[elementalest]

Decoders are notoriously harder to support than encoders due to the various internal formats and encoding/decoding options. Until it supports all the different formats (a lot of effort), it will only be able to play back a few videos.

By focusing on an encoder (at least initially) you can just support a subset of features that work well for you. Then focus on making a decoder that can at least play back videos from your encoder.

More people will find it useful to have an encoder that works all the time, rather than a decoder that only works on a subset of videos.