"Some state support for MPEG4. ls that the same as MP4?"
No be careful there, the two (
MP4 the container specification and
MPEG4-AVC the video compression standard) are not necessarily equal/interchangeable.
MP4 is
a container (think of it as a folder) which can (and often does) contain a
H.264/MPG-4-AVC video stream (likely encoded using
x264) along with a separately encoded audio stream (most likely
AAC). But
importantly it
can also contain audio and video encoded with other formats/codecs.
So even if you player can handle a MP4
container it won't necessarily be able to decode the audio/video streams found inside it. So you need to check that your player supports not only the container (like MP4 or
MKV) but also the audio (
AAC,
AC-3,
DTS etc.) & video (
H.264,
H.265,
H.262) codecs used to encode the content inside that container.
Personally I prefer using MKV as a container as it allows multi-channel audio formats like DTS and AC3 to be passed though to your AVR untouched, as well as support for chapter markers. It also allows 'soft subtitles' to be included which can then be toggled on and off in your player, rather than having to be burnt into the video. If you're ripping your own DVD/BluRay's
MakeMKV is perfect for this task. If you want to further
reduce down the size of the video track you can run the resulting MKV file though
Handbrake. H.264 (x264) with the frame rate set to 'same as source' is probably a safe starting point. I'd leave the audio tracks alone (set to 'passthru' under the audio tab) if your player (or TV/AVR) can handle them without conversion as the reduction in file size there will be minimal.
Remember MKV and MP4 are
containers, it's
what is in the container that a player will likely have the issue with, not the container format itself.
(* the major exception here is Apple's official apps which don't support MKV as a container)
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The issue with DVD players (at least cheap DVD players) is that it's an old technology and so even the players that 'support MP4' (
see above for why this isn't clear cut) are likely to have very basic interfaces for browsing/playback and will likely be running a firmware that hasn't been updated in ages — and so may have issue with any encodings that deviate slightly from the norm.
If you have a spare HDMI port you may be better off getting a
cheap device that can run
Kodi.
Not only will Kodi play back (almost) any file format you throw at it, but it will also scrape metadata and index your movies into a
nice interface. It's also free / open source and gets regular updates. You can try out the
Mac/PC version of Kodi to get a feel for how it works.
If money isn't the limiting factor then a
Vero 4K+ (designed solely to run OSMC's install of Kodi) would be my recommendation for an easy life, as it will just work out-of-the-box without issues.
But if you just want something super low-cost to simply play back the occasional file then there is a whole world of cheap 'Kodi boxes' on eBay/Amazon, but you'll need to
do some homework to find out which of those are issue free for your use cases. The cheapest boxes (<£30) are likely struggle with 4K content and advanced audio codecs, but for basic MP4/MKV (1080p / H.264) playback they should be fine.
You can also
side-load Kodi on to an Amazon Fire (which is likely a better & more stable option than a no-name 'Kodi Android Box' off eBay) or install
Kodi/OSMC yourself on a small/cheap
SBC like a
Raspberry Pi. But both of those will require some additional work/steps in terms of initial setup.