[FFmpeg-user] split/select/overlay Buffer queue overflow, dropping

[Basin Ilya]

Hi list.
Copying from
http://stackoverflow.com/questions/32060554/split-select-overlay-buffer-queue-overflow-dropping

This command is a simplified version of the real command. It's supposed
to write 4 seconds of first input into out0.mkv and overlay the same
first input on top of second input and write the result into out1.mkv

    ffmpeg -y \
        -f lavfi -i testsrc=s=640x480:d=10:r=25 \
        -f lavfi -i testsrc=s=640x480:d=10:r=25 \
        -filter_complex "
            [0:v]split=2[in0-0][in0-1];
            [in0-0]select='lt(t,4)'[out0];
            [1:v][in0-1]overlay[out1]
            " \
        -map '[out0]' out0.mkv \
        -map '[out1]' out1.mkv

During processing it prints Buffer queue overflow and in the end there's
a still image in out1.mkv.

My guess is that one of the nodes in filter graph cannot consume new
frames from one input, because it's waiting for another input, but I
don't understand why.

It looks like out1 is waiting for out0, although they should be independent.

Why do I use "split"? Because the real source is /dev/video0.