You need to ask yourself what video player or hardware is going to read your videos files. Not all player accept all audio and video codecs, it could fail if one codec is not supported (AAC audio for example) while the video codec is supported. Not all player support all extensions / formats, even though the codec inside is supported (for example Adobe not reading .MKV files that contain H.264 video). Also, even if one codec is supported, your player might not accept some particular sub flavors of it, for example most H.264 players support YUV 4:2:0 chroma subsampling but not always YUV 4:4:4.