[HELP] Hybrid introducing audio delay that is not present in source material

[4i4oVi40]

I looked at the DebugOut file and then did some more testing.

Now it seems to me that the "Compensate aac encoder delay" option does nothing when creating a mp4 file with MP4Box. Whether or not it's checked, Hybrid produces exactly the same mp4 file.

I took the CLI options and tried to recreate the process outside of Hybrid like that:

ffmpeg -i foo.avi -map 0:1 -vn -sn -ac 2 -ar 48000 -acodec pcm_s16le -f wav -map_metadata -1 - | fdkaac --bitrate-mode 4 --profile 2 --transport-format 0 --gapless-mode 2 --ignorelength -o foo.aac -

ffmpeg -noautorotate -nostdin -i foo.avi -map 0:0 -an -sn -vf zscale=rangein=tv:range=tv -pix_fmt yuv420p10le -strict -1 -vsync 0 -f yuv4mpegpipe - | x265 --output-depth 10 --y4m --profile main10 --limit-modes --no-early-skip --no-open-gop --opt-ref-list-length-pps --lookahead-slices 0 --crf 28.00 --opt-qp-pps --cbqpoffs -2 --crqpoffs -2 --limit-refs 0 --ssim-rd --psy-rd 2.50 --rdoq-level 2 --psy-rdoq 10.00 --aq-mode 0 --deblock=-1:-1 --limit-sao --no-repeat-headers --range limited --colormatrix bt709 --output foo.265 -

Then I muxed with MP4Box, with and without delay.

MP4Box -add foo.265:name="" -brand hvc1 -add foo.aac -mpeg4 -new foo.mp4

MP4Box -add foo.265#video:fps=24:delay=41:name="" -brand hvc1 -add foo.aac -mpeg4 -new foo_.mp4

Again, the resulting mp4 files are exactly the same.

Also, mkvmerge produces mkv with synced video and audio only when "Compensate aac encoder delay" is not checked.  So I start to think that keeping "Compensate aac encoder delay" unchecked for both mp4 and mkv is actually preferable.