At 04:24 PM 7/24/2017 -0400, you wrote:
I want to preserve formatting for audio and video and apply
normalization to the audio - in batch. Surely there must be a way to script
this.
Here's the code that I use for both boosting and companding. If $Compressor
is 1, it makes up parameters for mencoder. If $Compressor is not 1, it
makes up parameters for ffmpeg.
#
# If the user wants the input volume boosted by a fixed amount, just set
# the boost volume to that amount.
#
if [ ${FixedBoost} -ne 0 ]; then
BoostVol=${FixedBoost}
#
# Otherwise, if the user wants the input volume boosted so that the peak is
# near 0dB, we need to figure out how much boost is necessary.
#
else
#
# Note that we must use ffmpeg to detect the volume of the input file
# because ffprobe doesn't offer this feature. So, even if the
# compressor being used is mencoder, ffmpeg is still required to use
# this feature. Also, we look at the first 300 seconds (five minutes)
# of the input file to get an accurate picture of the maximum volume.
# This takes about 20-30 seconds but gives a much better idea of what
# the maximum volume really is.
#
# Once we have a boost volume amount, we can apply it with the volume
# filter
#
if [[ ${AudioBoost} -ne 0 && -x ${CompressFFMpeg} ]]; then
BoostVol=`${CompressFFMpeg} -i $2 -af "volumedetect" -to 300
-nostats -f null -y /dev/null 2>&1 | grep -e '^\\[Parsed.*max_volume' | sed
's/^.*max_volume:\\s-\\([0-9\\.]*\\).*$/\\1/g'`
BoostTrue=`echo "${BoostVol} > 1" | bc`
if [ ${BoostTrue} -ne 0 ]; then
BoostVol=`echo "scale=1; ${BoostVol} - 1" | bc`
else
BoostVol=0
fi
else
BoostVol=0
fi
fi
.
.
.
#
# If we are boosting the audio, set the audio filter to boost it by the
# amount that we pre-calculated. Note that this has no effect on dynamic
# range, it just makes everything louder.
#
BoostTrue=`echo "${BoostVol} > 0" | bc`
if [ $BoostTrue -ne 0 ]; then
if [ $Compressor == 1 ]; then
AudioFilter="-af volume=+${BoostVol}dB"
else
AudioFilter="-af volume=${BoostVol}dB"
fi
fi
#
# If we are normalizing the audio, set the audio filter to lessen the
# dynamic range.
#
# For mencoder, the volume normalization filter seems to work well (having
# tried it on quite a bit of recorded TV, which has much too high dynamic
# range in many cases).
#
# For ffmpeg, the compand filter with the parameters shown seems to work
# well also. Here's the note from tugshank at forum.videohelp.com:
#
# -af "aformat=channel_layouts=stereo,
#compand=0 0:1 1:-90/-900 -70/-70 -30/-9 0/-3:6:0:0:0"
#
# channel_layouts=stereo forces mono to stereo, just in case
#
# compander (compressor/expander):
#
# attack - 0
# release - 1
# -90 dB in, infinity out
# -70 dB in, -70 dB out
# -30 dB in, -9 dB out
# 0 dB in, -3 dB out,
# soft knee 6
# 0 dB makeup gain
# input level 0 dB
# lookahead 0.
#
# Specifically made for 'whisper+explosion' scenes.
#
# For publishing video, EBU R128 is currently the preferred standard. To
# use EBU R128, one must build ffmpeg with libebur128. Normally, this
# isn't the default so you must use "--enable-libebur128" when you run
# configure. Then, the "loudnorm" audio filter can be used, as in
# "-af loudnorm". To figure out if loudnorm is available, use the
# following:
#
# ffmpeg -filters 2>/dev/null | grep loudnorm
#
if [ ${AudioNorm} -ne 0 ]; then
if [ $Compressor == 1 ]; then
AudioFilter="-af volnorm=2:0.75"
else
AudioFilter="-af \"aformat=channel_layouts=stereo,compand=0 0:1
1:-90/-900 -70/-70 -30/-9 0/-3:6:0:0:0\""
fi
fi
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