Of my more than 900 xvid movies 30% are packed bitstream and are not played back, but 20% are just xvid and are not supported either. I am sure all of them worked on my older Z9S. Rather than trying to improve the HT features (fanart etc.) one should concentrate on the basic player function as long as they dont work properly.
You can unpack them with MPEG4Modifier https://www.videohelp.com/software/MPEG4-Modifier . I had to do this with quite a few of my early files. Several I had to run through avidemux and re encode. No noticeable degradation.
Xvid is very old tech for low quality DVD rips and not an area you are likely to get concentration from developers for a current 4K player. You should find ZDMC plays them all just fine (as it will use the software Kodi player instead of the default Zidoo hardware player). You may find simply converting the container to mkv will be enough but that can depend on the original codec used. You may also find a lot of old movies that were originally released on VHS and DVD are now available on 1080p or even 4K
Since there is no mention of supported codecs in the spec: "Rumor has it that support for h264 will also be abandoned in the near future since HEVC is the future!"
I wouldn't listen to the rumour mill. There are too many files around, H264 is presently well represented but the time will come of course. XVID is just a superseded technology by decades. Providing support for every bygone codec of course will come at a cost to newer material to fit the available space. There are always tradeoffs I've converted all my remaining XVID's and DivX's to H264 and AC3 audio, others, the most, I've replaced with DVD's of in a few cases Blu ray versions. Using AVidemux is simple and fairly quick as is Vidcoder and similar. For me a project for a wet Saturday afternoon
MPEG2 was developed in the 80s and that's still very much supported. Codecs tend to have a unique life span of 20 years or so and with AVC/H.264 developed in the early 2000s and HEVC/H.265 coming along 20 years ish later that kind of makes sense. But that's unique lifespan, and because of its ubiquity I think AVC will be with us for decades to come.
After reencoding all my 1452 xvid movies ( to avoid future problems due to the lack of competence to continue support for established codecs - as far as I can tell it is the only brand to discontinue XVID) I only hope Zidoo will not stop mp3 and AC support for the soundtracks!
If anything isn't playing in Home Theater, just use ZDMC. I do this for: - xvids avi files. divx is also hit or miss - 720p 10 bit x264 encodes which was popular for anime These types of files I just play in ZDMC.
Since I do not use HT at all, because of all the drawbacks and errors, I use ZDMC with the external player, which would mean that I have to change players every time I encounter the "XVID" problem.
I'm pretty familiar with my library so I know exactly which files are AVI files. So if I want to play those, I just open ZDMC. Anything else, I use HT4.0.