[FFmpeg-user] Thread message queue blocking: when pipe and use filter complex

Jonathan Baecker jonbae77 at gmail.com
Mon Feb 19 09:21:26 EET 2018

Am 19.02.2018 um 02:56 schrieb Carl Eugen Hoyos:
> 2018-02-18 22:56 GMT+01:00 Jonathan Baecker <jonbae77 at gmail.com>:
>> when I use pipe to ffmpeg in combination with *filter_complex
>> overlay, *I always get the message:
>>     Thread message queue blocking; consider raising the
>>     thread_queue_size option (current value: 256)
> What exactly is the problem when FFmpeg shows this message?
Until now I have not seen negative side effects from this message, but 
the documentation says that packages can be discarded - that is way I'm 
a bit worry about it. And as I say, the message comes only when I use 

You think I can safely ignore the message?
> I suspect your command line will always fill the buffer which
> hopefully doesn't matter for you (because it isn't entirely
> clear why you are using the pipe) but does typically matter.
Yes the buffer will always be filled and that is good. In this example 
the pipe makes no sense, right, but normally I loop over a bunch of 
files and pipe them through a buffer to ffmpeg.
>>     ffmpeg -v error -hide_banner -nostats -i "input.mp4" -s 1024x576
>>     -pix_fmt yuv420p -c:v rawvideo -c:a pcm_s16le -f avi - | ffmpeg
>>     -thread_queue_size 256 -i pipe:0 -i "logo.png" -filter_complex
>>     overlay -pix_fmt yuv420p -c:v libx264 -crf 26 -preset ultrafast
>>     -c:a aac -f flv -y /dev/null
> Please understand that reports with "-hide_banner" are useless
> unless you want to report an issue with this option.
Yes you are right, sorry! In a pipe is a bit confusing when both 
processes print information, that is why I hide them, but for debugging 
is necessary.


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