How to copy keyframe left arm to right armature animation?

The question is pretty much doing the same copying pose:

Pose–Copy Pose; Pose–Paste X-Flipped Pose;

but for all key frame animation.

Performing “Paste X-Flipped Pose” for each keyframe is not an option since it is a mocap generated armature animation with lots of key frames.

hoping there is such feature in blender, thanks

Select the rig half (or just selected bones) that have keyframes, select all the keyframes and copy them

Select the rig half that does not have the keyframes and paste them

On frame 1 give all bones a Loc/Rot keyframe so their animation channels are visible in the graph editor

for some reason it works only for the current frame, not all of them. I though it was because of the bone naming convention whith I had a different one than blender defines but even after I changed it “Arm.L, Arm.R etc” it still behaves the same. thanks though

Works perfectly for me with the above. Try with the rigify rig (enable the addon) to see if it’s your model or your user error

Selecting stuff in the dope sheet is a bit unusual, make sure you got all selected you want to copy and only on the bone you want to copy, or it will try to match bones. Then make sure you have the bones you want to paste to selected in the 3D view. (Using A for all in the dope sheet doesn’t properly select them.)
Mirror with Ctrl+Shift+V.