# ./thirdparty/ffmpeg-6.1/ffmpeg -encoders | grep av1
 V....D libaom-av1          libaom AV1 (codec av1)
 A....D wmav1               Windows Media Audio 1

Hm, I wonder why so few av1 encoders are enabled?

Because  additional ones tend to have external dependencies we normally do not carry? Also, at least on aarch64 librav1e was a bit of disappointment, at least on default  settings it was SLOW.

In addition to what Andrew reported, when building FFmpeg, you have to specifically enable libsvtav1 which has not been done, but could be if someone tests that and finds it useful.

But what is actually more interesting is that there is still no vaapi_av1 which is what Andrea was trying to get working (just to find out that his hardware would not support anyway).  There may be some other trick to that too since it certainly seems to exist as a codec in this file:  ./cinelerra-5.1/thirdparty/ffmpeg-6.1/libavcodec/allcodecs.c

In comparison I get this list from Packman's ffmpeg 6.0.1 on Tumbleweed-Slowroll:

fmpeg -encoders -hide_banner | grep av1
 V....D libaom-av1           libaom AV1 (codec av1)
 V....D librav1e             librav1e AV1 (codec av1)
 V..... libsvtav1            SVT-AV1(Scalable Video Technology for AV1) encoder (codec av1)
 V....D av1_nvenc            NVIDIA NVENC av1 encoder (codec av1)
 V....D av1_amf              AMD AMF AV1 encoder (codec av1)
 A....D wmav1                Windows Media Audio 1

ffmpeg -hwaccels -hide_banner
Hardware acceleration methods:
vdpau
cuda
vaapi
qsv
drm
vulkan