93 lines
3.6 KiB
Bash
93 lines
3.6 KiB
Bash
#!/usr/bin/env bash
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# Re-encodes the video using a constrained bitrate/output size. If you want to
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# To target the visual quality with a variable bitrate, use trim-video-vbr
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if which tput >/dev/null 2>&1; then
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ncolors=$(tput colors)
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fi
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if [ -t 1 ] && [ -n "$ncolors" ] && [ "$ncolors" -ge 8 ]; then
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RED="$(tput setaf 1)"
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GREEN="$(tput setaf 2)"
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YELLOW="$(tput setaf 3)"
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BLUE="$(tput setaf 4)"
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MAGENTA="$(tput setaf 5)"
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CYAN="$(tput setaf 6)"
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BOLD="$(tput bold)"
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NORMAL="$(tput sgr0)"
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else
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RED=""
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GREEN=""
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YELLOW=""
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BLUE=""
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MAGENTA=""
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CYAN=""
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BOLD=""
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NORMAL=""
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fi
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filename=$(basename -- "$1")
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output_name="$2"
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target_bitrate_mb="$3"
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start_time="$4"
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end_time="$5"
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if [[ $filename == "" || $output_name == "" || $target_bitrate_mb == "" || $start_time == "" ]]; then
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printf "${BOLD}${RED}Usage: trim-video <filename> <output name> <target bitrate in MB, e.g. 6> <start time HH:MM:SS> <optional: end time HH:MM:SS, use empty string or 0 for no value>${NORMAL}\n"
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exit 1
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fi
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extension="${filename##*.}"
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filename="${filename%.*}"
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output="${output_name}.$extension"
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# bufsize is typically double the maxrate
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bufsize=$((target_bitrate_mb * 2))
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bufsize="${bufsize}M"
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bitrate="${target_bitrate_mb}M"
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timing_args=""
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if [[ $start_time != "" ]]; then
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timing_args="-ss $start_time "
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fi
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if [[ $end_time != "" ]]; then
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if [[ $start_time == "0" && $end_time == "0" ]]; then
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# We treat a start and end with 0 values as no op.
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timing_args=""
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elif [[ $end_time != "0" ]]; then
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# Handle having a start time but end time is set to 0, can just ignore it and it'll use the remainder of the video.
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timing_args+="-to $end_time"
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fi
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fi
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printf "\n${YELLOW}${BOLD}Trimming '$filename.$extension' | output: $output | start: $start_time | end: $end_time | max rate: $bitrate | buffer size: $bufsize ${NORMAL}\n"
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# You might have issues if the file has multiple video streams or embedded
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# subtitles. The -map 0 arg is typically given when copying a video stream, but
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# I'm not sure if it's appropriate to use here. If you want to target one of
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# the video streams then use `-map 0:v:0` and if you want to re-encode
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# subtitles then include `-c:s mov_text` with either of the `-map` args.
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# -preset 3 and 4 are the fastest on my 3080 and have the same output file
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# size. p3 seems slightly faster. Apparently 7 is the best for 30 series
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# according to chatgpt (lol) but it was slow and compressed.
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# -accurate_seek doesn't seem to be needed when -ss is after -i, only when -ss
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# is before -i. Having -ss after is apparently a way of enabling accurate
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# seeking. The catch is that if the trim doesn't start at 0, it can be a long
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# wait before the encoder gets to the portion you want to start trimming from.
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# To speed this up we are putting -ss and -accurate_seek before -i ... the
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# video duration might be slightly off from this but so far I haven't seen any
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# seeking issues. If they come up then we can move -ss to after -i again and
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# delete -accurate_seek.
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# I'm using -b:v, -maxrate:v, and -bufsize:v to constrain the bitrate and
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# indirectly control quality. The bitrate won't be fixed exactly to -b:v
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# unless using CBR, but NVENC will attempt to average around it and cap the
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# bitrate at -maxrate:v, using -bufsize:v as a smoothing buffer.
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ffmpeg -y -stats -loglevel level+error -hwaccel cuda -hwaccel_output_format cuda $timing_args -accurate_seek -i "$filename.$extension" -c:v h264_nvenc -profile:v high -preset 3 -b:v $bitrate -maxrate:v $bitrate -bufsize:v $bufsize -c:a copy -movflags +faststart "$output"
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printf "\n${GREEN}${BOLD}Finished trimming${NORMAL}\n\n"
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