In a previous post, I briefly discussed some of the specific concerns of working with footage from the Canon HV20. In this post, I will talk about these things in a little more depth, and with some example pictures to more fully demonstrate what I’m talking about.
Here is a full resolution frame-capture of a video stream shot with the HV20 (the image is a link to the full resolution image). All of the images posted here are compressed with jpeg 80% quality, and should have most of their original attributes preserved. Note that the pulldown has been removed with After Effects, and that this was originally a frame comprised of two interlaced fields. Note that this picture is HUGE (1920×1080), so if you have a regular sized monitor, expect to scroll around to look at it completely.
If you look closely at the image, you can discern fragments of interlacing artifacts left behind from the pulldown removal. This happens because the mpeg2 compression of the interlaced image results in fields that are imperfect with macroblocks and other imperfections. This confuses After Effects’ algorithms, leaving behind chunks of image that still have interlaced areas. Effectively this just looks like bits of the image have weird blocks of ‘liney’ areas. Below is a 4:1 crop of the above original frame, doubled in size.
You can notice these artifacts on the edge of the finger. In After Effects, there are plugins to process a frame to remove interlacing artifacts. With one of those applied, the image looks a little cleaner.
There are still noticeable artifacts from the mpeg2 compression. You can make out macroblocking and chroma abnormalities on the thumb and surrounding areas. If you were to look at the individual color channels, this would be more noticeable. Usually the compression artifacts are worse in the blue channel. There is a plugin that comes with the Magic Bullet Suite called the “Deartifactor” that takes a whack at removing compression artifacts such at as these.
Deartifacted:
Non-Deartifacted – Blue Channel Only:
Deartifacted – Blue Channel Only:
Sometimes it is hard to see what the deartifactor is doing in areas of detail. Here is another comparison in another less detailed area of the image.
Non-Deartifacted – Blue Channel Only:
Deartifacted – Blue Channel Only:
There is also a filter in After Effects called Remove Grain that was once sold as Grain Surgery by Visual Infinity, but is now included for free with After Effects. This plugin is quite amazingly good at removing grain while preserving detail in the image. While the compression artifacting is not quite grain, it does do a fair amount to improve the apparent image clarity, and while it does soften the image some, it can be adjusted for good results.
Remove Grain filter applied:
Here is the final processed image, in full resolution.
Most likely the effective qualitative differences in the image when viewed full-resolution are relatively minor. However, when you get into things like doing dramatic color correction or other processing, or attempting to extract a matte from an image using color keying, it is absolutely essential to have the best quality image that you can to work with. Of course it is not really a great idea to try to use HDV for something requiring excellent chroma key matte extraction, but for 800 dollars, this camera produces some amazing images, and you would be hard pressed to find a better solution for less than several thousand. There is also the possibility of capturing 4:2:2 uncompressed video before the MPEG2 compression stage from the HDMI output of this camera, if you have a Black Magic Intensity card, or an equivalent HDMI capture device, which could theoretically be plugged into a laptop. There has been some experimentation in this area, but little noticeable benefit is likely to be achieved.
As free alternatives for the post-processing of HDV, there is a plethora of possibility with AviSynth and various other freeware windows applications. There is quite a bit of activity around the area of using AviSynth for post-processing of HV20 footage.
The Farnsworth plus Sillyman Process
Automated 24p pulldown workflow using DGIndex and VirtualDubMod
Morgan MJPEG2000 as an alternative HD Intermediate Codec
AVISynth and VDub Templates / Code
To end this post, here are some other full-frame image-captures from the HV20, with no processing applied to them other than pulldown removal and deinterlacing.
An indoor image recorded in low light, showing the characteristic of the camera in high-gain mode, which can be avoided if operated properly.
An outdoor image from the camera on a relatively bright day.
Droplet Sunrise Explosion
Due to the inevitable migration of my sleep schedule during times without large quantities of obligation, I happened to be awake at about 7am one morning. I felt like going for a walk, for it had just stopped raining. The rain was the first in a couple of months. The sun was just rising behind some clouds, and the light looked quite pleasant. Armed with my Chinese macro extension tube, I took pictures of leaves and water droplets, and other inane subject matter. Brilliant.