Convert avchd to pgm

What is the difference between .avchd and .pgm?

Description: AVCHD (Advanced Video Coding High Definition) is a file format designed for recording and playing back high definition video. It is commonly used in digital camcorders and cameras for capturing HD footage. AVCHD leverages the MPEG-4 AVC/H.264 video compression codec, which efficiently reduces file sizes while preserving high-quality video resolution, and supports both Dolby AC-3 and linear PCM audio codecs for high-quality sound.; A PGM file is a grayscale image file saved in the portable gray map (PGM) format and encoded with one or two bytes (8 or 16 bits) per pixel. It contains header information and a grid of numbers that represent different shades of gray from black (0) to white (up to 65,536). PGM files are typically stored in ASCII text format, but also have a binary representation.