Relevant bit

The DMCA filing states that several files in the Rockchip MPP repository are derived from FFmpeg’s libavcodec sources. It lists AV1, H.265, and VP9 decoder files, and claims the copied code is clear because of matching structure, comments, and commented-out calls to FFmpeg functions with their original names.

Much of FFmpeg, including libavcodec, uses the GNU Lesser General Public License version 2.1. This license allows reuse, but only if certain rules are followed. These rules include keeping copyright notices, giving proper credit, and ensuring any shared code remains under an LGPL-compatible license.

The DMCA notice says Rockchip broke these rules by removing the original copyright and author details, claiming the copied code as their own, and sharing it under the Apache license, which does not meet LGPL requirements here.

They're Chinese, they ain't bothering to read and change the License (especially if they don't have many english-speaking devs)

Cut and paste source code into your repo, which you can do, then offer the whole thing under apache which you cannot do.

I didn't look into how the code is used, but LGPL can still easily get an entire project.