FreeSat SD and HD - limited or full-range RGB? - AVS Forum
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post #1 of 7 Old 02-10-2013, 01:12 PM - Thread Starter
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Hi,

I have a Grundig FreeSat receiver connected to a Samsung HDTV, and I'm trying to determine whether to use the Low or Normal Black Level. There's no apparent user-facing way to adjust the black level on the Grundig, so I guess the question is simply: do FreeSat SD and HD broadcasts here in the UK use full-range RGB or the limited (16-235) range? Or does it depend on the channel?

Please refrain from simply asking me which looks better, because with calibration they each have benefits and drawbacks.

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post #2 of 7 Old 02-10-2013, 01:40 PM
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Originally Posted by docker2 View Post

Hi,

I have a Grundig FreeSat receiver connected to a Samsung HDTV, and I'm trying to determine whether to use the Low or Normal Black Level. There's no apparent user-facing way to adjust the black level on the Grundig, so I guess the question is simply: do FreeSat SD and HD broadcasts here in the UK use full-range RGB or the limited (16-235) range? Or does it depend on the channel?

Please refrain from simply asking me which looks better, because with calibration they each have benefits and drawbacks.

Ta smile.gif

PM Sneals2000. It is 16-235 in the USA and I believe the same in the UK. But Sneals will know for sure.

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post #3 of 7 Old 02-10-2013, 04:46 PM
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Originally Posted by docker2 View Post

Hi,

I have a Grundig FreeSat receiver connected to a Samsung HDTV, and I'm trying to determine whether to use the Low or Normal Black Level. There's no apparent user-facing way to adjust the black level on the Grundig, so I guess the question is simply: do FreeSat SD and HD broadcasts here in the UK use full-range RGB or the limited (16-235) range? Or does it depend on the channel?

Please refrain from simply asking me which looks better, because with calibration they each have benefits and drawbacks.

Ta smile.gif

All digital broadcast TV - ATSC, DVB, ISDB - we receive at home uses 16-235 colour space. It's also the broadcast standard used around TV studios in both SDI and HD-SDI environments (or the 10 bit version is), and is also used by DVD and Blu-ray. (It's defined in ITU 601 and 709 for SD and HD respectively)

Freesat, Freeview, Sky etc. will all output 16-235 levelspace via HDMI.

(Also - chances are that your box will output YCrCb not RGB - that is what is broadcast)
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post #4 of 7 Old 02-10-2013, 05:01 PM - Thread Starter
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That answers a lot of questions for me, thanks Sneals2000.

So, if I'm watching an iTunes-purchased HD movie, or a DVD, from my Mac sent over HDMI to my HDTV, I should have the HDTV calibrated to a Low Black Level, not Normal?
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post #5 of 7 Old 02-11-2013, 02:57 PM
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Originally Posted by docker2 View Post

That answers a lot of questions for me, thanks Sneals2000.

So, if I'm watching an iTunes-purchased HD movie, or a DVD, from my Mac sent over HDMI to my HDTV, I should have the HDTV calibrated to a Low Black Level, not Normal?

Not sure - will depend on the Mac drivers. Some drivers get HDMI 'right' (i.e. send 16-235) whilst others treat it more like DVI (and send 0-255). I don't have a Mac with an HDMI output so can't confirm what it does.

It's likely that the source video within the H264 iTunes video is going to be 16-235, but then what the Mac does with this I don't know. (It could be expanding to 0-255, and then compressing back to 16-235)
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post #6 of 7 Old 02-13-2013, 11:49 AM - Thread Starter
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Darn, that prompts even more questions:

1) How can I determine whether or not my HDMI data is being output correctly?

2) I calibrated my HDTV's greyscale using 10-step IRE patterns from my MacBook Pro running Windows 7, outputting over ThunderBolt to HDMI adapter. If the HDMI data isn't being sent as limited range, will this have messed with my calibration?
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post #7 of 7 Old 02-14-2013, 06:48 AM
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Originally Posted by docker2 View Post

Darn, that prompts even more questions:

1) How can I determine whether or not my HDMI data is being output correctly?

I usually end up trusting my eyes with known good sources. I route all but my Sky box through an AV amp to the same HDMI input - so calibrate the display against a known-good HDMI source (usually my standalone Blu-ray player), and then make sure my HTPC matches it and isn't horribly crushed or sat-up.
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2) I calibrated my HDTV's greyscale using 10-step IRE patterns from my MacBook Pro running Windows 7, outputting over ThunderBolt to HDMI adapter. If the HDMI data isn't being sent as limited range, will this have messed with my calibration?

Possibly... Beware as well that different video players will do different things with 16-235 sources. Some try to 'help' by doing stuff outside the domain of the drivers.

I use a Video Essentials Blu-ray for line-up usually - as well as a recording of the BBC HD Test Signal. I chose my player app, look at the configs in that for level space, and also look at the driver configs. There have been longstanding issues with some drivers in that they say one thing and do another. Similarly there was a major problem with how Windows Media Center coped with 16-235 content (you could end up with very washed out pictures as it tried to 'help') though there are registry settings (sometimes for drivers, sometimes for Win MC - depends on the setup) to sort this.

Haven't done it for a while to be honest - but there certainly were issues between HD and SD content (so you could get SD right and HD crushed, or HD right and SD sat-up in one situation)

Also - the set-up could switch depend on whether you're booted into Windows or OS X on your Mac - as the driver settings will potentially be different between OSs. (IME Macs are better at this though - as they are used every day in video editing 16-235 stuff)

It's REALLY annoying that even though 16-235 levelspace has been a standard since the very early 80s - and is used instead of 0-255 for very good engineering reasons (it avoids ringing caused by clipped overshoots and undershoots and accepts that analogue processes - and lots of broadcast TV signals still have analogue stages even in HD - are not perfect) - the handling of 16-235 video in Windows and PC drivers is woeful at times.
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