[HELP] ProRes 422 HQ -> 8-Bit PNG -> x264 -> Problem with colors

[TR2N]

Hi there,

i have a ProRes 422 HQ master that i have exported in a PNG 8-Bit image sequence. But as soon i choose Images as input in Hybrid and start the test encodes the picture itself gets darker than the original. The ProRes master is basing on a PAL DVD (BT.601 colour space) that i have deinterlaced with Hybrid / QTGMC, encoded as ProRes 422 HQ. I feed this master in VEAI and do the export as mentioned above. The PNGs itself looks good, but as soon i do the encode to x264 the problem with the levels occur. I tried some color space settings but i have no luck, maybe my noob knowledge is just to limited.

Can i avoid this level drop? When i export as ProRes 422 HQ out of VEAI and encode the result to x264 it works perfect and the picture is not altered.

Thank you and kindly regards!

[Selur]

Don't care about VEAI and since it's not open source or free that information does not help in any way.

My guess is:
You are probably not selecting the right values for 'Luma range' and 'Color matrix' that fit your input in the 'Image sequence selection' dialog.
Side note: bt.601 <> bt470bg and assuming you properly extracted the images the luma range should be limited since DVD content is limited range.


Cu Selur

[TR2N]

Don't care about VEAI and since it's not open source or free that information does not help in any way.

My guess is:
You are probably not selecting the right values for 'Luma range' and 'Color matrix' that fit your input in the 'Image sequence selection' dialog.
Side note: bt.601 <> bt470bg and assuming you properly extracted the images the luma range should be limited since DVD content is limited range.


Cu Selur

Hi Selur,

i know that you do not care about VEAI, i know the discussions on other boards. But for me, and i am a noob who want to learn and understand that kind of stuff, it is useful. Not everyone does have the knowledge about the rocket science video encoding could be. For me it is just a starting point before i am trying to learn doing it the pro way using Hybrid for example. 

Okay, i will check it out with the 'Luma range' and 'Color matrix' settings, maybe i have overseen something. One thing i don´t understand - do i have to choose the value the original source had, in my case the DVD (BT.601/BT470bg) and TV (limited range) in the 'Image Sequence selection' dialog? Even when my deinterlaced and mild filtered master was encoded to ProRes 422HQ using Hybrid and processed in VEAI to PNG8?

Thank you Selur!

[Selur]

The images do not contain headers which would tell Hybrid whether they use limited or full range or what color matrix should be used.
If you import an image sequence (images are in RGB) you need to tell Hybrid which LumaRange and ColorMatrix it should use to concert between RGB and YUV.

master was encoded to ProRes 422HQ using Hybrid and processed in VEAI to PNG8

If the colors are still okay in the ProRes 422HQ from Hybrid, the question is what VEAI does with the input and how it converts the prores file to PNG.
I have no clue whether VEAI uses the BT.601/BT470bg color matrix and limited luma range, or whether it may be always assumes the source is full range and uses bt.709 one something else. It might assume a specific color matrix depending on the input resolultion.
My guess is that VEAI always assumes limited-range (which is bad if the input isn't limited range) and bt601/bt470b color matrix (which is bad if the input uses bt709), but I don't know for sure and can only guess.

do i have to choose the value the original source had, in my case the DVD (BT.601/BT470bg) and TV (limited range) in the 'Image Sequence selection' dialog?

Yes, you have to set those values, but since I have no clue what VEAI does I can't recommend anything other than: Try&See which values work.


Cu Selur

[TR2N]

The images do not contain headers which would tell Hybrid whether they use limited or full range or what color matrix should be used.
If you import an image sequence (images are in RGB) you need to tell Hybrid which LumaRange and ColorMatrix it should use to concert between RGB and YUV.

master was encoded to ProRes 422HQ using Hybrid and processed in VEAI to PNG8

If the colors are still okay in the ProRes 422HQ from Hybrid, the question is what VEAI does with the input and how it converts the prores file to PNG.
I have no clue whether VEAI uses the BT.601/BT470bg color matrix and limited luma range, or whether it may be always assumes the source is full range and uses bt.709 one something else. It might assume a specific color matrix depending on the input resolultion.
My guess is that VEAI always assumes limited-range (which is bad if the input isn't limited range) and bt601/bt470b color matrix (which is bad if the input uses bt709), but I don't know for sure and can only guess.

do i have to choose the value the original source had, in my case the DVD (BT.601/BT470bg) and TV (limited range) in the 'Image Sequence selection' dialog?

Yes, you have to set those values, but since I have no clue what VEAI does I can't recommend anything other than: Try&See which values work.


Cu Selur

:-) Okay. I will try it with some test encodes. Will report when i found out what to set.