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• alsa-audio-dec : explicitly cast the delay to a signed int64

  1er décembre 2013, par Anton Khirnov

  alsa-audio-dec : explicitly cast the delay to a signed int64
  Otherwise the expression will be evaluated as unsigned, which will break
  
  when the result should be negative.
  
  CC:libav-stable@libav.org
  

  • [DBH] libavdevice/alsa-audio-dec.c

• libvpx : Cast a pointer to const to squelch a warning

  24 août 2016, par Diego Biurrun

  libvpx : Cast a pointer to const to squelch a warning
  libavcodec/libvpxdec.c:100:57 : warning : passing argument 3 of ’av_image_copy’ from incompatible pointer type
  
           av_image_copy(picture->data, picture->linesize, img->planes,
  
  libavutil/imgutils.h:116:6 : note : expected ’const uint8_t **’ but argument is of type ’unsigned char **’
  
   void av_image_copy(uint8_t *dst_data[4], int dst_linesizes[4],
  

  • [DBH] libavcodec/libvpxdec.c

• Correcting color cast with ffmpeg

  16 mai 2018, par Henry H

  I have two videos that have a pretty significant blue cast to them. I took some stills at the same time and I’m happy enough with the colors on those and I’d like to re-encode the videos, adjusting the colors to something similar to the stills.

  • A frame from the original video can be seen here : http://www.dotrose.com/temp/img_20180513_153484_original.png
  • An attempt at correcting the color, which would be acceptable : http://www.dotrose.com/temp/img_20180513_153484_corrected.png
  • A still image taken at the same time (but with some help from a flash) : http://www.dotrose.com/temp/img_20180513_153476.jpg

  I understand I could either create a large collection of jpg images from the video and color correct them before reassembling them into a new video or I could use ffmpeg’s color level’s filter to do it directly. What I don’t know is how to get the numbers to pass to the filter. I’m assuming I want to do something like this :

  ffmpeg -i video.mov -vf "colorlevels=rimin=##/255:gimin=##/255:bimin=#/255:rimax=###/255:gimax=###/255:bimax=###/255, eq=gamma=#.##" -y out.mov

  How do I get the values to use for each of the r, g, and b min and max settings and gamma to use in place of the ###s ? Assuming this is the right approach, of course.

  Update : Perhaps this question would be better asked in a forum for gimp or photoshop. But I know how to adjust the color in those. What I need to know is how I translate those changes to what ffmpeg is expecting.