Classifying Your High Resolution Video
Introduction
Before you attempt to process your high resolution video, you first need to determine what type of video you're dealing with. At the most basic level, your video can be interlaced or progressive. If it's interlaced, you will want to discover the source of the interlacing. Interlacing can be caused by how the video was filmed, how it was produced for television, or how your capture card captured the video. (You can read my article about Interlacing for more information.)
You may need to have some VirtualDub plug-ins installed to complete this section. If you don't already have them, you can obtain these plug-ins from the VirtualDub Plug-ins section.
1) To begin, run VirtualDub, go to File - > Open Video File, make sure the "Automatically detect and load additional segments" box is checked, and open the video you captured. (The file name you want to open is usually "capture.00.avi" or "capture.avi".)
Check For Field Swapping
Full resolution video is composed of two fields, which are the odd and even lines in a video. Sometimes, a capture card will swap these two fields, making your video look very strange. The artifacts of field swapping look very much like interlacing artifacts, so you have to be careful. Below I will describe a method to determine if your video has its fields swapped.
1) Use VirtualDub's position slider to find a portion of your video with absolutely no motion in all or most of the frame. It's helpful if the scene contains diagonal lines/edges or text.
2) Look at the edges of non-moving objects and check to see if they look jagged or out of focus. Here is a sample image that compares a correct video to a field swapped video:
3) If you see what appears to be field swapping, click on Video -> Filters -> Add -> field swap. Then hit OK twice to return to the main VirtualDub window. Now use the left and right arrow keys to scroll through some frames in the no-motion scene. Watch the output pane in VirtualDub (the video on the right) while doing this. If the field swap filter fixes the jagged edges in your video, then your video was probably field swapped. You might want to verify this be testing other scenes in your video that have no motion. If the field swap filter doesn't fix/improve the edges in your video, then your video does not have field swapping.
4) If you've determined that your video is not field swapped, click on Video -> Filters, highlight the 'field swap' filter, click the Delete button, and hit OK to return to the main VirtualDub window. If you've found that your video is field swapped, you may leave the 'field swap' filter there for the rest of the sections in this page.
Note: If you've determined that your video is field swapped, future videos that you capture will probably be field swapped as well. (Field swapping is generally capture card dependent.)
You should now know which of these categories your video falls into:
A) Field swapped. Continue on to the next section.
B) Not field swapped. Continue on to the next section.
Check For Generic Interlacing
If swapping the fields didn't remove the artifacts in your video, then your source video was probably interlaced. Interlacing can be caused by a number of things, but right now we will just check to see if there is any interlacing.
1) Scroll through your video and locate a part with lots of continuous motion. Portions where the camera quickly pans across a scene are a good choice.
2) Look for horizontal lines in places where there is movement. Theses horizontal lines look similar to the teeth of a comb. Here is sample image that contains the horizontal lines (interlacing artifacts):
3) If you see horizontal lines during motion, then your source video is interlaced. If you don't see any horizontal lines in any part of the video, then your source video is probably progressive (non-interlaced). Progressive video doesn't need any special processing, so it's much easier to work with.
You should now know which of these categories your video falls into:
A) Has some sort of interlacing. Continue on to the next sections to determine what type of interlacing it is.
B) The video is progressive (non-interlaced). No further analysis is needed, scroll down to the section called "Conclusion".
Check For NTSC Telecining
If your video is NTSC (29.97 fps), it may have been run through a process
known as telecine. The NTSC telecine process converts videos filmed at 24
fps, such as most movies, to play on your television at 29.97 fps. The
NTSC telecine process creates interlacing artifacts, but they can be removed
non-destructively and the video can be restored to its original ~24 fps.
Therefore, it's always a good idea to check if your video has been NTSC
telecined. You can read more about telecined video at my Telecining
article.
Note: If your video is PAL or SECAM and not NTSC, then you can skip this
section. (You can read more about PAL/SECAM and NTSC video at my article
entitled NTSC Vs. PAL/SECAM.)
1) Scroll through your video and locate a part with lots of continuous motion. Portions where the camera quickly pans across a scene are probably the best choice.
2) Scroll frame-by-frame through the high motion part of your video and try to identify frames with and without interlacing artifacts (horizontal lines).
3) If you find a pattern in your video of 3 non-interlaced frames (no horizontal lines) followed by 2 interlaced frames (with horizontal lines), then your video has been telecined. (Here are some sample frame grabs of NTSC telecined video.) If your video consists entirely of non-interlaced or interlaced frames, then your video has not been NTSC telecined.
You should now know which of these categories your video falls into:
A) NTSC telecined. You may scroll down to the section called "Determine the Field Dominance". (Note: If you are working with a newer anime video, you may also want to read the section called "Other Causes of Interlacing", especially part C.)
B) Not NTSC telecined. Continue on to the next section.
Check For Field Shifting of PAL/SECAM Video
Note: This section should only be applicable to those whose video is PAL or SECAM (25 fps). Since I personally do not live in a country where PAL/SECAM video is used, this section is based upon what I've read. If something that I've written is incorrect, please contact me. (You can read more about PAL/SECAM and NTSC video at my article entitled NTSC Vs. PAL/SECAM.)
