`Incomplete CU-tree stats file` on 2-pass x265 encode

[aeris]

Summary of the bug:

Unable to 2-pass x265 encode some files.
Crash on the second pass with Incomplete CU-tree stats file

How to reproduce:

./test.sh 2020-08-27.ts
[…]
x265 [error]: Incomplete CU-tree stats file.
Video encoding failed
x265 [info]: frame I:     18, Avg QP:6.68  kb/s: 116260.81
x265 [info]: frame P:   1176, Avg QP:12.74  kb/s: 5613.92 
x265 [info]: frame B:   2443, Avg QP:19.70  kb/s: 327.06  
x265 [info]: Weighted P-Frames: Y:0.0% UV:0.0%
x265 [info]: consecutive B-frames: 29.9% 8.2% 23.4% 4.6% 34.0% 

encoded 3637 frames in 54.02s (67.32 fps), 2610.31 kb/s, Avg QP:17.39
[aac @ 0x55808e19f240] Qavg: 241.662
[aac @ 0x55808e19f240] 2 frames left in the queue on closing
Conversion failed!

[aeris]

Test files to heavy to be enclosed to the ticket, so

Input file:
​https://s3.eu-central-1.wasabisys.com/aeris-assets/ffmpeg-bug/2020-08-27.ts
Output files:
​https://s3.eu-central-1.wasabisys.com/aeris-assets/ffmpeg-bug/2020-08-27
​https://s3.eu-central-1.wasabisys.com/aeris-assets/ffmpeg-bug/2020-08-27-0.log
​https://s3.eu-central-1.wasabisys.com/aeris-assets/ffmpeg-bug/2020-08-27.cutree
​https://s3.eu-central-1.wasabisys.com/aeris-assets/ffmpeg-bug/2020-08-27.mp4

Encoding script:

#!/usr/bin/env bash
INPUT="$1"
OUTPUT="${INPUT%.*}.mp4"
LOG="${OUTPUT%.*}"
VIDEO_PARAMETERS=(-c:v libx265 -b:v 2600k)
AUDIO_PARAMETERS=(-c:a aac -b:a 128k)
CMD=(ffmpeg -y -i "$INPUT" -threads 0 -passlogfile "$LOG" -movflags faststart)

"${CMD[@]}" -pass 1 -x265-params "pass=1:stats=$LOG" "${VIDEO_PARAMETERS[@]}" -an -f mp4 /dev/null
"${CMD[@]}" -pass 2 -x265-params "pass=2:stats=$LOG" "${VIDEO_PARAMETERS[@]}" "${AUDIO_PARAMETERS[@]}" "$OUTPUT"

[Carl Eugen Hoyos]

Please provide backtrace, disassembly and register dump for all crash reports.

[aeris]

Oh sorry, it's not a software crash. Just the encoding stop and exit before the end.