Shell script that encodes an HEVC / H.265 `.mkv` movie with the highest possible quality

transcode-x265.sh

#!/bin/sh

# Helper script to transcode to high-quality x265 clips via ffmpeg
#
# Uses best possible settings with two-pass encode
# See below for additional options.
#

# File from which the video is taken
inputFile=$1

# File to which the final generated output video will be written
outputFile=${inputfile%.*}.x265transcoded.mkv

# Enable this if video is 640x480 or larger
#
# It allows decoders to decode single frames with up to 4 threads
# Might not be necessary for modern decoders (which simply decode
# 4 frames in parallel, thereby achieving the same without tiles.
#
: ${useFourTiles:=false}

# Bits per second to use for the video and audio streams
#
# For archiving, use double the input bitrate upped to next power of two
#    768 =  640 video + 128 audio
#   1024 =  896 video + 128 audio    1024 =  768 video + 256 audio
#   1536 = 1408 video + 128 audio    1536 = 1280 video + 256 audio
#   2048 = 1920 video + 128 audio    2048 = 1792 video + 256 audio
#   3072 = 2944 video + 128 audio    3072 = 2816 video + 256 audio
#   4096 = 3968 video + 128 audio    4096 = 3840 video + 256 audio
#                                    6144 = 5888 video + 256 audio
: ${videoBitRate:=2304k}
: ${audioBitRate:=260k}

# After how many frames to force a keyframe
#
# More keyframes worsen overall compression but allow better seeking.
# Many encoders recommend one keyframe per second, but one every two
# seconds is much more sensible imho.
#
: ${keyFrameInterval:=72}

#     ###      Careful, only enable one of the options below at a time.
#    ## ##     
#   ## | ##    If multiple -filter:v statements are passed to ffmpeg, it only
#  ##  '  ##   takes the first (or last?) one, so if multiple filters are needed,
# ###########  you have to manually combine the -filter:v statements into one.
#

# Set to crop the video
#
# Should be set to "width:height:offsetX:offsetY" if used
# Leave set to false in order to perform no cropping at all
#
: ${cropBoundaries:=false}

# Whether to sharpen the video
#
: ${sharpenVideo:=false}

# Whether to rescale the output to 1920x1080
#
: ${rescale1920x1080:=false}

# ----------------------------------------------------------------------------------------------- #

# Delete intermediate files from previous encodes if already there
#
if [[ -f ffmpeg2pass-0.log ]]
then
	rm ffmpeg2pass-0.log
fi

if [[ -f x265_2pass.log ]]
then
	rm x265_2pass.log
fi

if [[ -f x265_2pass.log.temp ]]
then
	rm x265_2pass.log.temp
fi

if [[ -f x265_2pass.log.cutree ]]
then
	rm x265_2pass.log.cutree
fi

if [[ -f x265_2pass.log.cutree.temp ]]
then
	rm x265_2pass.log.cutree.temp
fi

# ----------------------------------------------------------------------------------------------- #

ffmpegParameters=()

# If the user has specified cropping bounds, set up the respective
# ffmpeg parameters
#
if [ "$cropBoundaries" = false ]
then
	echo Cropping disabled.
else
	echo Cropping to $cropBoundaries
	ffmpegParameters+=(-filter:v crop=$cropBoundaries)
fi

# Rescale the output to 1920x1080 from whatever it had before and just claim
# the aspect ratio is 16:9. This is useful if the image was slightly off from
# 1920x1080 (i.e. 1912x1076) and you want it to avoid playback scaling
# (and the aspect ratio still matches or is off by very little!)
#
if $rescale1920x1080 ; then
	echo Rescaling to 1920x1080
	ffmpegParameters+=(-filter:v scale=1920x1080:flags=lanczos,setsar=16/9)
	ffmpegParameters+=(-sws_flags lanczos)
fi

# Apply a light sharpening filter over the video. This may help improve image
# quality when transcoding movies that are at a decent bitrate, but where
# the image has (from recording or studio-internal processing) sufferent a loss
# of sharpness. Doesn't do anything good to transcoded low-bitrate movies.
#
if $sharpenVideo ; then
	echo Sharpening enabled
	ffmpegParameters+=(-filter:v "smartblur=lr=2.0:ls=-0.5:lt=-3.5:cr=1.0:cs=-0.25:ct=-1.5")
fi

