Rotate

If the camera was recording in "upside down" mode: 

parallel -u 'echo {}; jpegtran -rotate 180 -perfect -copy all -outfile {}.tran {} && mv {}.tran {}' ::: *.jpg

Resize & crop

   1 # Crop top
   2 find . -name '*JPG' -print0 | xargs -0 -P$(nproc) -n256 gm mogrify -chop 0x486 -resize 1920x1080
   3 # or Crop bottom
   4 find . -name '*JPG' -print0 | xargs -0 -P$(nproc) -n256 gm mogrify -gravity South -chop 0x486 -resize 1920x1080

For the GoPro HD Hero 2: 

   1 # Crop top
   2 find . -name '*JPG' -print0 | xargs -0 -P$(nproc) -n256 mogrify -crop 3840x2880+0+720 -resize 1920x1080

LDR tone mapping

parallel -u 'echo {}; ~/sys/tonemap/tonemapping ~/sys/tonemap/default.tnp {} {}.tonemapped && mv {}.tonemapped {}' ::: *.JPG

batch: 

for i in $(ls); do (cd $i; parallel -u 'echo {}; ~/sys/tonemap/tonemapping ~/sys/tonemap/default.tnp {} {}.tonemapped && mv {}.tonemapped {}' ::: *.JPG); done;

Encode to WebM

mencoder mf://*.JPG -mf fps=15:type=jpg -ovc lavc -oac lavc -of lavf -lavfopts format=webm -lavcopts threads=4:acodec=vorbis:vcodec=libvpx -ffourcc VP80 -o $(basename $(pwd)).webm

batch: 

for i in $(ls); do (cd $i; mencoder mf://*.JPG -mf fps=15:type=jpg -ovc lavc -oac lavc -of lavf -lavfopts format=webm -lavcopts threads=4:acodec=vorbis:vcodec=libvpx -ffourcc VP80 -o $(basename $(pwd)).webm); done;

Merge WebM files

After placing all the WebM files in one directory, merge with: 

f() { args=("$1"); shift; args+=("${@/#/+ }"); echo "${args[@]}"; }; echo mkvmerge $(f $(ls *webm))