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Proper 16-235 becomes 30-218 when uploaded on Youtube

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David StutzmannProper 16-235 becomes 30-218 when uploaded on Youtube
by on Dec 12, 2015 at 4:55:01 pm

Hello everyone,

I’m new to color management and after one week of watching tutorials, searching forums and running tests, I feel completely lost.

I use After effect and Premiere pro on Windows 7.

I color corrected my video in premiere pro, which uses a 0-255 luma range if I’m correct.
Then I export it as H264 .mp4, import it in After Effect and set the color space to Rec. 709 (16-235). I rectify the contrast a little bit, save and use Media encoder to encode the video as H264 .mp4. When I watch it with Media Player Classic, it looks exactly as in the preview so everything is ok so far.

At that point, here are the specs of the video:

Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 3 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 2s 0ms
Bit rate : 63.8 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 25.000 fps
Standard : PAL
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.003
Stream size : 15.6 KiB (15%)
Language : English
Encoded date : UTC 2015-12-12 13:50:35
Tagged date : UTC 2015-12-12 13:50:35
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

However, when I try to upload it on Youtube, pure black, which was 16, becomes 30 and pure white, which was 235, becomes 218.
So my guess is that either Youtube doesn’t care which color space you used and crops everything to 16-235, even if it’s already been done ; or I missed something and failed to have youtube recognize that my video was already at a legal color format.

Which brings me to a second point : if youtube scales everything to 16-235 then how can this person’s t-shirt be more than black (level 1, when it should logically be 16 !!!) :





What do you think?

Thanks.


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Chris WrightRe: Proper 16-235 becomes 30-218 when uploaded on Youtube
by on Dec 13, 2015 at 5:18:48 am

the missing puzzle piece is that youtube doesn't support color management in the first place. I recommend burning in the 16-235 with utility profile converter and turning off color management altogether for web uploads.


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Ivan MylesRe: Proper 16-235 becomes 30-218 when uploaded on Youtube
by on Dec 13, 2015 at 10:05:26 am
Last Edited By Ivan Myles on Dec 13, 2015 at 11:35:06 am

Welcome to the forum and thank you for including detailed information in your post. The root cause might be related to your AE color management settings, but there are several issues with your workflow.

• What format are your captured (source) files? If Premiere Pro is having trouble injesting, consider transcoding to a standard intermediate format based on a 422/444 10-bit all-intra codec such as ProRes, DNxHD/MXF, AVC-I, or Cineform. If the source files are 8-bit RGB then PNG or JPEG2000 image sequences will also work.


[David Stutzmann] "I color corrected my video in premiere pro, which uses a 0-255 luma range if I’m correct."

• Using Premiere Pro for color correction is fine. Although its settings are presented as 8-bit RGB the internal color processing supports RGB or YCC (YUV) at up to 32-bits depth per channel. Check that all effects support your preferred color pipeline, otherwise Premiere Pro might be processing internally as 8-bit RGB.

• The first priority is making sure the RGB channels are within 0-255, and this shouldn't be a problem if your source footage was captured from an 8-bit RGB display. Use the YC Waveform, RGB Parade, and Vectorscope video scopes when setting color levels. If the source footage is YCC, make sure the Y and RGB channels are within 0-100 IRE on the scopes. In practice, I like to set peak luminance around 90-92 IRE to have enough headroom to keep the peak RGB levels under 100 IRE.

• Are you checking the footage to make sure levels look good throughout each clip? Sections of video that are all black or desaturated are likely caused by settings made earlier. Use multiple keyframes to manage levels through the entire duration of each clip.


[David Stutzmann] "Then I export it as H264 .mp4, import it in After Effect and set the color space to Rec. 709 (16-235)."

Going to After Effects might be unnecessary and H.264 definitely is a poor choice of intermediate codec. H.264 is a high compression delivery codec. You are losing a lot of color information when exporting with 4:2:0 color subsampling. This results in a loss of detail and increases the likelihood of color blocking and banding. Use a Dynamic Link between AE and Premiere Pro or export an intermediate file in one of the formats listed above. If you are just tweaking contrast, though, try to do it in Premiere Pro and avoid the extra step to AE.


[David Stutzmann] "here are the specs of the video:

Bit rate : 63.8 Kbps
Bits/(Pixel*Frame) : 0.003"


• That's a problem. What export settings are you using? YouTube typically compresses to 0.07 bits/pel. I recommend uploading files at 0.20-0.40 bits/pel for best results. That correlates to 4.4-8.8 Mbps target bitrate for a 1280x720 25fps file. Set maximum bitrate to 1.5X-2.0X target and use 2-pass VBR encoding.


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Walter SoykaRe: Proper 16-235 becomes 30-218 when uploaded on Youtube
by on Dec 14, 2015 at 3:18:59 am

[David Stutzmann] "Then I export it as H264 .mp4, import it in After Effect and set the color space to Rec. 709 (16-235)."

You should not have to manually limit your range. Try skipping this step.


[David Stutzmann] "Which brings me to a second point : if youtube scales everything to 16-235 then how can this person’s t-shirt be more than black (level 1, when it should logically be 16 !!!) : "

Video levels are supposed to be scaled back to full levels on playback with a full-level display.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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David StutzmannRe: Proper 16-235 becomes 30-218 when uploaded on Youtube
by on Jan 10, 2016 at 1:47:23 pm

Thank you for all your answers. I finally understood what was wrong.

First, I understood that a video IS not "16-235" or "0-255" in absolute but rather "optimized for a display in 16-235 (or 0-255)".

So in premiere pro, I saw my video in a 0-255 space and it looked good. But I realized that my blacks were not always set to 0 so when the video was cropped to 16-235 on youtube, the blacks were too grey. The problem was solved by adjusting luminance and bringing the blacks to 0.

And I did not actually have a problem with "super whites" or "super blacks" since Premiere Pro cuts them off. So when the video was displayed in a 16-235 space, nothing when out of this range unlike in the video I posted in the first message.


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