On Thu, Nov 4, 2021 at 9:41 AM Tom Vercauteren <tom.vercaute...@m4x.org> wrote:
> > > Apologies for cross-posting a question I initially posted on > stackoverflow > > > ( > > > https://stackoverflow.com/q/69739665/17261462) but having had no > response > > > there I thought this mailing list may be a better place for it. > > > > > > I am trying to encode 10 bit images losslessly in a video format. The > > > images are stored as 16 bit png files (but only use 10 bit - currently > the > > > least significant ones) and I have been working with ffmpeg to create > and > > > read back the video files. > > > > > > My best attempt so far is based on > > > https://stackoverflow.com/a/66180140/17261462 but as mentioned there, > I > > > get > > > some pixel intensity differences which may be due to rounding when > > > converting between 10 and 16 bit representation. I tried a few > different > > > means (bit shifting, left bit replication, floating point based > scaling) > > > but haven't yet figured out how to get a trully lossless > reconstruction. > > > > > > Below is a small piece of python code to replicate my issue. I > probably am > > > doing something wrong there so feedback would be appreciated. > > > > > > > > Upload input png somewhere? > > > > I guess that png files use only first 10bits from least significant bit. > > Thanks Paul. The python snippet I provided was creating the png on the > flies but for convenience I am attaching here an example 16bit png > that uses all least significant 10bits. I also provide alternative > versions using either the 10 most significant bits, rescaling the > intensities with > ROUND(input * MAXOUTSAMPLE / MAXINSAMPLE > or using left bit replication > (http://www.libpng.org/pub/png/spec/1.1/PNG-Encoders.html). > > For eae of use, here are also the ffmpeg commands in plain text and an > comparison with imagemagick so as to avoid the need for python. > > You can always store it into rawvideo (without any headers) and than interpret it as 10bit with specifying ffmpeg rawvideo demuxer parameters. > Encoding: > ffmpeg -y -i gradient10bit-scaledto16bits.png -c:v libx265 > -x265-params lossless=1 -pix_fmt gray10be > gradient10bit-scaledto16bits.mkv > > Decoding back to png: > ffmpeg -y -i gradient10bit-scaledto16bits.mkv -pix_fmt gray16be > recons-gradient10bit-scaledto16bits.png > > Comparison: > magick compare -verbose -metric mae gradient10bit-scaledto16bits.png > recons-gradient10bit-scaledto16bits.png diff-scaledto16bits.png > > Best wishes, > Tom > _______________________________________________ > ffmpeg-user mailing list > ffmpeg-user@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". > _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
