check for negative dts value even if bitstream is already formated, this fixes dts when stream copying.
check for negative dts value even if bitstream is already formated,
this fixes dts when stream copying.


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@16526 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

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