Actually, I could pull quotes from many sites that show the same or similar definition.
Well, yes, but again, the definition itself doesn't say anything about definition #4 being inappropriate. That is happens to be the least common usage is immaterial if it's still correct. You haven't provided for us an authoritative source to that effect.
Transcode, in the narrower sense of the word means to convert between two different types of encoded data. It doesn't mean filter *or* combine.
I agree with the first sentence, but the second is a bit ill-posed. First of all, filtering can indeed be a part of the transcoding process; indeed, it might even be necessary in certain instances. For example, the term is often used to describe the process of conversion between DSD and PCM; and in such case, filtering is a fundamental part of the process. Furthermore, I'm frankly not even sure what you mean by "combining" in this context. Are you simply referring to the combining of multiple independent signals (e.g. component video) into one (e.g., S-Video)? If so, I think this represents an unnecessary limited view of signal processing. After all, the three component signals are in fact part of a single cohesive whole, and people deal with multiple simultaneous signals in the mathematical side of things without much difficulty.
In the digital domain, Transcode implies a much more sophisticated process between two more different types of information Taking an NTSC signal and converting it to HDTV would be a better use of the word transcode.
Hmm, no, I'd say that's an "upconvert".
Converting a PC program to MacIntosh via an algorithm would be a better use of the word transcode.
I'd have to disagree. At the source code level, this is not transcoding, because in fact the format stays the same, it's the content
that has to change. At the binary level, people talk about emulation or translation, but I've never
heard of transcoding in this context. It's not my field of expertise by any means; they're the next building over
If you can find even a single Google page from a competent source that uses the term in this way, I'd be genuinely interested to read it.
Typically, a transcode changes data from one type of another encode and, as I understand it, without having to decode the data.
Well, then you'd better be careful to define "decode". Because in fact, I don't think you'll find an audio transcoder (MP3->AAC, AAC->Ogg, FLAC->MP3, whatever) that doesn't involve decoding the source format before re-encoding to the destination format.
It generally implies the use of an algorithm, not a filter set.
You say this as if these are so easily distinguished... again, transcoding can often involve filtering.
But, the genesis of the "up" is to denote whether the signal is being filtered or combined. If you are filtering, that is "upconversion". If you are combining, that is "downconversion".
I do see the merit in this distinction, as it is similar to the way upconversion and downconversion is used in digital signal processing (though a bit different from its original usage in radio). So I'll back off my total rejection of "upconvert" to describe the conversion of, say, composite to component. However, I think that "transcode" is also justifiable in these contexts because the information content is preserved.