import sys
p = sys.argv[1] if len(sys.argv) > 1 else '/tmp/cap.flv'
d = open(p, 'rb').read()
print('size', len(d))
if d[:3] != b'FLV':
    print('NOT FLV, first bytes:', d[:16].hex()); sys.exit(0)
off = int.from_bytes(d[5:9], 'big')
print('sig', d[:3], 'ver', d[3], 'flags', hex(d[4]), 'dataoffset', off)
i = off + 4  # skip PrevTagSize0
n = 0
while i + 11 <= len(d) and n < 14:
    ttype = d[i] & 0x1f
    dsize = int.from_bytes(d[i+1:i+4], 'big')
    body = d[i+11:i+11+dsize]
    info = ''
    if ttype == 9 and body:
        b0 = body[0]; isEx = (b0 & 0x80) != 0
        if isEx:
            ft = (b0 >> 4) & 7; pt = b0 & 0xf; fourcc = bytes(body[1:5])
            info = f'video EX frameType={ft} packetType={pt} fourcc={fourcc} head={body[:14].hex()}'
        else:
            cid = b0 & 0xf; ft = (b0 >> 4) & 0xf; avcpt = body[1] if len(body) > 1 else -1
            info = f'video LEGACY codecId={cid} frameType={ft} avcPacketType={avcpt} head={body[:14].hex()}'
    elif ttype == 18:
        info = 'script/meta'
    elif ttype == 8:
        info = 'audio'
    print(f'tag#{n} type={ttype} dsize={dsize} {info}')
    i = i + 11 + dsize + 4
    n += 1