Certain files won't play - suspected codec issue
Forum rules
Please make sure you follow the Problem Reporting Guidelines before posting if you want a reply
Please make sure you follow the Problem Reporting Guidelines before posting if you want a reply
Re: Certain files won't play - suspected codec issue
VLC isn't really used in UMS, I think it was more in use many moons ago and that it still exists for that reason. Unless you change your configuration from the default, VLC won't be used though. FFmpeg is the primary transcoding engine these days, and MEncoder is used as a fallback for some cases that FFmpeg doesn't handle.
This is more complicated that you seem to think though, I doubt the problem is that FFmpeg can't handle the transcoding. For every renderer (e.g a TV), a configuration file exists that tells UMS what formats/codecs are supported. This is used to determine when transcoding is needed. If the renderer configuration file in use doesn't match the actual capabilities of your TV, certain formats/codecs will fail to play. You must edit the renderer configuration file to make this work. There is no straight forward manual for how to do this, and I personally don't find it that intuitive either, but you can find lots of information about it scattered around this forum.
This is more complicated that you seem to think though, I doubt the problem is that FFmpeg can't handle the transcoding. For every renderer (e.g a TV), a configuration file exists that tells UMS what formats/codecs are supported. This is used to determine when transcoding is needed. If the renderer configuration file in use doesn't match the actual capabilities of your TV, certain formats/codecs will fail to play. You must edit the renderer configuration file to make this work. There is no straight forward manual for how to do this, and I personally don't find it that intuitive either, but you can find lots of information about it scattered around this forum.
Re: Certain files won't play - suspected codec issue
I think many have started to drop DivX support. The problem is that DivX is licensed, so the manufacturer must pay license fees to whoever cashes in on this when they make devices which support it. As such, this extra cost must be compared to the value it has for customers, and since DivX is now quite old and has since been replaced by superior codecs, I can understand if they don't think it's worth it.
That said, DivX is only really MPEG-4 Video, so there are other alternatives (like XVid or "pure" MP4v) that could be used with the same quality and without the licensing fee. Also, AVC, HEVC, VP8, VP9, AV1 and others are superior in quality/compression. I don't think there is a good reason to encoding anything using DivX in 2020, but it is still useful to be able to play older material that is DivX encoded, which is where transcoding is key.
That said, DivX is only really MPEG-4 Video, so there are other alternatives (like XVid or "pure" MP4v) that could be used with the same quality and without the licensing fee. Also, AVC, HEVC, VP8, VP9, AV1 and others are superior in quality/compression. I don't think there is a good reason to encoding anything using DivX in 2020, but it is still useful to be able to play older material that is DivX encoded, which is where transcoding is key.