JerryBoBerry said:
Keep in mind MKV isn't an actual format you can record to. It's a container that you can put video and audio files of almost any format into.
That's the part I didn't want to go into detail because it gets boring and confusing quickly. MP4 is specially confusing as hell, because people use the name 'mp4' all the time when talking about different things, because the IEC/ISO folks have a history of choosing similar names for things. I've seen it used for:
- (1) Mpeg-4 Part 10 - the video codec more popularly known as H.264
- (2) Mpeg-4 Part 3 - the audio codec known as AAC
- (3) Mpeg-4 Part 14, the actual container format that ends with .mp4, .m4a, .m4v, .m4b and can contain (among others) H.264 and AAC streams.
- (4) both the audio and video streams encoded with H.264 and AAC respectively, as in your reply when you mention 'mp4 inside mkv'.
Now, back to the matter at hand, for simplicity and support I would recommend MP4 (as defined in line 3) is the way to go simply because it's what most cameras, editing software and players support. In fact, when editing/rendering your videos just look for any encoding profiles in your software labeled as 'youtube'-ready/compatible and you are pretty likely to get a good result as those are defined directly by Google as a requirement to use the 'youtube' name in the software and are a good trade-off between size and quality; there's more details in
https://support.google.com/youtube/answer/1722171 if anyone wants to tweak their encoding software.