Rendering and levels

Satevis wrote on 6/15/2015, 5:00 AM

Actually, Vegas doesn't do anything with your levels unless you ask it to. It doesn't even do what the player software later does, which is why the (internal) preview looks different than YouTube etc. Pro: It shows you everything that's in your footage, even those parts a player would clip. Con: It looks different than the final result.

If this bothers you, have a look at my Preview Levels extension (http://www.semw-software.com/extensions/). It adds a switchable Levels filter to your video bus for preview and disables it automatically when rendering.

mark2929 wrote on 6/15/2015, 7:22 AM

Thanks Satevis

I'll install your program later and let you know how I get on!

Best,

Mark

Arthur.S wrote on 6/16/2015, 10:18 AM

I've been using your preview levels for a while now. Brilliant....wouldn't be without it now.

musicvid10 wrote on 6/16/2015, 3:25 PM

What Vegas versions does this plugin work with?
Had trouble finding sysreq on the download page.

vkmast wrote on 6/16/2015, 5:03 PM

See Compatibility tabs for SysReq.

Satevis wrote on 6/16/2015, 5:50 PM

Brilliant....wouldn't be without it now.

Thanks, I'm glad to hear that.

The extensions will work with Vegas 11 and up with the exception of Preview Levels. Vegas 11 seems to have issues with preset switching via the API, so Preview Levels requires Vegas 12 or 13 to work correctly.

Rich Parry wrote on 6/17/2015, 2:10 AM

Satevis,

I installed your Preview Levels extension. thanks.

I believe I understand the concept of Preview Levels, but how did you come up with the Level parameters. Is it an estimation or did you use specific values based on some industry standard parameters. I'm wondering just how accurate it is.

If you have time, a non-technical explanation of the PC vs. TV options would be appreciated.

When I have Preview Levels in the PC mode, should I expect my video to look like it will when displayed in a video player like VLC or on Vimeo and YouTube.

If my questions don't make sense, maybe I don't understand Preview Levels.

Thanks again,

Satevis wrote on 6/17/2015, 8:13 AM

Your questions make perfect sense, so here are a few more details:

The level values are indeed derived from industry standards such as the ITU-R Recommendation BT.709 (for HDTV) or BT.601 (for SDTV). For 8-bit coding, these standards place the black level at 16 and the nominal peak at 235. These translate to the normalized floating point values of 0.063 and 0.922 used in the "PC" preset.

The "PC" preset performs an exact conversion from studio RGB to computer RGB and should give you the most faithful conversion for DVDs or Blurays watched on a PC, web video, and probably most hardware players/TV combinations.

The "TV" preset is based on reports that some HDTV sets may reserve some headroom to actually differentiate between levels of superwhite. It, too, corrects the black point of the signal but will not clip values beyond 235. This will likely produce a slightly duller image than most playback environments. To account for that, it also includes a slight gamma correction. This gamma value is pure guesswork (and certainly depends on the individual TV set), so feel free to use your own value (or just stick with the "PC" preset).

What VLC displays depends on your settings there. If you target only your personal VLC installation and find that it does not currently do the studio-rgb-computer-rgb conversion, you can check the "Keep preview levels" options in the render dialog to keep Preview Levels active during rendering. Be aware, though, that this file will then most likely not display correctly in most other players.

monoparadox wrote on 6/17/2015, 1:19 PM

Satevis,

Is your plugin only compatible with 8 bit? How about with 32 bit? I've noticed some strange stuff when using 32 bit video levels.

--tom

Satevis wrote on 6/17/2015, 1:49 PM

Preview Levels uses the standard Sony Levels effect included in Vegas. I've been using it with both 8 and 32 bit projects for a while and so far haven't noticed any issues.

musicvid10 wrote on 6/17/2015, 2:12 PM

"
There are so many things one can do to screw up monitor / teevee levels, that I wouldn't try to anticipate or preemptively control them. For instance, with your additional TV headroom, and so many people having access to the dangerous "dynamic contrast" switch, levels could come out so flat as to be unwatchable in average room lighting. At least have the option to deliver unadulterated REC 709 Luminance without any additional gamma shift, for the folks who actually have correct screen levels.

Satevis wrote on 6/17/2015, 2:30 PM

Yes, I would definitely recommend using the standards-compliant "PC" setting unless you need to account for the peculiarities of one particular output device.

