int block_align
number of bytes per packet if constant and known or 0 Used by some WAV based audio codecs...
int bits_per_coded_sample
bits per sample/pixel from the demuxer (needed for huffyuv).
enum AVMediaType codec_type
unsigned int codec_tag
fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').