generec rear-seat media player does not play mp4, how to convert to a supported format?

i have recently bought an small monitor/screen with integrated dvd, usb and sd card player. It is one of those generic chinese products with bad documentation.
The device is called: “Digital multimedia Rear-seat entertainment system”,
The manufactor is: Shenzen Suokesi Technology Co., Ltd.
and the model number is: BR1259B

I have problems playing an mp4 file on the device, stored directly on a SD card. The file is visible but when i try to play it i get an error: format or codex not supported. The manual is not very speccific about that, it just says:
USB/SD maximum support 720*576 AVI/DIVX/VOB/FLV/MPG/DAT

the only thing i get from that is, that mp4 is not listed. Do anyone here has an idia to what format i should try to convert my file? And which ffmpeg command to use for that?

Those are old wrapper/codecs. for instance, AVI is a wrapper that usually encapsulates divx video and mp3 audio. After it, we had OGM and MP4, and today wrappers are mostly MKV with a few MP4. Note that these wrapper/codecs can all be run in a modern desktop player like mpv/mplayer. I use SMPlayer as a front end to mpv, which play them all except, possibly, DAT.
This player would be fine five years ago, today it is a kludge (sorry :P).

IMO your best bet is to convert to AVI (XviD + mp3) with avidemux, or perhaps handbrake has a built in profile for this.

IINM AVI won’t support higher resolutions, so you may want to resize larger videos to the LCD resolution (720 x 576 according to the specs you posted).

Also IINM MPG is the video codec found in DVDs, those can be extracted from the DVD and dumped in a pendrive or sd card.

P.S.: I haven’t used ffmpeg for a long time, perhaps someone here can help you.

A simple ‘ffmpeg -i file.mp4 file.mpg’ did not produced playable files. My solution was kind of surprising. Because all of my files where pretty small, i decided to simply burn a DVD with DeVeDe. Interestingly there was a preset for the 720x5xx resolution my device has listed (as written in the first post). After the creation process was finished, i found all of my video files in the movie subdirectory of the output directory of devede, but all of those files where in the mpg format!
At this point i had the hope, that those files maybe are what i needed, and indeed, those files where working on the device. So i do not know how they where converted and in which way this format was different from the format i produced but at least they are working.