A/V Synchro-Test video generator using ffmpeg

.gitignore

*.mp4
overlay.png

generate.sh

#!/bin/bash
set -euo pipefail

[ -f overlay.png ] || {
	echo -e "\e[31mMissing overlay.png - loading generic image\e[0m"
	curl -sSfLo overlay.png "http://www.clker.com/cliparts/2/9/6/d/11971231361344964261JPortugall_icon_speaker.svg.hi.png"
}

vcodec=${VCODEC:-libx264}
fps=${FPS:-30}
length=${LENGTH:-60}

lowfreq=${LOW_FREQ:-1046}
highfreq=${HIGH_FREQ:-2093}
beepvol=${BEEP_VOL:-80}

filters=(
	# Audio (low beep)
	"sine=f=1:b=${lowfreq}:d=1[beeplow]"
	"[beeplow]bandpass=f=${lowfreq}:t=h:w=250[beeplow]"
	"[beeplow]bandreject=f=1:t=h:w=250[beeplow]"
	"[beeplow]volume=volume=${beepvol}[low]"
	"[low]asplit=3[low1][low2][low3]"

	# Audio (high beep)
	"sine=f=1:b=${highfreq}:d=1[beephigh]"
	"[beephigh]bandpass=f=${highfreq}:t=h:w=250[beephigh]"
	"[beephigh]bandreject=f=1:t=h:w=250[beephigh]"
	"[beephigh]volume=volume=${beepvol}[high]"

	# Audio (beep low left, 0ms)
	"[low1]stereotools=balance_out=-1[lowleft]"

	# Audio (beep low right, 1000ms)
	"[low2]stereotools=balance_out=1[lowright]"
	"[lowright]adelay=1000|1000[lowright]"

	# Audio (beep low both, 2000ms)
	"[low3]adelay=2000|2000[lowboth]"

	# Audio (beep high both, 3000ms)
	"[high]adelay=3000|3000[highboth]"

	# Audio combined 4s loop
	"[lowleft][lowright][lowboth][highboth]amix=inputs=4[audio]"
	"[audio]aloop=loop=-1:size=44100*4[audio]"

	# Split out audio for visualization
	"[audio]asplit[audio]"

	# Audio visualization (freqs)
	"[audio]showfreqs=s=1920x400:cmode=separate:fscale=log[audiovisual]"

	# Video background
	"color=color=0x333333:size=1920x1080:rate=${fps}[bg]"
	"color=color=0xf2f2f2:size=10x50:rate=${fps}[slider]"
	"[0]scale=height=250:w=-1[overl]"
	"[bg][overl]overlay=x=(main_w-overlay_w)/2:y=100[bg]"
	"[bg][audiovisual]overlay=x=(main_w-overlay_w)/2:y=main_h-75-overlay_h[bg]"

	# Draw slider with box and markings
	"[bg]drawbox=x=20:y=500:h=50:w=1880:color=white[bg]"
	"[bg]drawtext=x=20:y=560:fontcolor=white:fontsize=30:text='-500ms'[bg]"
	"[bg]drawtext=x=(main_w-text_w)/2:y=560:fontcolor=white:fontsize=30:text='0'[bg]"
	"[bg]drawtext=x=main_w-text_w-20:y=560:fontcolor=white:fontsize=30:text='+500ms'[bg]"
	"[bg][slider]overlay=x=20+((mod(n-1+(${fps}/2)\,${fps})/${fps})*1880)-overlay_w/2:y=500[bg]"

	# Draw frame counter
	"[bg]drawtext=fontcolor=0xffffffdd:fontsize=50:text='%{n}':x=(main_w-text_w)/2:y=main_h-text_h-20"
)

echo -e "\e[32mGenerating ${length}s synchrotest with ${vcodec} at 1920x1080@${fps} FPS\e[0m"

# Execute memory limited video generator
IFS=';'
/usr/bin/ffmpeg \
	-i overlay.png \
	-filter_complex "${filters[*]}" \
	-c:v ${vcodec} \
	-c:a aac \
	-ss 4 \
	-t $((length + 4)) \
	-g ${fps} \
	-y \
	synchro_${fps}_${lowfreq}-${highfreq}_${length}s.mp4