[opendtv] Re: TV Technology: A New Day Dawning... HDR Delivery
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 8 Jun 2016 02:27:42 +0000
Jeroen Stessen wrote:
Our HDR encoder is a variable compressor, it outputs an SDR
grade. Our HDR decoder is an expander, controlled by a little
bit of dynamic metadata so that we can adapt the tone mapping to
the content (for preserving the story).
Hi Jeroen and Donald. Glad to hear from you again.
Your description is what in audio is called, I think, "companding." It's used
in digital telephony, for example, and in the latter days of vinyl records and
analog audio tapes, hadn't Dolby developed such a technique for audio? Yes, it
was called dbx. They did this to reduce the amount of apparent noise in the
recording.
https://en.wikipedia.org/wiki/Dbx_(noise_reduction)
The other thing I wanted to mention is that the public is being misinformed
about HDR, at times. I read an explanation of "HDR mode" used in some
smartphones, for taking pictures. It wasn't HDR at all. If anything, it was
dynamic range reduction.
The explanation was that in HDR mode, the smartphone takes three pictures
instead of one. Each picture is exposed differently. Then, the phone creates a
single picture out of three. It removes any part of the picture that is
overexposed or underexposed, replacing those with snippets that are better
exposed.
Naturally, the results are demonstrated on SDR displays, and naturally, they
look way better than the original typically-exposed picture. The overly dark
parts are clearly visible, as are the washed out parts. But this is not HDR.
It's RDR (reduced dynamic range).
Anyway, by your explanation, I would expect the SDR rendition to be quite good.
It would be a dynamically compressed image, with nothing too dark and nothing
too washed out. A "proper" HDR image could be re-created without need for
simulcasting. Sounds good to me!
Bert
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