Author Topic: Rec 709 color space issues for HDTV viewing. When to use? How to use?  (Read 10493 times)

mannfilm

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Is it correct that all video to be played on a HDTV should be encoded into the Rec 709 or Rec 709 (16-235) color space, otherwise the blacks and whites get clipped, and the colors weird?  And for general public we should use Rec 709 (16-235) because of all the 8 bit consumer HDTV's out there???

So when do we start working in Rec 709 or Rec 709 (16-235)?

I've seen some advocate going RAW to Prores 444XQ and later down-convert to Rec 709???  Yet others (broadcast?) seem to start in REC 709 and stay there. Which is better?

In grading, is there trick or something for encoding into Rec 709 or Rec 709 (16-235)?

Thanks in advance




dyfid

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Re: Rec 709 color space issues for HDTV viewing. When to use? How to use?
« Reply #1 on: August 15, 2014, 12:17:21 AM »
Is it correct that all video to be played on a HDTV should be encoded into the Rec 709

Not any video but any HD Video starting at 720p resolution. If you were viewing DVD, PAL or NTSC then those are different specifications, resolutions, primaries, transfer and colour matrix. It's not the TV display that's decompressing the video and generating the signal.

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or Rec 709 (16-235) color space, otherwise the blacks and whites get clipped, and the colors weird?

It's not so important whether you encode with under and overshoot in digital video realm, what is important is where you reference black and white are at YUV 16 - 235.

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And for general public we should use Rec 709 (16-235) because of all the 8 bit consumer HDTV's out there???

HDTV's are generally expecting to receive a levels range 16 - 235 YUV or RGB Low or RGB Normal. What's important is that the viewer takes care to ensure their TV and media player settings match levels wise. If the wrong levels range is fed to a TV then there will be problems with contrast and gamma.

Checking levels ranges can be done by feeding the TV a few simple images. Not calibration that would be the next step, a LUT box the step after that unless using a PC dedicated for colour managed media playback.

Support for display refresh rates suitable for correct video cadence is also important, a computer monitor capable of only 60Hz refresh rate and sRGB colour space is crippled to handle 23.976 fps Rec709 for example.

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So when do we start working in Rec 709 or Rec 709 (16-235)?

The important bit is monitoring and preview on a calibrated display to specifications that display supports. Whether that be Rec709 HD, PAL or NTSC, LUT'd to be able to swap between the specifications or a media player capable of doing the transforms which is generally what happens, to varying quality.

If only doing Web or TV then Rec709 is the specification to monitor with. Gamma is debatable but BT1886 is suggested for LCD/LED/Plasma as it exists to more closely relate to the old CRT gamma response which many of these video specifications are targeted at.

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I've seen some advocate going RAW to Prores 444XQ and later down-convert to Rec 709???  Yet others (broadcast?) seem to start in REC 709 and stay there. Which is better?

What ever you do in the grading process, you're monitoring it generally Rec709 even for cinema unless you grade using a projector that can do P3. Where you go from raw, what codec you put it in is anyones choice.

btw sRGB monitoring is generally not advised.

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In grading, is there trick or something for encoding into Rec 709 or Rec 709 (16-235)?

Thanks in advance

What you see on your calibrated reference display is or should be what is encoded, what is important is that the correct specification is chosen for encoding.

For example just because a video is encoded to h264 doesn't mean it's Rec709 primaries, transfer and colour matrix. What determines the specification is generally lines of resolution.

Also there appears to be issue with QT h264 encoding on mac's through Resolve and probably any QT based mac app with regard to sticking to the specification and not introducing tweaks to suit its own OS level colour management, resulting in playback on non QT players appearing incorrectly.

mannfilm

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Re: Rec 709 color space issues for HDTV viewing. When to use? How to use?
« Reply #2 on: August 15, 2014, 07:26:48 PM »
Wow! Thank you so much!