LibavSmashSource and vapoursynth error messages going through stdout

[Mug Funky]

so i'm piping with vspipe and using smashsource to read quicktime files.

so far so good.

but then i come across a quicktime file that, although it loads in vsedit and looks fine, seems to cause an error to be thrown in the terminal i launched vsedit from:
[chan] box returned too many bytes: 20
...something like that.

the problem is this error text goes to stdout - the same place my video is going to be picked up by ffmpeg.

as you could imagine, when ffmpeg receives plain text instead of y4m raw video, it gets rather confused, misdetecting the input as lpc or something, and hanging until i hammer ctrl+c

i can work around this by using ffms2 instead of libavsmashsource, but i think maybe smash only needs a small change to repress error text, or vspipe needs a change to put errors to stderr instead of stdout.