"soxr" resampler may hang peculiarly

[milahu]

Summary of the bug:

with a broken input file
with loudnorm filter
with soxr resampling
ffmpeg hangs after transcoding
with the error message "File ended prematurely"
and the transcoding speed slowly drops to zero

ffmpeg version 6.1.2

repro.sh recording:
​https://asciinema.org/a/677569

How to reproduce:

cd $(mktemp -d)

aria2c --seed-time=0 "magnet:?xt=urn:btih:3bbabd438d58e83ae8a9d530dc3520b5c7ee1d80&dn=ffmpeg-hangs-at-File-ended-prematurely&tr=udp%3A%2F%2F89.234.156.205%3A451%2Fannounce&tr=udp%3A%2F%2F208.83.20.20%3A6969%2Fannounce&tr=udp%3A%2F%2F156.234.201.18%3A80%2Fannounce&tr=udp%3A%2F%2F185.243.218.213%3A80%2Fannounce&tr=udp%3A%2F%2F23.140.248.9%3A1337%2Fannounce&tr=udp%3A%2F%2F93.158.213.92%3A1337%2Fannounce"

cd ffmpeg-hangs-at-File-ended-prematurely

chmod +x repro.sh

./repro.sh

repro.sh

#!/bin/sh

i=sie.leben.1988.remastered.german.dl.1080p.bluray.x264-contribution.sample.mkv
af=loudnorm=i=-23.0:lra=7.0:tp=-2.0:linear=true:measured_i=-24.06:measured_lra=10.20:measured_tp=-6.89:measured_thresh=-34.12:offset=2.73

ffmpeg -hide_banner -i $i -map 0:a:0 -af $af -resampler soxr -ar 48k -f wav - > /dev/null

[milahu]

a workaround is to get the actual duration of the audio track
and limit the transcoding process with -to $src_adur

src_path="video.mkv"
src_aid=0 # audio track id

# get the actual duration of the audio track
# https://stackoverflow.com/a/74970367/10440128
src_adur=$(
  ffmpeg -i "$src_path" -c copy -map 0:a:$src_aid -f null - 2>&1 |
  awk -F= 'BEGIN{RS=" "}/^time=/{t=$2}END{print t}'
)

# transcode audio to aac
# limit transcoding to $src_adur
# workaround for: ffmpeg hangs at "File ended prematurely"
af="..."
args="-af $af -resampler soxr -ar 48k"
ffmpeg -i "$src_path" -map "0:a:$src_aid" -to $src_adur $args -f wav - |
  qaac -s --no-delay -o dst.m4a -

[MasterQuestionable]

͏    Can you further ascertain that the audio alone would suffice to reproduce?
͏    And what is the minimal problematic filter? (or maybe happens with random filters..? or even without filter?)

͏    It appears the broken input duration could somehow be more reasonably handled.

[milahu]

a workaround is to get the actual duration of the audio track
and limit the transcoding process with -to $src_adur

this works only in some cases

in other cases
ffmpeg hangs before the actual audio track duration
there is no "File ended prematurely" error message
but also here, the transcoding speed slowly drops to zero

in all cases:

• input samplerate is 48KHz
• loudnorm filter changes samplerate to 192KHz = 4 * 48KHz
• output samplerate is 48KHz
• resampling is done by soxr
• input duration is an odd number of samples

so my guess is that
soxr is waiting for an even number of samples
but the input is exhausted
and ffmpeg does not send "null samples" to soxr
to produce an even number of samples

it works with temporary files
where soxr can see the end of file

---

example: ffmpeg hangs at 99.77%

this is with the audio alone

repro2.sh
​https://asciinema.org/a/678034

tempfiles2.sh
​https://asciinema.org/a/678035

cd $(mktemp -d)

aria2c --seed-time=0 "magnet:?xt=urn:btih:384d43609a14132348dcef567bc4ecaa1da3fe96&dn=ffmpeg-hangs-at-File-ended-prematurely-2&tr=udp%3A%2F%2F23.140.248.9%3A1337%2Fannounce"

cd ffmpeg-hangs-at-File-ended-prematurely-2

chmod +x repro2.sh

./repro2.sh

repro2.sh

#!/bin/sh

# with "-ss 0" ffmpeg hangs at
# size=  246429kB time=00:21:54.28 bitrate=1536.0kbits/s speed=0.0518x
# time: 21:54.28 of 21:57.31 = 1314.28 of 1317.31 = 99.77%
# samples: 1314.28*48000 of 1317.31*48000 = 63085440 of 63230880

# note: in this case, there is no "File ended prematurely" error

set -eu

# eac3, 48000 Hz, stereo, fltp, 224 kb/s
i=American.Dad.S03E05.GERMAN.DL.FS.WEB.720p.h264-TSCC.mkv.a1.mka

o=-
#o=tmp.wav

a=(
  ffmpeg
  -hide_banner
  -nostdin

  -ss 21:54 # hangs at 0.29 -> 21:54 + 0.29 = 21:54.29
#  -to 00:21:57.31
# 21:57.31 - 21:54 = 57.31 - 54 = 3.31
# 3.31 * 48_000 = 158880
# 3.31 * 192_000 = 635520
# 192_000 / 48_000 = 4