PAL/SECAM telecining, unlike NTSC telecining, generally does not produce duplicated fields that lead to interlacing artifacts. However, sometimes one field of the video is delayed (shifted), which does produce interlacing artifacts. From what I understand, this commonly occurs for movies, which are converted from 24 fps to run at 25 fps.
1) Scroll through your video and locate a part with lots of continuous motion. Portions where the camera quickly pans across a scene are a good choice.
2) Click on Video -> Filters -> Add, and double-click the filter labeled "telecide". (This filter can be obtained from my VirtualDub Plug-ins page.) The default options are fine, so hit OK twice to return to the main VirtualDub window.
3) Press the 'play output' button and watch the video in the output pane. (The play output button [>o] is the third button at the bottom of the VirtualDub window.) If the interlacing artifacts (horizontal lines) are no longer present in the video in the output pane, then your video suffers from field shifting. You can press the stop button, scroll to other parts in your video, and press the play output again to verify that your video really does suffer from this problem. If the interlacing artifacts are still present in your video, then your video probably wasn't field shifted.
You should now know which of these categories your video falls into:
A) Field shifted. No further analysis is needed, scroll down to the section called "Conclusion".
B) Not field shifted. Continue on to the next section.
Other Causes of Interlacing
If you've made it this far and haven't found that field swapping, NTSC telecining, or field shifting are effective in removing the interlacing artifacts (horizontal lines) from your video, then your video is mostly likely from a truly interlaced source. However, there are a couple of other possibilities for the format of your video. These possibilities aren't very common, so I will only briefly describe them.
A) Your capture card might have placed the fields of your video in an order that cannot be corrected by a simple field swap. This problem is made harder to diagnose when combined with other sources of interlacing, such as field shifting in PAL/SECAM video. To diagnose and correct this type of problem, you can use the Smart Deinterlacer filter. (This filter can be obtained from my VirtualDub Plug-ins page.) By using the Advanced Processing section of the filter, you can try to correct a variety of field-related problems. You can read the Smart Deinterlacer help file for more information about its features and settings.
B) Your source video might have been telecined with a method other than the standard 3:2 pulldown method of NTSC telecining. This is most commonly found in certain anime videos. You might be able to correct the problem with the Telecide filter, but this won't always work. If it doesn't, then you may have to treat your video as if it were from an interlaced source and run it through a deinterlacing filter.
C) Your video might be part interlaced and part progressive (non-interlaced) or telecined. This is also usually found in newer anime videos. If part of your video is telecined , you can try using the Telecide filter to eliminate the telecining. For the truly interlaced part of your video, you may have to use a deinterlacing filter.
Since these situations are rare and can be difficult to deal with, I don't describe how to handle them in my High Resolution Video Processing page. You may post a question on my Message Boards if you can't figure it out on your own. With that being said, you may continue on to the next section.
Video From a Truly Interlaced Source
If nothing written above seems to help remove the interlacing artifacts from your video, then your video is almost certainly from a truly interlaced source. This type of video is very common, so don't be surprised if yours falls into this category. Depending on your desired output format for the video, you may have to run your video through a deinterlacing filter to remove the interlacing artifacts. This process does create a loss in detail, which is why it's always best to check if your video can be fixed through one of the previously mentioned methods.
You should now know which of these categories your video falls into:
A) From a truly interlaced source. Continue reading.
B) Not from a truly interlaced source. Continue reading.
Determine the Field Dominance
The field dominance of an interlaced video dictates which field is supposed to be updated first. It's important to know the field dominance (aka field order) when you're producing video for display on a TV. For example, you need to know the field dominance when producing an interlaced SVCD. Additionally, you have to know the field dominance to properly bob deinterlace a video, and some inverse telecine functions require knowledge of the field dominance.
If you want to do something with your video that requires the proper field dominance, continue following this section. Otherwise, skip to the section called "Conclusion".
One way to determine the field dominance is to use an Avisynth script. You can visit the Software or Avisynth pages to obtain Avisynth or a guide to using it. Once you have Avisynth installed, download the following .zip file:
Extract the contents of the .zip file to the folder containing your AVI. Next run Notepad, select File -> Open, and open the 'fields.avs' file. Follow the instructions in the file, save it, and open the file in VirtualDub. Then play through part of the video and pay attention to the smoothness of the motion. (Note: The video will be vertically squished.) If the motion is very jerky, modify the 'ComplementParity' line as described in the .avs file and recheck the video in VirtualDub. When you find the setting that produces smooth motion, the .avs file will tell you which field is dominant.
You should now know the field dominance of your video. Continue reading.
Conclusion
If you've went through everything above, you should now know whether or not your video is field swapped, NTSC telecined, field shifted, or from a truly interlaced source. You will make use of this information in my High Resolution Video Processing page, so be sure to remember the characteristics of your video.
If you're in the middle of my guide to capturing, processing, and encoding video, then you may head over to my High Resolution Video Processing page.