Like you said, currently only libaom-av1 is available as an AV1 encoder in Shana. Other AV1 encoders like librav1e and libsvtav1 are not included in the ffmpeg library.

Including them amounts to a feature request. Let's see if @Rina is interested in it.

That said, I'm not sure if SVT-AV1(libsvtav1) is more efficient and effective in AV1 encoding than AOMEnc(libaom-av1) in general. Just out of curiosity, can you provide any concrete benchmarking results? 

这都快一年了，还是没有加是SVT-AV1。

根据已有的新闻和其他论坛的讨论，可以认为用SVT-AV1作为AV1的编码器是一大热门选择，其自带的多线程使用、支持最高AVX512指令集与其他功能使用起来十分便捷。

但是根据我目前通过ffmpeg使用libsvtav1的体验，在多线程编码中存在BUG，需要限制lp<=4，在svtav1的gitlab上亦可看到有此类问题的报告(Allocate memory failed when there is over 200GB of free memory (#1893) · Issues · Alliance for Open Media / SVT-AV1 · GitLab)。