What is the difference between avi and mp4 file endings?

[Peter1234]

I am new to mp4 encoding so please forgive a stupid question. I have been using TMPGEnc to encode using the x264VFW codec for video and mp3 codec for audio. This produces a file with an avi ending. But, I can change the ending from avi to mp4 and the file still plays in all the players. The avi and mp4 endings seem to be interchangeable. Is there a difference? Where would I look to find out more?

[IRMA1024]

to whatever you change the ending it is still playable, depending on player, usually the player check the container data not the file ending, avi and mp4 is both container, different container offcourse, see the FAQ for both container

[Peter1234]

IRMA1024:
Thanks.

[leowai]

To be more specific, I prefer to say it's the "file extension" rather than "file endings". The words "file endings" confuse me as it appears like the modification of binary values at the end of the file.

File extension is used in OS for document classification. It guides your OS to open the files with that particular file with certain (associated) program. However, just like IRMA1024 mentioned, the video will be still playable if the program is smart enough to detect the content of the file rather than only depends on the file extension.

[Peter1234]

leowai:
Thanks. I will try to remember that.

[MeteorRain]

like in MPC, if avi and mp4 are both open in directshow mode, you can switch between them freely. but, change a file extension should be avoided, as it'll confuse ppl who play it.
avi should have a avi extension. so do others.

[bond]

changing extensions is absolute nonsense. i repeat: absolute nonsense

.avi and .mp4 are NOT the same containers and you can not change the extensions

the reason why YOU (this doesnt mean everyone can do it) could do it, is because you propably have the haali parser installed, which handles both .avi and .mp4

of course in other players, eg quicktime, or with other parser you cant do that

moved, as this is not an avc issue