This is more detail on compression and how the Inspire footage compares to what we already experience. Clearly capture quality, the type of encoding and quality of compression matter, so the following just provides some relative points of reference.
1080p at 30 frames per second and 24 bits per pixel with no compression at all contains over 1.4 Gbit/s of data. Obviously that is just a massive amount of data. But, you can compress the data a huge amount without affecting the quality in a perceivable way.
As a point of reference, jpeg compression of 10:1 is almost completely unnoticeable for most images. So, if we take that raw 1080p 30fps footage and compress each frame at 10:1 rate we end up with a data stream that is just about 140 Mbit/s.
Apple's ProRes format has a bitrate of 147 Mbit/s. This is about the same as the rough estimate I have above for unnoticeable compression. This is a level of compression suitable for general editing, color correcting, chroma keying, etc. For complex editing ProRes HQ has a 220 Mbit/s data rate and higher data rates exist for special effects work, etc.
So, roughly speaking, 140 Mbit/s can deliver near-perfect 1080p video visually and will allow most general editing without issue.
Here is a quick rundown of video bitrates for popular and well regarded compact cameras:
- The BlackMagic pocket cinema camera records 1080p at 220 Mbit/s.
- Panasonic's GH4 can record 1080p 30 at 200 Mbit/s and 4K at 100 Mbit/s.
- Panasonic's LX100 records 1080p at 28 Mbit/s and 4K at 100 Mbit/s.
- Sony's RX100 II records 1080p at 28 Mbit/s.
- The GoPro 4 records at a maximum bitrate of 60 Mbit/s.
- The Inspire records 1080p 30 at 30 Mbit/s and 4K at 60 Mbit/s.
For comparison purposes, here are bitrates for video delivery:
- Cable TV "HD" is delivered at 10-15 Mbit/s and as 1080i or 720p.
- Upload to Youtube and Vimeo is recommended to be around 15 Mbit/s prior to conversion.
- Netflix delivers 1080p at about 5.8 Mbit/s. Youtube and Vimeo deliver 1080p at roughly 4.5 Mbit/s.
Clearly the available delivery of "HD" video is highly compressed -- to a level that can significantly degrade the perceived video quality. Forget 4K. We can't get 1080p at all from most cable/TV providers and the "HD" signal we do get is very compressed. Online video is generally even worse.
As noted earlier, the bitrate is only part of the story, and the Inspire's recorded rate is comparable to compact cameras and the GoPro 4, is more than enough for upload to youtube or vimeo, and is higher than you get from most all cable/satellite TV providers.
If we consider the other factors (capture quality in particular), the Inspire is working with less than a high end compact camera (smaller chip, hence more noise) and is more comparable to the GoPro in this regard.
Technically the GoPro is providing a better file than the Inspire, in my view. But, for aerial work I really don't like the look of the GoPro fisheye lens. If I edit to correct that I have to throw away a lot of data. As a result, the Inspire's near-rectlinear lens is providing better effective results than a GoPro in my view.
However, the Inspire's results are not up to the quality of high-end compacts (RX100 II and LX100 in particular) and not even close to the GH4 or BlackMagic pocket cinema. Yet, given the convenience and ease of use that the Inspire offers I think the resulting video file is more than acceptable and likely more than needed for many purposes. It beats a GoPro setup for aerial work and offers a lot more convenience than a larger rig required to fly a materially better camera.