[FFmpeg-user] amerge multiple inputs with filter_complex

[Madovsky]

Hi,

I have this command:

ffmpeg -loop 1 -an background.png -i stream11.mp4 -i stream22.mp4 -filter_complex "[1:1][2:1]amerge[audio]; [0:0][1:0]overlay=(main_w-640)/2:(main_h-240)/2[left]; [left][2:0]overlay=((main_w-640)/2)+320:(main_h-240)/2" -map '[audio]' -shortest output.mp4

works well unless "amerge" that prevent the end of the encoding

Buffer queue overflow, dropping.
[Parsed_amerge_0 @ 0x36309c0] Buffer queue overflow, dropping.
    Last message repeated 4 times
frame= 3698 fps= 29 q=28.0 size=    9347kB time=00:02:27.14 bitrate= 520.4kbits/Buffer queue overflow, dropping.
[Parsed_amerge_0 @ 0x36309c0] Buffer queue overflow, dropping.
    Last message repeated 50 times
frame= 3729 fps= 29 q=28.0 size=    9373kB time=00:02:27.14 bitrate= 521.8kbits/Buffer queue overflow, dropping.
[Parsed_amerge_0 @ 0x36309c0] Buffer queue overflow, dropping.
    Last message repeated 54 times
frame= 3761 fps= 30 q=28.0 size=    9375kB time=00:02:28.36 bitrate= 517.7kbits/Buffer queue overflow, dropping.
[Parsed_amerge_0 @ 0x36309c0] Buffer queue overflow, dropping.
    Last message repeated 6 times

and force ffmpeg to continue infinitely
frame= 3798 fps= 30 q=28.0 size=    9375kB time=00:02:29.84 bitrate= 512.5kbits/
frame= 3838 fps= 30 q=28.0 size=    9375kB time=00:02:31.44 bitrate= 507.1kbits/
frame= 3868 fps= 30 q=28.0 size=    9375kB time=00:02:32.64 bitrate= 503.1kbits/

when I remove "amerge" everthing is ok.
I gues the reason to be the background that don't contain any audio chanel so how
to make ffmpeg ignore it ?

Regards

Franck