This reverts commit e0c6b32046.
Said commit changed the behavior of the demuxer and decoder in a non
backwards compatible way.
Demuxers should make extradata available at init if possible, and send
new extradata as side data within a packet if needed.
A better fix for the remuxing crash will follow.
Signed-off-by: James Almer <jamrial@gmail.com>
Also test the fallback to png creation for a single frame.
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