Rich Parry wrote on 6/17/2015, 2:35 PM

Satevis,

Thanks for the PC/TV preset explanation and the extension. Good stuff.

Rich

monoparadox wrote on 6/17/2015, 10:09 PM

I'd like to add my thanks, also.

-- tom

ushere wrote on 6/17/2015, 11:01 PM

hi satevis.

first, thanks for creating a free extension - they are always most welcome in vegas's toolkit...

however, i'm probably going to seem very dense with the following, but hey, i'm old enough to have forgotten what i learnt at the beginning of my vegas trip ;-)

if i put sony gen pal test bars on my tl my waveform / vector show 'correct' levels. if i switch to your 'pc' i see a rise in the bars, etc.,

a. if i need to cc should i be doing this with your 'pc' switched in or out?

b. 'pc' only affects preview and is not rendered as such?

btw. all my projects are distrib to net or flat screen (usually .mp4). i actually don't know anyone with a crt anymore ;-)

Marco. wrote on 6/18/2015, 3:00 AM

"This gamma value is pure guesswork."

Not really. It's a correction (to the Vegas Pro internal value of 2.2) based on the EBU technical paper for consumer flat panels which recommends a gamma value of 2.35 in dim-surround environment (EBU Tech. 3321).
The TV preset's gamma correction value should be close to precise as it's 2.354 in the end.

Satevis wrote on 6/18/2015, 5:22 AM

Marco., you're right. I forgot how you came up with the gamma value. The TV preset was your contribution, of course, so you'd be the one to ask for details on that one.

ushere, if you're using studio RGB clips on your timeline, then you should color correct in the "PC" setting. When using the video scopes, be aware that they refer to the image as displayed in the preview window, so their "Studio RGB" setting has to be turned OFF for "PC"/"TV" and "ON" for "Original".

Preview Levels will automatically disable the correction during rendering, so you don't need to switch back to "Original" before rendering. Should you ever want to include the correction in your rendered output (such as when rendering to JPEG oder WMV), there's a "Keep preview levels" option in the render dialog.

musicvid10 wrote on 6/18/2015, 7:44 AM

Actually, the screen gamma is 2.2, not the source.
To achieve linear viewing levels, internal gamma weighting is 1/2.2, or .454
I actually ran some tests to confirm this sometime back.

ushere wrote on 6/18/2015, 7:53 AM

thanks - very clear now ;-)

doublehamm wrote on 7/8/2015, 7:08 PM

Your extension intrigues me Satevis. I usually have no issue with using the "Adjust levels from studio RGB to computer RGB" in the preview device preferences, Then in the video scope sertting I select Studio RGB (16 to 235). Always look great on TV with those settings and keeping my waveform between 0 and 100.

First I assume I should uncheck these options while using your extension (otherwise it looks horribly crushed especially the blacks) and my scope meter has my blacks going way below -0- if I do not turn those off. So I did that.

Now I see PC and TV show a tad different in the waveform. Do I have that much more room on the high end if I am authoring to Blu-Rays for use in HD and UHD tvs (looking solely at the waveform)? Should I stay between 0 and 100 in the waveform this way?

Satevis wrote on 7/27/2015, 8:58 AM

Yes, while the extension is active, "adjust levels" should be disabled or the correction would be done twice on the external preview.

When using the waveform monitor, your settings there have to match your Preview Levels setting: If you're previewing in "Original" mode, your waveform has to be set to "Studio RGB" mode and will show excursions below 0 and above 100. If you're previewing in "PC" mode, your waveform's "Studio RGB" mode has to be disabled and any parts below 0 and above 100 will show as clipped lines.

I'm afraid there's currently no way to have both a corrected view in the internal preview and a waveform display that shows superblack and superwhite values, because the correcting and clipping of the signal happens before it reaches the waveform monitor.

The "PC" preset conforms to the Blu-ray standard, so you can't really expect anything not visible there to show up upon playback. The rationale behind the "TV" setting is that a certain amount of superwhite content gets encoded onto the finished blu-ray, so technically, a player/tv combination would be able to decode and display data beyond the nominal white level. If you notice that your configuration shows more highlight detail than is visible in the "PC" setting, then the "TV" setting, which doesn't clip the superwhites, may be closer to what you will see.