Improve ffmpeg error reporting in case of input/output stream mismatch, enabling a dump_format() of the mismatched output stream. 
Improve ffmpeg error reporting in case of input/output stream mismatch,
enabling a dump_format() of the mismatched output stream. 



git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@13760 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg