On 2020-10-03 08:44, Mark Filipak (ffmpeg) wrote:
…I INTERRUPT THIS PROGRAM FOR AN IMPORTANT ANNOUNCEMENT.
The text two paragraphs below was my original response. I include it
just for the sake of completeness and for Jim's benefit, however,
things have... progressed (in a way).
My goal (for a long time) is to differentiate hard telecine from
pseudo NTSC (which I'm calling d-NTSC). I thought I'd found the
differentiation: The combined values of 'progressive_sequence' and
'progressive_frame' MPEG-PS metadata. I was wrong. The video that I
thought was hard telecined was actually soft telecined. When I
realized my error, I revised my response:
"'progressive_sequence' = 0 & 'progressive_frame' = 1 means that the
frame is soft telecined",
and only then realized that I'd screwed the pooch: that I still had no
way to differentiate hard telecine from d-NTSC. I'm withdrawing the
d-NTSC & d-PAL entries and will rework them when I can, in fact,
differentiate d-NTSC & d-PAL from hard telecine. (sigh!)
WE NOW RESUME OUR REGULARLY SCHEDULED PROGRAM.
If I understand your point, it is that the definition is followed by a
table (of sorts) that you think is content and not a suitable part of
the definition. Okay, let me try to explain and maybe you can suggest
a better way, eh?
The 'table' isn't really a table. It's the metadata values that are
necessary for the d-NTSC frame to be a d-NTSC frame. I provide it so
that readers can verify that, "Yes, indeed, I'm looking at a d-NTSC
frame". The big clue is that 'progressive_sequence' (from the
sequence_extension metadata structure) and 'progressive_frame' (from
the picture_coding_extension metadata structure) are both zero. My
friend, it took me months to figure that out because H.262 doesn't put
things together. Here's the straight dope:
'progressive_sequence' = 1 means the frame is a picture.
'progressive_sequence' = 0 & 'progressive_frame' = 0 means that the
frame is d-NTSC or d-PAL.
'progressive_sequence' = 0 & 'progressive_frame' = 1 means that the
frame is soft telecined.
Without that info, you can't tell d-NTSC from hard telecined unless
you single step through the video frames and know what to look for.
The other metadata in the 'table' is the rest of the stuff that
distinguishes d-NTSC from d-PAL: width, height, aspect ratio, etc.
So, you see, the metadata has to be part of the definition, or at
least that's what I think.
Do you have a better idea?
When you say, "My goal (for a long time) is to differentiate hard
telecine from pseudo NTSC (which I'm calling d-NTSC).… [using] MPEG-PS
metadata", it sounds to that your goal is to describe different content
structures in the context of an MPEG-PS stream. The right document for
doing this work is a guide to or explanation of MPEG-PS stream contents.
As part of describing a content structure, it is probably quite helpful
to list the metadata values which identify that structure. But this
document is not a glossary.
It also sounds to me like you are coining the term "d-NTSC" to name one
kind of content structure. It is perfectly in scope to define names in
such a guide or explanation. But it sounds like you aren't claiming
that the term "d-NTSC" is [also] defined by some other document, such as
the H.262 specification. Fine.
In the glossary, I would expect to see a term, e.g. "d-NTSC", and then
one or more entries describing meanings of that term, each with an
explanation of the term and a cross-reference to where the term is
defined or used in an important way, e.g. to "Mark's Guide to MPEG-PS
Stream Content Structures", section X.Y, "pseudo-NTSC content".
Or simply put, what you are drafting in this thread is an entry in
Mark's Guide to MPEG-PS, not a glossary entry. In my humble opinion.
—Jim DeLaHunt
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