The Xiaomi Mi Note Pro and Mi Note Review

Video Performance

Now that we’ve discussed still image performance, we can start to look at video performance. This is often a difficult area for a smartphone due to the extra constraints and the real-time nature of this type of workload. While it might be possible to defer saving a video until recording has finished or do so in an asynchronous manner, image processing is on a strict deadline to finish in 32ms or less if there are to be no frame drops in a video. It’s also important to maximize quality here by using advanced image processing techniques such as electronic image stabilization to eliminate hand shake and possibly HDR to improve dynamic range within the video. In the case of the Mi Note line, as far as I can tell Xiaomi is solely relying upon the SoC’s ISP for video processing so pretty much any difference between the Mi Note Pro and Mi Note would come down to Xiaomi’s tweaks and the difference in SoC ISP/ISP software stack.

In the case of 1080p30 video, the Mi Note and Mi Note Pro uses 15 Mbps H.264 baseline to encode the video, which is odd because the encoder blocks are definitely capable of H.264 high profile. The audio stream is 96 Kbps AAC, which should be sufficient for acceptable audio quality. It’s really strange that this is the case, but for whatever reason it looks like the Mi Note Pro basically doesn’t stabilize the video footage at all while the iPhone 6 has strong video stabilization and almost looks like it’s using OIS without the associated issues with mid-video OIS resets. The Mi Note is stabilized to some extent but it clearly suffers from the classic problem of OIS-stabilized video in the form of moments of stability punctuated by sharp, jerky camera movements. Compared to the iPhone 6 there are also problems with a bit of excessive blur as once again at the end of the video you can see how distant, detailed objects have fine detail blurred away. Video output here isn’t too far off from the Galaxy S6, but the OIS of the Galaxy S6 is definitely more effective and also has more detail.

Interestingly enough, neither phone supports 1080p60 video despite the presence of 4K30 support, which means 1080p60 video definitely has to be possible.

Moving on to 4K video comparisons, since the iPhone doesn’t support 4K video I used the Galaxy S6 as a comparison point. Weirdly enough it looks like 4K video actually has OIS working due to the characteristic reset behavior that we’ve seen in a number of videos recorded with OIS on. Both the Mi Note and Mi Note Pro have the same audio settings and encoder settings here. The only difference from 1080p30 is that the Mi Note Pro uses 42 Mbps encoding, while the Mi Note uses 40 Mbps encoding for video. Weirdly enough, in this case I actually think the Mi Note Pro ends up with better image quality than the Galaxy S6 as the video is sharper and generally has better detail with more realistic colors. However, the Mi Note Pro’s stabilization is clearly worse and Xiaomi needs to improve their image stabilization if they want to really beat the very best here. The Mi Note is clearly not as good as the Mi Note Pro as the colors are like the Galaxy S6’s, with less detail and dynamic range than the Mi Note Pro almost universally.

In slow motion, the Mi Note Pro and Mi Note both lack any sound recording and both roughly have 8 Mbps H.264 baseline encoding. However, it’s interesting to see that the Mi Note Pro has this encoding for 720p30 playback, while the Mi Note only has about 26 FPS. Both have roughly equivalent detail in these videos, but the Mi Note Pro has more natural processing while the Mi Note has a higher contrast setting with some odd color shifting. Compared to the iPhone 6, slow motion footage is zoomed in closer but for some reason it doesn’t feel like detail actually improves much. Interestingly, the Galaxy S6 is clearly superior at slow motion video than everything else in these comparisons, which is probably mostly attributable to the widest field of view out of all four phones in this test.

Overall, the video performance of the Mi Note and Mi Note Pro is a mixed bag but mostly good. The Mi Note clearly suffers from tuning issues that the Mi Note Pro avoids, but for whatever reason 1080p30 video on the Mi Note Pro clearly has no stabilization at all. If Xiaomi improves video stabilization, they actually wouldn’t be too far off from the iPhone 6 in video quality after some improvements to fine detail processing. The Galaxy S6 still clearly stands out here for better OIS than the Mi Note, but this is mostly of interest in low light shots rather than video as I’m increasingly convinced good EIS is much better for video than OIS. It’s interesting to also see how in 4K the Mi Note Pro is clearly better than the Galaxy S6 for detail, even if stabilization means it’s really hard to see the detail if the person behind the camera is unable to keep the phone still. The Mi Note Pro is also consistently better at accurately capturing the color and white balance of this outdoor scene, which is surprising given that the Galaxy S6 has a color spectrum sensor to help determine white balance.