Question / Help What makes mp4's unreliable?

[keybounce]

This may seem like an odd question, but what makes mp4's unreliable for recording?

Specifically, an mp4 is a streamable format, so (if I understand what streamable means) you should be able to start watching an mp4 file anywhere, find the start of video packet data, find the start of audio packet data, and start showing the images and sounds.

Yet apparently, when OBS records, if it can't write something at the end of the file, the entire mp4 file is worthless.

So what am I not understanding here? This doesn't make sense to me, but since this fits reality, I must be misunderstanding something, right?

 

[Narcogen]

If anything interrupts the recording into an mp4 container, you will likely lose the entire recording.

So if OBS crashes, or your OS crashes, or you lose power, or you inadvertently fill a drive because you record too long or the file is too large... you will probably lose everything.

If you record in an .flv or better yet an .mkv, this will not happen-- the partial file will be completely usable.

 

[keybounce]

I understand that you do lose the recording when you use an mp4.

I'm trying to understand *why*.

What makes the mp4 container both streamable (so I can start listening at any point in the file, and figure out what I'm listening to), and yet fragile.

 

[Harold]

The critical components of an mp4 (codec information, etc) are written to the file LAST and not first.

 

[keybounce]

That's ...

But ...

WHY?!?

Also: How can you stream them then?

 

[Harold]

OBS' stream output is FLV over RTMP.

As for streaming from websites, the players cheat and usually aren't running from corrupted files anwyay.