[FFmpeg-user] V360 stabilization

[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.

> 
> 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.

> FFmpeg failed.
> 
> Michael
> 
> 
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