I played with the idea to do that with H264 streams. This was done with FFmpeg and FFplay. The idea is that you read stream packets from the source and feed it

I played with the idea to do that with H264 streams. This was done with FFmpeg and FFplay. The idea is that you read stream packets from the source and feed it to the decoder, so there is a clear point where you can inject glitching. Because it's difficult to unpack a stream packet, modify it and repack it, I ended hacking the decoder itself. While I had some similar results, I failed to produce something easy to use.