man avconv > bla.txt
<standard input>:1716: warning [p 19, 7.2i, div `an-div', 0.2i]: can't break line
<standard input>:1719: warning [p 19, 7.5i, div `an-div', 0.2i]: can't break line
<standard input>:3608: warning [p 38, 13.7i]: can't break line
<standard input>:3750: warning [p 40, 7.3i]: can't break line
<standard input>:4468: warning [p 48, 0.5i]: can't break line
<standard input>:5246: warning [p 55, 12.3i]: can't break line
<standard input>:5354: warning [p 56, 12.2i]: can't break line