For video I maybe suggested to compare of metrics for original (captured) video frames with sent/received video frames, almost all this info is available via WebRTC stats:
original - googFrameHeightInput/googFrameWidthInput/googFrameRateInput
transmitted - googFrameHeightSent/googFrameWidthSent/googFrameRateSent (outbound) & googFrameHeightReceived/googFrameWidthReceived/googFrameRateReceived (inbound)