#  -ss 0 # hangs at 21:54.28

#  -ss 21:34 # hangs at 20.29 -> 21:34 + 20.29 = 21:54.29
#  -ss 21:35
#  -ss 21:36
#  -ss 21:37 # hangs at 17.28 -> 21:37 + 17.28 = 21:54.28
#  -ss 21:38
#  -ss 21:39 # hangs at 15.28 -> 21:39 + 15.28 = 21:54.28
#  -ss 21:40
#  -ss 21:41 # hangs at 13.29 -> 21:41 + 13.29 = 21:54.29
#  -ss 21:42
#  -ss 21:43 # hangs at 11.29 -> 21:43 + 11.29 = 21:54.29
#  -ss 21:44
#  -ss 21:45 # hangs at 9.29 -> 21:45 + 9.29 = 21:54.29
#  -ss 21:46
#  -ss 21:47 # hangs at 7.29 -> 21:47 + 7.29 = 21:54.29
#  -ss 21:48
#  -ss 21:49
#  -ss 21:50
#  -ss 21:51
#  -ss 21:52 # hangs at 2.28 -> 21:52 + 2.28 = 21:54.28
#  -ss 21:53
#  -ss 21:54 # hangs at 0.29 -> 21:54 + 0.29 = 21:54.29
#  -ss 21:54.1
#  -ss 21:54.2
#  -ss 21:54.21
#  -ss 21:54.22
#  -ss 21:54.23
#  -ss 21:54.24
#  -ss 21:54.25
#  -ss 21:54.26
#  -ss 21:54.27
#  -ss 21:54.28

  # this is needed here to produce an odd number of samples for soxr
  # actual input duration
  -to 00:21:57.31

  -i "$i"

#  -map 0:a:1

  -af loudnorm=i=-23.0:lra=7.0:tp=-2.0:linear=true:measured_i=-23.09:measured_lra=9.10:measured_tp=-9.54:measured_thresh=-33.71:offset=-0.45

  -resampler soxr

  -ar 48000

  -f wav

  "$o"
)

set -x
"${a[@]}" >/dev/null

[milahu]

minimal reproducer

#!/bin/sh
# make ffmpeg hang with "-resampler soxr"
set -eu
i=anullsrc=channel_layout=mono:sample_rate=48000
o=silence.wav
if ! [ -e "$o" ]; then   
  ffmpeg -f lavfi -i "$i" -t 30 -f wav "$o"
fi
i="$o"
o=-
# many other "to" values make ffmpeg hang, but not all
# 3.$RANDOM 4.$RANDOM 5.$RANDOM ...
to=3.1001
a=(
  ffmpeg -hide_banner -nostdin
  -to $to # input "to" breaks
  -i "$i"
#  -to $to # output "to" works
  -af loudnorm=i=-23.0
  -resampler soxr
  -ar 48000
  -f wav
  "$o"
)
"${a[@]}" >/dev/null

by fuzzing, i found some other bad to values
all are greater than 3 seconds

my first 100 to values:

3.0004 3.0007 3.0011 3.0013 3.0016 3.0021 3.0030 3.0033 3.0036 3.1001 3.1002 3.1003 3.1004 3.1005 3.1006 3.1007 3.1008 3.1009 3.1010 3.1011 3.1012 3.1013 3.1014 3.1015 3.1016 3.1017 3.1018 3.1019 3.1020 3.1021 3.1022 3.1023 3.1024 3.1025 3.1026 3.1027 3.1028 3.1029 3.1030 3.1031 3.1032 3.1033 3.1034 3.1035 3.1036 3.1037 3.1038 3.1039 3.1040 3.1041 3.1042 3.1043 3.1044 3.1045 3.1046 3.1047 3.1048 3.1049 3.1050 3.1051 3.1052 3.1053 3.1054 3.1055 3.1056 3.1057 3.1058 3.1059 3.1060 3.1061 3.1062 3.1063 3.1064 3.1065 3.1066 3.1067 3.1068 3.1069 3.1070 3.1071 3.1072 3.2001 3.2002 3.2003 3.2004 3.2005 3.2006 3.2007 3.2008 3.2009 3.2010 3.2011 3.2012 3.2013 3.2014 3.2015 3.2016 3.2017 3.2018 3.2019

all to values smaller than 0.019284 make ffmpeg hang
and when i kill ffmpeg, it says
"Nothing was written into output file, because at least one of its streams received no packets."

some to values make ffmpeg hang at time=00:00:00.00

[MasterQuestionable]

͏    Summary:
͏    ffmpeg -v debug -hide_banner -nostdin -f lavfi -i "anullsrc=mono:48000:d=3.1001,loudnorm,aresample=48000:resampler=soxr" -f null -

͏    ͏"loudnorm" processed output appears to be sort of trigger.

͏    Will this actually be 2 independent problems..?

[MasterQuestionable]

comment:6