what engine did you use?
Please find the difference between Engine 1 and the others (Ultimate, Crystal and Engine 2) in sense of color space.
Both the “Ultimate” and “Crystal” engines seem to produce the same result with regards to the color conversion. I couldn't get the other two engines to work with one of the files I have to inventory, which are hundreds of AVI files with the “GAVC” video codec and no audio (CCTV type of footage) ; I installed CCCP as advised, still not working.
But I could get them to work with a more conventional MP4/H.264 video, see below.
Meanwhile I will have a look into Bt.601 and Bt.709. The difference looks almost negligible. Never thought that is important.
Anyhow, I will check if I can improve the conversion.
The difference is quite conspicuous on all-red or all-green areas : on my sample pictures, look at the green sign on the upper left, and the red packages of cakes in the middle.
I made further tests with a personal video (1280x720 MP4 H.264, purposefully created with the Bt.709 color conversion matrix in an Avisynth script encoded with MeGUI, as advised on this VideoHelp thread
), showing near the begining a still picture which I took of a red car, so I could accurately compare the screenshots with the original still picture. I found out that the colors were correct with “Engine 2” (at least with this particular 1280x720 video).
Doing that I also discovered a discrepancy in the way each engine interprets the timecodes when they are defined manually in the “specific time” field.
– Scorp Movie Thumbnails Maker, “Ultimate” module, specific time start 4s end 7s step 3s :
=> The colors are wrong (see still picture below).
– Scorp Movie Thumbnails Maker, “Engine 2” module, specific time start 4s end 7s step 3s :
=> With the same “specific time” parameters, it shows different frames, at 00:02 and 00:05 instead of 00:04 and 00:07 as requested. The colors are correct (the car's painting is displayed in the correct shade of red, the green leaves in the background are displayed in the correct shade of green).
Engine 1 shows the same frames (with the same parameters) but with shifted colors as above with “Ultimate”.
– Scorp Movie Thumbnails Maker, “Crystal” module, specific time start 4s end 7s step 3s :
With the same “specific time” parameters, it shows different frames yet again (different from “Engine 1” / “Engine 2” and also from “Ultimate”), yet the timestamps are the same as with “Ultimate” (this is a portion of video showing still pictures in rapid succession, so even a slight discrepancy is clearly visible). I couldn't get the “Crystal” module to show the same tiles as the first test above (it would require a better precision than 1s in the “specific time” field, VCSI accepts milliseconds as input, allowing to set times very accurately, which was useful here since VCSI showed a different second image with a 1s granularity, i.e. with 00:00:07 or 00:00:08), but from the previous tests I made, I guess that the results would be the same as with “Ultimate” (i.e. wrong colors for Bt.709 “HD” footage).
– Scorp Movie Thumbnails Maker, “Engine 1” module, specific time start 5s end 8s step 3s :
=> With different “specific time” parameters I could get the same tiles with “Engine 1” as with the first test using the “Ultimate” module (i.e. showing the same source still pictures, not necessarily the exact video frames) ; the colors are wrong.
– Scorp Movie Thumbnails Maker, “Engine 2” module, specific time start 5s end 8s step 3s :
=> Same tiles as above (“Engine 1” and “Engine 2” seem to interpret the “specific time” parameters identically), but the colors are correct (again, search for the reds and greens).
– VCSI (tweaked by adding "-vf", "zscale=matrixin=709:matrix=709,format=rgb24",
to each ffmpeg
call in the script, this switch was suggested in this VideoHelp thread
) with the parameters -g 2x1 (grid) -w 2560 (width) -m 0:00:05s,0:00:07.200 (manual timecodes) :
=> The colors are correct.
– Original still picture of the red car for comparison (just resized by 50%, no shift in colors compared with the straight-out-of-camera original) :
For clarity, I selected three of the pictures linked above to display directly at the end of this post :
– Scorp Video Thumbnails Maker “Ultimate” (wrong colors – same with “Engine 1” and probably “Crystal”) :
– Scorp Video Thumbnails Maker “Engine 2” engine (correct colors) :
– Tweaked VCSI script (correct colors – the native VCSI would show the wrong colors) :