[FFmpeg-user] Contractor to help with filters

[Mick Finn]

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 <oliver at revl.com> 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 <mikeshaffer at gmail.com>
> 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 <oliver at revl.com> 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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