fate: make lavfi tests output only md5

Instead of saving huge raw files, use the md5: output pseudo-protocol
to calculate the checksum of the file directly.  This is especially
useful when testing on remote targets as it avoids transferring 3.6GB
over the network.
(cherry picked from commit f4b1e21a6304cda58ac36401d8f8dec7ff61d056)

tests/lavfi-regression.sh

@@ -14,11 +14,20 @@ eval do_$test=y
 rm -f "$logfile"
 rm -f "$benchfile"
 
+do_video_filter() {
+    label=$1
+    filters=$2
+    shift 2
+    printf '%-20s' $label >>$logfile
+    run_ffmpeg -f image2 -vcodec pgmyuv -i $raw_src    \
+        -vf "$filters" -vcodec rawvideo $* -f nut md5: >>$logfile
+}
+
 do_lavfi() {
     vfilters="slicify=random,$2"
 
     if [ $test = $1 ] ; then
-        do_video_encoding ${test}.nut "" "-vcodec rawvideo -vf $vfilters"
+        do_video_filter $test "$vfilters"
     fi
 }
 
@@ -48,10 +57,7 @@ do_lavfi_pixfmts(){
 
     pix_fmts=$($showfiltfmts $filter | awk -F '[ \r]' '/^INPUT/{ print $3 }' | sort | comm -12 - $out_fmts)
     for pix_fmt in $pix_fmts; do
-        output=${test}-${pix_fmt}.nut
-        do_video_encoding $output "" \
-            "-vf slicify=random,format=$pix_fmt,$filter=$filter_args -vcodec rawvideo -pix_fmt $pix_fmt"
-        rm ${outfile}${output}
+        do_video_filter $pix_fmt "slicify=random,format=$pix_fmt,$filter=$filter_args" -pix_fmt $pix_fmt
     done
 
     rm $exclude_fmts $out_fmts
@@ -69,10 +75,7 @@ do_lavfi_pixfmts "vflip"   ""
 if [ -n "$do_pixdesc_be" ] || [ -n "$do_pixdesc_le" ]; then
     pix_fmts="$($ffmpeg -pix_fmts list 2>/dev/null | sed -ne '9,$p' | grep '^IO' | cut -d' ' -f2 | sort)"
     for pix_fmt in $pix_fmts; do
-        output=lavfi_pixdesc-${pix_fmt}.nut
-        do_video_encoding $output "" \
-            "-vf slicify=random,format=$pix_fmt,pixdesctest -vcodec rawvideo -pix_fmt $pix_fmt"
-        rm ${outfile}${output}
+        do_video_filter $pix_fmt "slicify=random,format=$pix_fmt,pixdesctest" -pix_fmt $pix_fmt
     done
 fi