An example of what Malcolm is writing about.
Intel Haswell (some 10 yrs old):
vainfo: Supported profile and entrypoints
VAProfileMPEG2Simple : VAEntrypointVLD
VAProfileMPEG2Simple : VAEntrypointEncSlice
VAProfileMPEG2Main : VAEntrypointVLD
VAProfileMPEG2Main : VAEntrypointEncSlice
VAProfileH264ConstrainedBaseline: VAEntrypointVLD
VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
VAProfileH264Main : VAEntrypointVLD
VAProfileH264Main : VAEntrypointEncSlice
VAProfileH264High : VAEntrypointVLD
VAProfileH264High : VAEntrypointEncSlice
VAProfileH264MultiviewHigh : VAEntrypointVLD
VAProfileH264MultiviewHigh : VAEntrypointEncSlice
VAProfileH264StereoHigh : VAEntrypointVLD
VAProfileH264StereoHigh : VAEntrypointEncSlice
VAProfileVC1Simple : VAEntrypointVLD
VAProfileVC1Main : VAEntrypointVLD
VAProfileVC1Advanced : VAEntrypointVLD
VAProfileNone : VAEntrypointVideoProc
VAProfileJPEGBaseline : VAEntrypointVLD
VAProfileVP9Profile0 : VAEntrypointVLD
Nvidia GeForce GTX960M
vdpauinfo
...
Decoder capabilities:
name level macbs width height
----------------------------------------------------
MPEG1 0 65536 4080 4080
MPEG2_SIMPLE 3 65536 4080 4080
MPEG2_MAIN 3 65536 4080 4080
H264_BASELINE 51 65536 4096 4096
H264_MAIN 51 65536 4096 4096
H264_HIGH 51 65536 4096 4096
VC1_SIMPLE 1 8190 2048 2048
VC1_MAIN 2 8190 2048 2048
VC1_ADVANCED 4 8190 2048 2048
MPEG4_PART2_SP 3 8192 2048 2048
MPEG4_PART2_ASP 5 8192 2048 2048
DIVX4_QMOBILE 0 8192 2048 2048
DIVX4_MOBILE 0 8192 2048 2048
DIVX4_HOME_THEATER 0 8192 2048 2048
DIVX4_HD_1080P 0 8192 2048 2048
DIVX5_QMOBILE 0 8192 2048 2048
DIVX5_MOBILE 0 8192 2048 2048
DIVX5_HOME_THEATER 0 8192 2048 2048
DIVX5_HD_1080P 0 8192 2048 2048
H264_CONSTRAINED_BASELINE 51 65536 4096 4096
H264_EXTENDED 51 65536 4096 4096
H264_PROGRESSIVE_HIGH 51 65536 4096 4096
H264_CONSTRAINED_HIGH 51 65536 4096 4096
H264_HIGH_444_PREDICTIVE 51 65536 4096 4096
...
and the Packman Mesa adds nothing.
Of course YMMV but with Intel/Nvidia sold in the last 10 yrs it is unlikely that you need the Packman Mesa. You may still need ffmpeg or VLC from Packman, but that is another story.