[FFmpeg-user] Concat and extract image cause FFmpeg to hang in 3.3 and 3.4

[Jeff Wang]

Hi everyone,


In our product, we have a command that concatenate two FLAC audio input files at the same time extract the album art from the second input. The command works fine in FFmpeg 3.1 and 3.2; however, it gets stuck (the process never finishes) in 3.3 and 3.4. There is also no error message. The command follows:


ffmpeg -i topia.flac -i topia_png.flac -threads 0 -map_chapters -1 -f flac -filter_complex "[0:a:0][1:a:0]concat=n=2:v=0:a=1[cat_a]" -map "[cat_a]" -acodec flac -sample_fmt s16 -ac 2 -ar 44100 -sn -vn topia.flac+topia_png.flac.flac -map 1:1 -f image2 -vcodec copy -frames:v 1 extract.png


We're in the process of upgrading to 3.3 and this is prevent us from doing that. Any advice is appreciated.


Jeff