[FFmpeg-user] Contractor to help with filters

[Paul B Mahol]

On 12/31/19, Mark Filipak <markfilipak.windows+ffmpeg at gmail.com> wrote:
> 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
>>>>> _______________________________________________
>>>>> ffmpeg-user mailing list
>>>>> ffmpeg-user at ffmpeg.org
>>>>> https://ffmpeg.org/mailman/listinfo/ffmpeg-user
>>>>>
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There is normalize filter for RGB, and histeq filter for YUV.