[FFmpeg-user] V360 stabilization

[Paul B Mahol]

On Fri, Oct 02, 2020 at 07:59:12PM +0200, Michael Koch wrote:
> Am 02.10.2020 um 10:10 schrieb Paul B Mahol:
> > On Thu, Oct 01, 2020 at 11:40:57PM +0200, Michael Koch wrote:
> > > Am 01.10.2020 um 22:11 schrieb Paul B Mahol:
> > > > On Tue, Sep 29, 2020 at 10:54:54PM +0200, Michael Koch wrote:
> > > > > Hello all,
> > > > > 
> > > > > I've programmed a C# workaround for stabilization of 360° videos. The
> > > > > procedure is as follows:
> > > > > 
> > > > > 1. FFmpeg: From each frame of the equirectangular input video, extract two
> > > > > small images which are 90° apart in the input video. I call them A and B
> > > > > images.
> > > > > 
> > > > > 2. C# code: Analyze the x and y image shift from subsequent A and B images.
> > > > > Calculate how the equirectangular frames must be rotated (yaw, pitch, roll)
> > > > > to compensate the image shifts. This part wasn't easy. Two rotation matrices
> > > > > and one matrix multiplication are required. Write the results to a *.cmd
> > > > > file.
> > > > > 
> > > > > 3. FFmpeg: Read the *.cmd file and apply the rotations with the v360 filter.
> > > > > The output video is stabilized.
> > > > > 
> > > > > For details and source code please have a look at chapter 2.78 in my book:
> > > > > http://www.astro-electronic.de/FFmpeg_Book.pdf
> > > > > 
> > > > > If anyone wants to implement this in FFmpeg, please feel free to do it.
> > > > Better upload DNG files that do not decode with FFmpeg.
> > > In this message
> > > http://ffmpeg.org/pipermail/ffmpeg-user/2020-August/049681.html
> > > you find a link to many DNG images which FFmpeg can't decode correctly.
> > > There is no error message, but the result is much too dark with low
> > > saturation.
> > Use correct player like mpv, which does not ignore color_trc.
> 
> A player? The output is a jpg image and it's too dark.

Yes, player, ffmpeg is not correct in conversion. Because swscale is old
and ignores color_trc metadata that is required for correct display.

Use zscale instead for converting pixel formats.


> 
> ffmpeg -i input.dng output.jpg
> 
> 
> > > I did convert a RAW image from a Canon 6D to DNG with Adobe DNG Converter
> > > V12.4. FFmpeg is unable to decode this DNG image. See this message for
> > > details:
> > > http://ffmpeg.org/pipermail/ffmpeg-user/2020-August/049738.html
> > > You can download the DNG image here (I will delete it from my webspace in a
> > > few days):
> > > www.astro-electronic.de/IMG_3459.dng
> > > 
> > > I did also try a RAW image from a Canon 5D-MK4 with the same negative
> > > result.
> > > 
> > > A friend gave me a DNG image that was written by his Pentax K5 camera. Same
> > > negative result.
> > > 
> > > Summary: I did try DNG images from 4 different sources and in 4 of 4 cases
> > In my testcases, 30 out of 30 DNGs decoded just fine.
> 
> Did any of your 30 DNGs come from Adobe DNG converter V12.4, or from a
> Pentax K5 camera?

No, as that converter tends to create invalid DNG files.
But thanks for uploading only one DNG file, I added support for it.

> 
> Michael
> 
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