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Adobe Premiere Pro like Re Mida?
Hi all,
I have recently captured some Betacam SP tapes using a BCB65 Pal with SDI onboard interface through Decklink and Decklink Pro.
As my primary interest was capturing at best quality, I used 10bit 4:2:2 declink preset within Adobe Premiere 1.5.1
As I need a better quality than 16bit 48Khz and my SDI interface is video only, I captured video using SDI and analog audio through external interfaces.
After coupling the audio and video track with Premiere and trying to extract frames for publishing purposes, I realized that superwhite gamma was lost during rendering process. I mean that, while the original captured videos are reproduced correctly by Decklink composite out (Y) with all shadings of white, the rendered video (using the same 4:2:2 codec) had lost the shadings on the bright areas.
The preview on the PC monitor also shows a flattened gamma.
If you want to check this, compare the output produced by simply reproducing the file captured with Decklink capture application and or within Premiere 1.5 with the one rendered by Premiere with 4:2:2 10bit settings, watching at the video monitor connected to analog out of the card.
Later I downloaded Photoshop and Adobe Premiere CS from Adobe and realized that it was impossible to preserve the original gamma doing whatever operation, including capturing.
Only capturing with Adobe Premiere 1,5, the gamma is preserved at least on the captured file when reproduced without rendering.
Capturing with Abobe Premiere Pro CS and Decklink uncompressed settings 10bit 4:2:2, the gamma is lost during capture, so Adobe Premiere CS is unusable also for capturing.
Practically, whatever calculation after decoding performed by Premiere (or Photoshop CS extracting frames) has the effect of flattening the near white areas and the material becomes unusable like the food touched by Re Mida.
I tried various settings under Premiere Pro 1.5 and Premiere CS and found that one way is good to preserve all levels of brightness is to capture with Decklink capture or Adobe Premiere 1.5 (not CS).
The serious problem is that it is not possible to cut or edit the captured video with Premiere because his calculations are wrong as they are involved in whatever operation like saving the file even with the same codec used during capture.
I found only one working method:
1) capturing video with Premiere 1.5 or Decklink capture application (not Premiere Pro CS).
2) Edit the file
3) Save the file using Adobe Premiere PRO CS and Microsoft uncompressed AVI setting with 10bit 4:2:2 video renderer.Practically you need both Premiere 1.5 and Premiere Pro CS, the first one for capturing, the second for rendering/saving.
In one occasion, I was also able to preserve gamma rendering with some sort of UYVY codec, but I could not replicate the experiment.
After that, I tried other settings and I discovered a very simple way to show the Re Mida effect.
It is enough adding whatever effect on the clip on the timeline and the gamma is suddenly flattened (even doing nothing on the effect’s settings).
Probably it is due to RGB/YUV colorspace conversion that is applied as soon as you ask something to Premiere’s rendering engine.
Please remember to watch at the analog out of the card not at the PC monitor, otherwise you will not see any difference because the RGB gamma on the computer monitor is always flattened.
You should also use a videoclip with very bright areas, near pure white to see the difference.
A sky with clouds is very good for this purpose.
Probably I will upload some avi files on our website and photos taken from the analog video monitor.
I will test the SDI output using HDLink soon.
I suppose this is the reason why Cineform intermediate codec or others are so used. I do not know if they work with SD material, but probably they could overcome Premiere’s limitation.
Please let me know your opinions about that.
Best regards,
Pier Mat
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