File Size

Resolution:
Resolution affects the file size because of how many pixels there are in the frame. These are measured in PPI (pixels per inch). The more pixels per inch there are, then the higher the resolution will be but the larger the file size will be. This is because the file has to store more pixels so the file size has to increase in order to store them. eg is an image has 200 pixels it will have a higher resolution than an image with 100 pixels. HD offers 5 times more than SD.

Frame Rate:
Frame Rate affects the file size because of the amount of frames per second. The more frames per second there are, then the larger the file size will be. If there are less frames per second then the lower the file size will be. This is because there are less frames that need to be stored.

Audio Settings:
Audio Settings affect the file size because of the high or low quality of the audio. The better the audio quality, then the larger the file needs to be to store it. If it is a low quality audio then the file size will not need to be as large to be able to store it. "In most cases you can use the default audio bitrate of 64k. If you need quality stereo sound, use 128k or 192k. For home DVD systems use up to 320k, assuming that your source video has appropriate audio quality. Bit rate/filesize mapping is simple. The size of the audio stream is the audio bitrate multiplied by the duration and divided by 8: size (bytes) = bitrate (bps) * duration (sec) / 8 ." -encoding.com