I think some of you may not know this but the motion jpeg codec is actually highly desirable for many videographers.
Why? The all-i nature of the codec. Video compression works by creating a series of i-frames from which subsequent frames have their deltas encoded from (and occasionally b-frames which are like i-frames but they apply to previous frames). These frames are added at either a fixed or variable rate. The more i-frames and b-frames the higher the resulting bitrate (all else held equal) and typically the higher quality the video (all else held equal).
This intra frame interpolation is the source of most artifacting in videos. It also has the side effect that when working with editing software instead of deciding a single frame to show you the image you’re looking at, your computer must decode the previous i-frame, and potentially the next b-frame, and then compute all of the deltas from the i-frame and b-frames and the intermediate frames until it gets to the frame you are on. This is a relatively taxing process and leads to pretty slow editing.
Enter All-I codecs, where every single frame is an i-frame and it isn’t dependent at all on what came before it and what comes after it. These are crisp, clear, lacking any artifacting from motion artifacts that weren’t encoded correctly from the frames that came before or after. And importantly, all-i codecs can be decoded with relative ease compared to interframe codecs.
It’s very common to shoot in all-i when doing professional video work. But it is also pretty useless to people not doing any editing.
All-i codecs like motion jpeg are actually typically withheld by manufacturers and only offered on their highest end camera. Example: Panasonic S1 and S1R offer no all-i codecs. You can only get that on the S1H (or also their GH5) and varicams.
On Sony cameras, to get access to their XAVC-I codec (their all-i codec) you have to step up to the FS7/FX9 series of professional video cameras.
Canon offers this on the EOS R and 5D IV, which is one of the reasons many people appreciate those cameras for video work.
Feb 23, 2020 at 09:09 AM
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