Getting the pssh data from a encrypted mp4

[peekaboo]

When I run

mp4dump --verbosity 3 --format json XXX.mp4 > pssh.txt

it can get the hex code for the data that required to produce a full info PSSH. However, it will have a pretty big txt file.


[Attachment 78866 - Click to enlarge]

Any quick way to dump this info ?

[Obo]

Jep, at least if you just search for the PSSH. Posted several times already - here's my way:

import base64
import sys
from pywidevine import PSSH

def find_wv_pssh_offsets(raw: bytes) -> list:
    offsets = []
    offset = 0
    while True:
        offset = raw.find(b'pssh', offset)
        if offset == -1:
            break
        size = int.from_bytes(raw[offset-4:offset], byteorder='big')
        pssh_offset = offset - 4
        offsets.append(raw[pssh_offset:pssh_offset+size])
        offset += size
    return offsets

def to_pssh(content: bytes) -> list:
    wv_offsets = find_wv_pssh_offsets(content)
    return [base64.b64encode(wv_offset).decode() for wv_offset in wv_offsets]

def from_file(file_path: str) -> list:
    with open(file_path, 'rb') as f:
        buffer = f.read(2048) # 1_048_576)
    return to_pssh(buffer)

pssh_list = from_file(sys.argv[1])
target_pssh = None
for item in pssh_list:
    pssh = PSSH(item)
    if pssh.system_id == PSSH.SystemId.Widevine:
        print(pssh)

The "2048" in line 24 might be too small and might only work for "faststart MP4" where the moov atom is located at the very beginnig of the file. You can raise that number to e.g. 1 MB.

[peekaboo]

Jep, at least if you just search for the PSSH. Posted several times already - here's my way:

import base64
import sys
from pywidevine import PSSH

def find_wv_pssh_offsets(raw: bytes) -> list:
    offsets = []
    offset = 0
    while True:
        offset = raw.find(b'pssh', offset)
        if offset == -1:
            break
        size = int.from_bytes(raw[offset-4:offset], byteorder='big')
        pssh_offset = offset - 4
        offsets.append(raw[pssh_offset:pssh_offset+size])
        offset += size
    return offsets

def to_pssh(content: bytes) -> list:
    wv_offsets = find_wv_pssh_offsets(content)
    return [base64.b64encode(wv_offset).decode() for wv_offset in wv_offsets]

def from_file(file_path: str) -> list:
    with open(file_path, 'rb') as f:
        buffer = f.read(2048) # 1_048_576)
    return to_pssh(buffer)

pssh_list = from_file(sys.argv[1])
target_pssh = None
for item in pssh_list:
    pssh = PSSH(item)
    if pssh.system_id == PSSH.SystemId.Widevine:
        print(pssh)

The "2048" in line 24 might be too small and might only work for "faststart MP4" where the moov atom is located at the very beginnig of the file. You can raise that number to e.g. 1 MB.

My lazy..haha no idea for the keywords.

But works perfectly, for my case 4096 (2MB) is needed