Made some tests on 700D:
-Activating RAW stream in mv1080 (without RAW recording) while recording H.264 makes LiveView choppy and this affect the recorded H.264 video, changing EDMAC channels doesn't help (same result, beside H.264 recording doesn't use EDMAC channels which we are using, the problem isn't with EDMAC channels because continue reading)
-Recording H.264 proxy with uncompressed RAW video in mv1080, H.264 video would be choppy with some pink frames in the beginning and in the end, RAW video have 50% corrupted frames, 50% frames looks fine (something like that), lowering RAW video resolution might help a bit but not much, in lossless compression RAW data is completely corrupted and recording stops after ~4 seconds
-Well, in mv720, FPS override to 25 FPS, H.264 proxy works just fine with uncompressed RAW, LiveView is smooth, H.264 video is just fine (doesn't have choppiness or pink frames in the beginning or in the end), RAW video also fine, no corrupted frames, but with lossless compression same result (RAW video is completely corrupted, recording stops after ~4 seconds), this explains that EDMAC channels aren't the problem
-Canon H.264 buffer alert comes after some seconds after starting recording RAW video with H.264 proxy (mv720 @ 25 FPS), the recording stops after ~14 seconds, lowering RAW resolution or FPS don't affect the ~14 seconds recording time, also we didn't reach SD card write speed limit (so the write speed isn't the problem here)
-In mv1080 1736x1158 * 24 FPS RAW data being processed in LiveView vs mv720 1736x696 @ 25 FPS RAW data being processed (more memory + memory bandwidth being used in mv1080)
-So it's probably memory allocation problem, the area of RAW data stream in memory which affects H.264 stream, or it might be just memory speed isn't fast enough for RAW data and H.264 proxy in mv1080 (well, I don't think it's a really memory bandwidth problem, continue reading)
-Using FPS override in mv1080 @ 4 FPS then recording RAW data with H.264 proxy have same problems as in mv1080 @ 24 FPS --> it's clearly not the memory bandwidth
-I don't know how to change allocation area yet