't be PCM, because it's still ultimately a digital signal. I think you're right: PCM is a function that multiplies a signal with a Dirac comb and maps amplitudes to samples. Analogue PAM is a function that multiplies with a Dirac comb and line coding (which includes digital PAM)... | |
| Oct 23, 2020 at 21:22 | comment | added | Nigel Redmon | Good question. I'd say that PCM is the starting point. You can see that in the name "adaptive differential PCM", for instance. The sample values no longer directly represent sampled levels. Same with mp3, AAC. They all started with PCM, though. Theoretically, you could obtain the analog sample (fundamentally PAM), do analog processing (differential, etc.), they digitize it and never truly be PCM, but starting with PCM and applying such techniques is more practical. Offhand, I can't think of any case where the data weren't at least derived from PCM, for audio at least, maybe someone else can. | |
| Oct 23, 2020 at 7:51 | comment | added | Lewis Kelsey | So PCM is just the sampling and quantising part? That's a bit weird doesn't that theoretically make all signals in the digital domain PCM, as they're just discrete sets of samples. I think the emphasis is on that it's an analogue rather than digital waveform being sampled | |
| Oct 22, 2020 at 16:42 | history | answered | Nigel Redmon | CC BY-SA 4.0 |