from flashmedia import FLV, FLVError
from flashmedia.tag import ScriptData

# Open a FLV, pass any readable file-like object
try:
    flv = FLV(fd)
except FLVError as err:
    print("Invalid FLV")
    sys.exit()

# Iterate over tags
for tag in flv:
    # tag.data contains the parsed data, it's either a AudioData, VideoData or ScriptData object
    print("Tag with timestamp %d contains %s" % (tag.timestamp, repr(tag.data)))

    # Modify the metadata
    if isinstance(tag.data, ScriptData) and tag.data.name == "onMetaData":
        tag.data.value["description"] = "This file has been modified through python!"

    # Serialize the tag back into bytes
    data = tag.serialize()