CCIR-601 for DVD Burning?

discburn wrote on 12/26/2017, 3:40 AM

I have a 720p25 timeline with .m2t original footage. All edited and graded, ready to burn to disc.

For standard DVD, the video settings will be 720x576, 16:9, 25fps, Progressive.

But in the advanced settings, I see a dialogue box with a check box that says 'Brightness of output material corresponds with the CCIR-601 standard (video input has RGB 16-235)'. Should I check it or not?

As far as I know HD material is Rec709 and SD is Rec601. So a Blu-ray would be Rec709 and standard DVD Rec601.

I expect that if my timeline was SD, my DVD would have to be Rec601. Perhaps the check box is there in case the timeline is HD?

In my present scenario, my timeline is HD, and I've graded the material within 16-235 colour space. So should I tick the box to ensure those values translate correctly to DVD?

Most DVD players nowadays upscale to HD screens via HDMI. Are they decoding 601 to 709?

Any and all explanations of the 'Brightness of output material line...' very welcome!

See attached screen shot of dialogue box.

Comments

mschagen wrote on 12/26/2017, 4:24 AM

If your source material is hd, the check box should be off. If it is sd, the check box should be on. Any device which upscales SD should convert the colors also but they usually don't, leading to small color errors which usually go unnoticed.

Interesting read: http://www.glennchan.info/articles/technical/rec709rec601/rec709rec601.html

discburn wrote on 12/26/2017, 4:35 AM

Thanks mschagen!

While you're there, can you see the 'Noise Sensitivity' setting in the same dialogue box? It's set at '7', but I read somewhere that the default for digital material should be 4, and 8+ for analogue. Any comments on that?

Seamus

mschagen wrote on 12/26/2017, 5:04 AM

I think it is there to tell the encoder how much noise there is in the image to prevent it from wasting bits on trying to encode all that noise. The optimal settings really depends on your source material. Digital can also be very noisy. You should experiment with it. When the encoded video gets 'sticky', i.e. motion freezes here and there, the parameter is set to high, if you set it to low, you may see more compression artefacts especially when using low bitrates.

discburn wrote on 12/26/2017, 6:19 AM

Thanks again, mschagen! Much appreciated!

Seamus

Scenestealer wrote on 12/29/2017, 5:24 PM

MEP / VPX uses 0-255 colour space by default when editing, unless you go to Top Menu > Effects > Movie Effects Settings > Brightness /Contrast - and check Colour Space Correction, where it will apply a global setting to your project that will limit the colour space to 16-235 for any existing or subsequent colour / brightness adjustments you make to the project. If you do not do this then you can check the CCIR-601 box you mention in the Advanced (Main Concept) Encoder settings and achieve the same thing for you exported file and contrast will of course be reduced accordingly.

Re the Noise Sensitivity setting:-

I think it is there to tell the encoder how much noise there is in the image to prevent it from wasting bits on trying to encode all that noise. The optimal settings really depends on your source material. Digital can also be very noisy. You should experiment with it. When the encoded video gets 'sticky', i.e. motion freezes here and there, the parameter is set to high, if you set it to low, you may see more compression artefacts especially when using low bitrates.

It is not a matter of the encoder wasting bits but rather wasting time searching amongst the noise for movement / changes in macro blocks during Motion search.

If you increase this number then it should have little effect on the quality but could reduce the time to encode. On the other hand, if you video is very clean then reducing this number could increase the quality without greatly increasing the time.

The default for Noise Sensitivity used to be 4 in earlier versions of MEP /VPX using the Mainconcept encoder. Current versions have this set at 7, most likely to try to appease everyone's demand for a swift encode.

Peter

discburn wrote on 12/30/2017, 3:24 AM

Very interesting, Peter!

Because my programmes go to DVD disc, YouTube and Computer/Devices, I've opted for the 'safe' 16-235. I'm always working in Rec709, but stay with 0-255 scopes while visually keeping the waveforms between 16-235.

I always thought 601 and 709 were more 'different' than just colour space range (601 being for SD and 709 for HD)?

So the Colour Space Correction box, or the CCIR-601 Encoder box, clips the colour range for 'broadcast standard'? Regardless of HD or SD?

Seamus

discburn wrote on 12/30/2017, 3:55 AM

Just a follow-up observation...

In my VPX6, I've been playing with the Low Gamma setting to adjust the blacks and it doesn't seem to be able to lift them up without affecting the entire picture, ie making it way too bright.

I have a Flanders Scientific BM 210 screen and its Waveform Scope shows the bottom of the black touching 16, whereas on the VPX6 Waveform Scope it's 0.

The VPX6 whites (brightness) are closer to what the FS screen shows on its scope.

I'll test the blacks using the 'Lift' function in Davinci Resolve, see what that says and report back.

I've always had this problem with VPX6. Like it's calibrated at 16-235 but showing the 0-255, ie the black really is at 16 but showing at 0 on the Waveform Scope and actually stuck there.

Sorry, I wonder if this is now another topic??

Seamus

Scenestealer wrote on 12/30/2017, 4:15 AM

Hi Seamus

You would like VPX8 because it has an additional curves tool for adjusting the range. You can clearly adjust the top and bottom and create S curves by setting anchor points on a graph. I use it mainly for the black setting in conjunction with the RGB parade.

There was some discussion on the forum a year or two ago about the fact that the scopes seem to vary in different programs in what they say is zero. Maybe search the forum for things like 16-235 and CCIR-601 etc. by browj and johneb.

Peter

discburn wrote on 12/30/2017, 4:42 AM

Just revisiting the Gamma sliders in VPX6, I again realised that you can actually only adjust one, either High, Mid or Low. If you adjust one of them, and then click to adjust another, the setting is applied to the new mode!

I see a nice upgrade deal coming in for VPX9 which hopefully addresses that issue, as well as the curves you mention. I'll look through the forum too.

Seamus