I own a blackmagic intensity pro capture card. I'm still learning and was wondering if one could achieve a perfect uncompressed capture of some input.
This is my setup: Computer1 Nvidia output -> Computer2 Intensity pro hdmi input.
To the naked eye it looks uncompressed but when analysing pixels closely there is some noise or color differences.
Same results with both 720p@60 and 1080p@30. I tried with blackmagic media express and VirtualDub 1.10.4
I can spot those differences in a video captured with bm media express, and in the preview window of virtualdub (not even recording)
VirtualDub settings: Video -> Compression... -> "(No recompression: HDYC)"
Video -> Set custom format... -> Custom size 1920x1080 / Data format: HDYC YUV 4:2:2 interleaved (Rec. 701) (only working data format)
Does anyone have any idea about some options or else that would cause this?
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You're going to have to show us some examples of what you mean by "noise or color differences".
Your captures are always going to be 4:2:2 with this device, which means that colors will be 1/2 the resolution of the greyscale.
You may be viewing your caps with a rec.601 matrix rather than a rec.709 matrix. That will cause a shift in (mostly) greens and reds:
Even if you're using the correct matrix, if you're starting with RGB images you will lose accuracy by the conversion to YUV and colors will blur because of the chroma subsampling.
Thank you both for your help. Well I didn't know much about chroma subsampling until now. It's indeed the 4:2:2 subsampling that bothers me. Is there any card that will capture hdmi raw rgb input with 1080p@60 ? (4:4:4 I guess?).
I need at least yuv 4:4:4 for preview mode in virtualdub, not necessary in file capture mode.
Last edited by sanlyn; 19th Mar 2014 at 09:42.
Since you're recording from a computer you should try using screen capture software instead of hardware. That way you can get RGB 4:4:4, lossless.
Some of the Avermedia capture cards have HDMI input uncompressed (or losslessly compressed) capture. I don't know if they'll work in RGB.
The source is RGB (as set in the nvidia control panel) but my intensity pro card applies subsampling 4:2:2 and that's my issue. I want to display true RGB (4:4:4) under VirtualDub.
Is this project worth thousands of dollars to you?
And keep in mind that almost all final delivery formats are YUV 4:2:0.
Found this card (~300$) :http://www.timeleak.com.cn/en/article/view.php?ps_db=prod&pnid=2&ps_aid=18
*HDMI and component video: Up to 1080p/60Hz
*Maximal resolution of DVI: Up to1920*1080 60 Hz
(And by the way, dvi is fine too)
*Hardware color conversion, with output formats of RGB24, RGB32, YUY2, UYVY and I420
Capture Format : Color space: YUY2, UYVY,RGB24, RGB32, I420
Now this is a bit confusing to me. They state rgb24 as output option so that's what I'm looking for right? Although I read this on the virtualdub doc : "Guess how they produce RGB24 data when you ask for it? You guessed it, the YUV 4:2:2 data is upsampled to RGB24. This means that the extra color resolution that RGB24 gives is entirely fabricated."
So i'm wondering if this card auto applies yuv 4:2:2 conversion.. I emailed them..
Last edited by sanlyn; 19th Mar 2014 at 09:42.
unless you are creating RGB444 from scratch, i would ask, what could you possible have that is actually RGB444 that you need to capture it exactly that way over hdmi ? since any input video obtained through some capture devices will originate from YUV420 color sampling format, and even that will be internally processed to YUV422, which is what you will ultimately want to capture as your final destination file in this goal of yours. anyway.
like everyone else said, tipicle capture cards internally process the incoming source video to a finished uncompressed (raw) though sampled YUV 4:2:2 color format. from there, you have the choice to capture that as either:
so, the possibilities may include any of the following over composite/svideo/component/hdmi/sdi/dvi input connections to the capture device ...
input YUV420 -> process -> output YUV422
input YUV420 -> process -> output YUV422->RGB444*
input YUV420 -> process -> output YUV422->YUV420*
where in the case of "process" the capture device internally processes the video in 8,9,10, or 12bit. higher bit depth gives better quality.
* where the capture device is selected to produce rgb444, it will yuv422->rgb444.avi
or, if selected to produce yuv420, it will yuv422->yuv420.avi
i don't know any consumer cards that take a YUV422 as an input source, since vhs, laserdisc, dvd players, dvr recorders, satalite receivers, etc., etc., all output yuv420 only.
VirtualDub's documentation is super old, so that line is referring to analog capture cards. The card may be producing "fake" RGB, or maybe not. Customer testimonials for the Timeleak cards are hard to come by. Hopefully the company is able to respond with accurate info.
NTSC VHS isn't 4:2:0 either. It's an analog signal with roughly 2:0.1:0.1 resolution on a "4" scale.
In any case, it doesn't matter if the OP is capturing RGB from a computer. His source could well be 4:4:4.