Recently, I created a workflow for producing smooth looking slow motion video using my new Canon HV20...
(Sorry to all MAC users but this process was designed for PC...)
What you will be doing...
-Using an HDV video camera to produce fluid slow motion video footage that is of greater quality than a standard DVD
What I used to do this...
-Canon HV20 camcorder
-Sony Vegas 8.0
How I did this...
STEP #1. Record good quality & well lit video footage of a subject in motion
-record in regular HDV using shutter priority @ 1/60 sec. This shutter speed provides the correct motion blur characteristic
-DO NOT USE THE 24P SETTING
STEP #2. Using Vegas 8.0, capture the footage in it's native .m2t format
STEP #3. Using Vegas 8.0, render the video into an HDV 1440x1080 60i .avi file (label this file "HIGHSPEED.avi", you may change this later if you need)
-since this entire process requires several renders, the best method for preserving quality is to render with any compression at all. This may not be practical for some users because of the large file sizes involved. If you decide to use file compression, choose the highest quality settings possible and experiment as some codecs will work better then others. For the demo video, I used the DIVX PRO codec set to 6000kbs/single pass. Despite the high bitrate, compression artifacts can be seen built up from each level of the rendering process. The source video of the demo can be downloaded here http://www.vimeo.com/download/video:37448227 (right click "Save As" etc... it's about 100mb)
STEP #4. Use *AviSynth 2.5 to separate the even & odd video fields into a 1/60p, reduced resolution video stream (just google "AviSynth", it's free)
-There are other, more simple methods for this step but this is the one I use. The resolution of HDV footage is 1440x1080i. For this process, it's only the 1080i that we are interested in. For those of you who are not firmiliar with *video interlacing* here is a brief description...
-Each HDV video frame is made from 1080 "interlaced" lines of resolution.
-From top to bottom, the camera scans the the odd lines first... 1,3,5,7 etc... up to 1079, this scan takes 1/60 sec
-Then the camera goes back to the top and scans the even lines 2,4,6,8 etc... up to 1080, this scan takes 1/60 sec
-Depending on the camera model used, this order may be reversed... this is known as "field order"
-Each 1/30 sec video frame is made by combining these two 1/60 sec "fields" into one complete frame 1,2,3,4,5,6,7 etc...
It is important to understand how video interlacing works because it's the process of "deinterlacing" the video stream fields that is the key to creating a fluid slow motion video. We use AviSynth to deinterlace the two video fields into a single progressive video stream (1/60p). Doing this reduces the vertical resolution from 1080 to 540 (-50%). A small price to pay considering you still have all 1440 pixels of the horizontal resolution (more on that later...)
*What is AviSynth?
-AviSynth is a scripting tool for video post-production. It provides a unique way of editing and processing videos. AviSynth works as a frameserver, providing instant editing without the need for temporary files. AviSynth itself does not provide a graphical user interface (GUI), but instead relies on a script system. While this may at first seem tedious and unintuitive, it is a good way to manage projects in a precise, consistent, and reproducible manner. Because the text-based scripts are human readable, the scripting language is simple and complex filters can be created from basic operations to develop a sophisticated palette of useful and unique effects.
AviSynth uses the .AVS file format for storing the scripts. You can easily edit .AVS files using Windows "Notepad". Here are some script samples you will need...
This one seems to work well with the Canon HV20
if the video is jumpy or you are using a different model of HDV camera try this one...
-After you are finished editing the .AVS script with notepad name it "60FPS.avs" (this is just a sample name for the purpose this tutorial, you may change it)
-As I mentioned in section #3, the .AVI file name "HIGHSPEED.avi" can be changed to suit your project, just be sure to change it in the script too.
*THIS IS VERY IMPORTANT* you must now place your newly created "60FPS.avs" script file in the same folder as the source video, if you don't do this, the following step will not work.
STEP #5. Open the 60FPS.avs file with VirtualDub
-The .avs file you created in step #4 instructs VirtualDub to open the source video (which was 1440x1080 @ 60i) as 1440x540 @ 60p FPS (or 59.94 FPS to be more accurate but we will just round up to 60 to make it easier) Now, This is where we start to see the results. The video's aspect ratio will be distorted horizontally, this is normal and will be corrected.
-In VirtualDub press CTRL+R to open the "frame rate"panel (you can also find this under the "filter" menu in the edit bar)
-in the section "source rate adjustment" select "change to _____ frames per second" (add the frame rate you would like, 24 is optimal)
-Next, in the "frame rate conversion" section select "convert to fps_____ " (I use 24, you can use whatever your project requires)
-Now, Press CTRL+F to open up the "filter" section. This is the part where we correct the aspect ratio and resize the video.
-In the "filter" dialog box select "add" then select "resize" from the list of filters.
-In the "size options" section select "new size" as 960x540 (this is the mathematical optimized resolution, other sizes may reduce the quality)
-in the "aspect ratio" section select "disabled"
-in the "framing options" section select "do not letterbox or crop" then close window
-Save the video (press CTRL+P to select the compression codec of your choice) then F7 to open the "save as" window. Choose a name then save.
Here is a rundown of the benefits of the technique.
-The video is now 100% true progressive with a very "film like" quality. (the 1/60 sec shutter speed is critical for maximizing this effect)
-The video retains a quality level that significantly higher than standard DV footage (miniDV is 720x480i, this video is 960x540p)
-The video would still look fairly good resized to 1280x720p HD, a widely accepted standard for broadcasting and HD disc authoring
-The video can be slowed down even further in Vegas by using "frame interpolation/resampling" while still retaining a fluid look.
I hope all this wasn't too hard to follow for most of you. Your comments are welcome, enjoy!