[FFmpeg-user] Contractor to help with filters

[Mark Filipak]

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 <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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