Script for scaling down HD movie after recording using TVheadend to a DVBcut compatible SD movie for archiving

scaledown-HD-video-to-DVBcut-compatible-SD-mpeg.sh

#!/bin/sh

set -x -e

q=3.5
# q3.4 = 324354 bytes/s
# q3.5 = 251931 bytes/s -> best choice

infile="$1"              # testrec-hd.ts
outfile="${1%.ts}.mpeg"  # testrec-sd-q$q.mpeg"
outfiletmp="${1%.ts}.~part~.mpeg"  # testrec-sd-q$q.part.mpeg"

panic() {
  echo "$0: $1" >&2
  exit 1
}

[ -f "$infile" ]    || panic "infile $infile does not exist"
[ ! -f "$outfile" ] || panic "outfile $outfile already exists"

tmpfile=/tmp/$$.tmp

rm -fv "$outfiletmp" "$tmpfile"

ffmpeg -i "$infile" >$tmpfile 2>&1 || true

cat "$tmpfile"

grep -q "Video: h264" "$tmpfile" || panic "Unexpected format of $infile"
grep -q "Input #0, mpegts, " "$tmpfile" || panic "Unexpected format of $infile"

case "$(cat "$tmpfile" | grep ': Video: ' | grep -Po ' [0-9]+x[0-9]+ ')" in
  ' 1280x720 ') dims=720x576;;   # factor 1:0.5625
  *)
    panic "Unable to detect source dimensions"
esac

if ffmpeg -i "$infile" -map 0:v -map 0:a:0 -map 0:a:1 -f mpegts -s "$dims" -r 25 -vcodec mpeg2video -qscale:v $q -acodec copy "$outfiletmp"; then
  touch --reference "$infile" "$outfiletmp"
  mv -v "$outfiletmp" "$outfile"
  echo "ok."
else
  r=$?
  rm -fv "$outfiletmp"
  exit $r
fi

# HD Reference file
#
# Input #0, mpegts, from 'testrec-hd.ts':
#   Duration: 00:10:30.42, start: 44092.375256, bitrate: 11724 kb/s
#   Program 9038
#     Stream #0:0[0x50]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 100 tbc
#     Stream #0:1[0x51](ger): Audio: mp2 ([4][0][0][0] / 0x0004), 48000 Hz, stereo, s16p, 192 kb/s
#     Stream #0:2[0x52](eng): Audio: mp2 ([4][0][0][0] / 0x0004), 48000 Hz, stereo, s16p, 192 kb/s
#     Stream #0:3[0x5b](ger): Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, 5.1(side), fltp, 448 kb/s
#   No Program
#     Stream #0:4[0x6e]: Audio: mp3, 0 channels, s16p
# At least one output file must be specified


# HD downscaled q=3.5
#
# Input #0, mpegts, from 'out-sd-q3.5.mpeg':
#   Duration: 00:10:30.48, start: 1.400000, bitrate: 2015 kb/s
#   Program 1
#     Stream #0:0[0x100]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv), 720x576 [SAR 64:45 DAR 16:9], max. 104857 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
#     Stream #0:1[0x101](ger): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16p, 192 kb/s
#     Stream #0:2[0x102](eng): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16p, 192 kb/s
# At least one output file must be specified


# SD Reference file
#
# Input #0, mpegts, from 'testrec-sd.mpeg':
#   Duration: 00:10:30.06, start: 45811.850811, bitrate: 2390 kb/s
#   Program 1
#     Stream #0:0[0xa0]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv), 720x576 [SAR 64:45 DAR 16:9], max. 6000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
#     Stream #0:1[0x50](ger): Audio: mp2 ([4][0][0][0] / 0x0004), 48000 Hz, stereo, s16p, 128 kb/s
#     Stream #0:2[0x51](eng): Audio: mp2 ([4][0][0][0] / 0x0004), 48000 Hz, mono, s16p, 64 kb/s
#   No Program
#     Stream #0:3[0x20]: Audio: mp3, 0 channels, s16p
# At least one output file must be specified

# name				size	time		s	b		b/s		fazit
# testrec-hd-reference.ts	hd	00:10:30.42	630.42	923901184	1465532.79
# testrec-sd-reference.mpeg	sd	00:10:30.06	630.06	188298356	298857.82
# testrec-sd-q1.mpeg		sd	00:10:30.42	630.42	347443364	551129.98
# testrec-sd-q2.mpeg		sd	00:10:30.42	630.42	346557696	549725.10
# testrec-sd-q2.4.mpeg		sd	00:10:30.42	630.42	343700284	545192.54
# testrec-sd-q3.mpeg		sd	00:10:30.42	630.42	204833332	324915.66	ok
# testrec-sd-q3.1.mpeg		sd	00:10:30.42	630.42	204833332	324915.66
# testrec-sd-q3.2.mpeg		sd	00:10:30.42	630.42	204833332	324915.66
# testrec-sd-q3.3.mpeg		sd	00:10:30.42	630.42	204479328	324354.13
# testrec-sd-q3.4.mpeg		sd	00:10:30.42	630.42	204479328	324354.13
# testrec-sd-q3.5.mpeg		sd	00:10:30.42	630.42	158822588	251931.39	best with small size
# testrec-sd-q3.6.mpeg		sd	00:10:30.42	630.42	158822588	251931.39
# testrec-sd-q3.7.mpeg		sd	00:10:30.42	630.42	158809240	251910.22
# testrec-sd-q3.8.mpeg		sd	00:10:30.42	630.42	159331504	252738.66
# testrec-sd-q4.mpeg		sd	00:10:30.42	630.42	159331504	252738.66	usable
# testrec-sd-q5.mpeg		sd	00:10:30.42	630.42	132361400	209957.49	bad
# testrec-sd-q6.mpeg		sd	00:10:30.42	630.42	116979992	185558.82
# testrec-sd-q7.mpeg		sd	00:10:30.42	630.42	106930640	169618.10
# testrec-sd-q8.mpeg		sd	00:10:30.42	630.42	99986860	158603.57
# testrec-sd-q9.mpeg		sd	00:10:30.42	630.42	94175216	149384.88
# testrec-sd-q10.mpeg		sd	00:10:30.42	630.42	89957248	142694.15
# testrec-sd-q11.mpeg		sd	00:10:30.42	630.42	86698832	137525.51