# ----------------------------------------------------------------------------------------------- #

# Video encoder settings
#
ffmpegParameters+=(-c:v libx265)
ffmpegParameters+=(-b:v $videoBitRate)
ffmpegParameters+=(-g $keyFrameInterval)

# We use the 'main' rather than the 'high' profile. The profile does
# not enable any advanced encoding technology, it merely switches between
# two lanes of allowed bitrates. For out goals, the 'main' profile is
# more than enough and isn't outright rejected by cheap TVs.
if [ "$tenBit" = true ]
then
	echo 10-bit encode
	ffmpegParameters+=(-pix_fmt yuv420p10le)
	ffmpegParameters+=(-profile:v main10)
else
	echo 8-bit encode
	ffmpegParameters+=(-pix_fmt yuv420p)
	ffmpegParameters+=(-profile:v main)
fi

x265Parameters=''

if [ "$useFourTiles" = true ]
then
	echo Experimental 4-slice encoding
	x265Parameters="slices=4:no-wpp=1:fps=$videoFps:ref=6:rd=6:rdoq-level=1:rect=1:amp=1:psy-rd=2.5:psy-rdoq=1.5:fades=1:hevc-aq=1:aq-motion=1"
else
	echo Single slice encoding
	x265Parameters="slices=1:no-wpp=1:fps=$videoFps:ref=6:rd=6:rdoq-level=1:rect=1:amp=1:psy-rd=2.5:psy-rdoq=1.5:fades=1:hevc-aq=1:aq-motion=1"
fi

# ----------------------------------------------------------------------------------------------- #

# Audio encoder settings
#

# No subtitles, no audio, nothing
#
# Audio should either be Opus (for PC playback) or AAC, encoded via QAAC and not
# by ffmpeg (for TV playback), so audio transcoding is simply disabled here.
# My workflow is to remux the transcoded H.265 video with QAAC-transcoded audio
# tracks in MKVToolNix after I have all the invidiual tracks transcoded.
#
ffmpegParameters+=(-an -sn -dn)

# This would transcode to Opus (for PC playback)
#
#ffmpegParameters+=(-c:a libopus)
#ffmpegParameters+=(-b:a $audioBitRate)
#ffmpegParameters+=(-ar 48000)

# ----------------------------------------------------------------------------------------------- #

# Other settings
#

# Use only 1 thread for encoding.
#
# This increases transcoding time to about 1 day per 2-4 minutes of movie but improves
# compression efficiency vs. multiple threads. So on a multi-core CPU, simply transcode
# a few movies in parallel, each with 1 thread and you'll lose no time overall.
#
ffmpegParameters+=(-threads 1)

# Parameters kept from other codecs, they probably don't translate to x265
#
#ffmpegParameters+=(-auto-alt-ref 1)
#ffmpegParameters+=(-lag-in-frames 25)
#ffmpegParameters+=(-quality best)
#ffmpegParameters+=(-deadline best)
#ffmpegParameters+=(-speed 1)
#ffmpegParameters+=(-cpu-used 0)
#ffmpegParameters+=(-frame-parallel 1)

# ----------------------------------------------------------------------------------------------- #

echo "ffmpeg options: ${ffmpegParameters[@]}"
echo "libx265 tuning: $x265Parameters"

echo ==========================================================================
echo ""
echo "Encoding first pass"
echo ""

ffmpeg \
	-hide_banner \
	-i "$inputFile" \
	-shortest \
	"${ffmpegParameters[@]}" \
	-preset veryslow \
	-x265-params "$x265Parameters:pass=1" \
	-pass 1 \
	-f null \
	/dev/null

echo ==========================================================================
echo ""
echo "Encoding second pass"
echo ""

# Second pass
ffmpeg \
	-hide_banner \
	-i "$inputFile" \
	-shortest \
	"${ffmpegParameters[@]}" \
	-preset veryslow \
	-x265-params "$x265Parameters:pass=2" \
	-pass 2 \
	-y \
	transcoded-x265.mkv