Additional Tools
One problem with using AviSynth is that you don't automatically get to see if your script creates the video you want. Fortunately, using a script editor like AvsP allows us to easily preview our video by using the external player (VirtualDub) that we used to demux the audio. Like before, you can either select External Player from the Video menu or press the [F6] key on your keyboard and it will open VirtualDub with the output of your script loaded.
It's a good idea to preview every script you write with AvsP, at least until you feel comfortable with both AviSynth and the AvsP interface. You can even retrieve error messages this way. Many simple errors are output as video to help you track down syntax problems.
Info
Just as the name suggests, you get a lot of information about your video by using AviSynth's built-in Info filter. It outputs several video properties over the video. If you have questions about basic properties of a clip you can often use it to find them. Be careful about where you place Info in a script. If you change properties (like deinterlacing or cutting out frames) you can get information that isn't correct for the final output. It doesn't take any arguments, so using it in a script is as simple as adding this line:
Info()
Make sure you remove Info from the script before encoding it in the next step.
Comments
You can designate comments with the # symbol. Everything to the end of the line after # is ignored as a comment. If you want to experiment with the effects of different filters, it's sometimes useful to have alternate sets of filters in a file. Commenting them out allows you to quickly and easily add or remove them.
