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

[Jonathan Baecker]

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 
filter_complex.

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.

Jonathan