Is your application real-time?
On 12/30/2019 10:32 PM, Mick Finn wrote:
You need some rule based / AI processing to determine ‘bad lighting sections’ -
if you achieve would be viable commercial product.
Does ffmpeg have histogram and histogram equalization features?
Blindly doing histogram equalization on entire sequence might actually work
depending on content.
Sent from my iPhone
On Dec 31, 2019, at 6:58 AM, Oliver Dain <[email protected]> wrote:
Hi Michael,
Thanks for the suggestion. I'm not sure what your suggesting would work for
us. Lets say we have a video that's 5 minutes long and there's a 5 second
segment somewhere in the middle that needs its levels adjusted. If we used
your solution we'd adjust the entire video so the 5 seconds that was bad
would now look good but the rest of the video would look worse. We're
producing hundreds and hundreds of videos per day and the segments that
need adjusting are different for each video so manually finding the time
offsets where curves should be applied isn't possible (to say nothing of
finding the appropriate curve for each video).
What we need is a solution that analyzes the video to detect when frames
are dark and then lightens only those frames. What I think we need is
something like the "pp=autolevels" filter but I haven't had much luck with
that.
Thanks,
Oliver
On Mon, Dec 30, 2019 at 3:24 PM Michael Shaffer <[email protected]>
wrote:
Issues 1 and 2 would be pretty simple to fix. I would use Adobe Photoshop
create a "curves" layer which can then be exported as a .crv file. The .crv
file can be loaded by ffmpeg and applied to the image. Adobe Photoshop has
an auto-adjust button which gets it close, then you can tweak the
individual RGB values. That is how I eliminate atmospheric haze in real
time on my live cam. Here's a view of how it looks:
https://www.youtube.com/watch?v=_ixjB6dKsgk
I'm not sure about how you would auto detect changes in the
brightness/contrast. I know OpenCV can do that by calculating a histogram
of the entire image. I'm not sure if ffmpeg can do that or not since I've
never needed to do that.
Michael
On Mon, Dec 30, 2019 at 4:52 PM Oliver Dain <[email protected]> wrote:
Hi ffmpeg-users,
My company, revl.com, has several videos that could be improved. We've
played around with ffmpeg filters and haven't had much success. We're
hoping to find a contractor who can help. This would be a paid contract
probably lasting about a week.
Specifically we have 4 types of issues:
1. Sections of video that are too dark due to back-lighting
2. Sections of video that are too dark due to general low-light levels
3. Bits of video that are shaky
4. Videos that generally look OK but could look even better with
different
saturation or contrast settings.
Ffmpeg provides a lot of filters and each filter can take a variety of
configuration options. What we're hoping to find is a set of filter
configurations (e.g. a string passed --filter-complex) that will improve
our footage. These filters need to be configured to automatically detect
frames that exhibit the issue; applying a filter at specific manually
determined time points is not sufficient. It is OK to tell ffmpeg which
parts of the video frame to use for determining proper light levels
however.
If you're interested please reply directly to me and we can setup a quick
video chat to discuss the project in detail.
Thanks,
Oliver Dain
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