Is it possible to decrypt one mp4 file from the m3u8 list?

[Frankss]

For example I have a list:

#EXTM3U
#EXT-X-VERSION:6
#EXT-X-TARGETDURATION:6
#EXT-X-PLAYLIST-TYPE:EVENT
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PROGRAM-DATE-TIME:2024-03-10T17:19:56.899Z
#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,KEYFORMAT="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed",KEYFORMATVERSIONS="1",URI="data:text/plain;base64,AAAAMnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAABISEMLfwSCHWkius481X4OwC1g="
#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,KEYFORMAT="com.microsoft.playready",KEYFORMATVERSIONS="1",URI="data:text/plain;charset=UTF-16;base64,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"
#EXT-X-KEY:METHOD=SAMPLE-AES-CTR,KEYFORMAT="PRMNAGRA",KEYFORMATVERSIONS="1",URI="data:text/plain;base64,eyJrZXktaWQiOiJjMmRmYzEyMC04NzVhLTQ4YWUtYjM4Zi0zNTVmODNiMDBiNTgiLCJlbWkiOiJjdHIiLCJwcm0iOiJleUpqYjI1MFpXNTBTV1FpT2lKamRISWlMQ0pyWlhsSlpDSTZJbU15Wkdaak1USXdMVGczTldFdE5EaGhaUzFpTXpobUxUTTFOV1k0TTJJd01HSTFPQ0o5In0="
#EXT-X-MAP:URI="map.mp4"
#EXTINF:5.005,
070/17/19/56_899.mp4
#EXTINF:5.005,
070/17/20/01_904.mp4
...

I want to decrypt 01_904.mp4 the keyId and key are:

c2dfc120875a48aeb38f355f83b00b58
d6e7a7bedf7061b583dc97dde0777070

I've tried with mp4decrypt and the result is a 0kbs file.
The player only needs those two values, is in the keyId the info of the type of encryption, IV, etc to decrypt it?.

Thanks.

[Frankss]

I figured it out thank to the member shellcmd.

Two steps:

1) In cmd join the two files

copy /B map.mp4+01_904.mp4 encrypted.mp4

2) Decrypt

mp4decrypt --key 1:d6e7a7bedf7061b583dc97dde0777070 encrypted.mp4 decrypted.mp4

I wonder why the keyId isn't that important though, I put 1 instead and still the file get decrypted.

[[ss]vegeta]

I wonder why the keyId isn't that important though, I put 1 instead and still the file get decrypted.

I'm not sure it's the perfect analogy but it's like saying I wonder why IP address of websites aren't that important though, I put in google.com instead of 142.251.140.46 and I can still access the website!