This commit improves returned error codes by forwarding error codes. In
some instances, the hardcoded returned error codes made no sense at all:
The normal error code for failure of av_new_packet() is AVERROR(ENOMEM),
yet there were instances where AVERROR(EIO) was returned.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>