Which PSSH is the right one?

[Quint]

I had a lot of successes in the past few weeks, but struggle at one site, that is a bit more complicated (with pre-json-token-request).
It seems to work (I get a suitable token and pass it the right way), but doesn't at last. To isolate what really is wrong, I first have to be sure to pass the right PSSH. As far as I learned here there are three ways to get the PSSH:

-directly out of the mpd if present
-via PSSHBox with the Default-KID from the mpd
-via mp4dump

All three methods give me (very) different results (and none works so far).
From where should I know which is the right PSSH and the correct method? I thought that the PSSH out of the mp4 itself (via mp4dump) should always be correct, but is that so?

EDIT: Even the fourth method with the script from here:
https://forum.videohelp.com/threads/407291-Wrong-PSSH#post2670334
gives me another different result, but doesn't work either.

[jack_666]

Quint wrote

All three methods give me (very) different results (and none works so far)

and also

-directly out of the mpd if present

The one from the mpd is the correct one


If unable to get keys, with pssh from mpd, then your challenge lies elsewhere.

[Quint]

Thanks a lot! Is that 100% sure? And can you explain why so? Especially: How can the one inside the mp4 can be incorrect?

[Quint]

Checked all 4 with the decoder. The one from the mpd is 99.8% the right one. DOn't understand why, but will use it. Thanks again.

[Quint]

Eme-Logger proved it 100% correct. Still don't understand, why there are all these differences, but will use the logger in future to make sure.

if someone knows why, I would still be very interested in learning that.

[ridibunda]

I've used 3 methods:

-directly out of the mpd if present
-via PSSHBox with the Default-KID from the mpd
-via EME Logger

I've never used mp4dump because I've never needed it.

I've never got 3 different PSSH's in 3 methods.

If you see no PSSH or no KID in MPD file, look at EME-Logger (Dev Tools-Console). It'll show you a short init data. But when you see a very very long init data, then you have to convert it into HEX format and look for the Widevine PSSH. You'll search for Widevine ID (edef8ba979d64acea3c827dcd51d21ed). And before it, there will be the PSSH header (0000003c70737368). PSSH begins with PSSH payload.

Let's say your PSSH is AAAAPHBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAABwIARIQAA ECAwQFBgcICQoLDA0ODxoDZm9vIgFk

If you convert it into HEX, you get 0000003c7073736800000000edef8ba979d64acea3c827dcd5 1d21ed0000001c08011210000102030405060708090a0b0c0d 0e0f1a03666f6f220164

PSSH box = PSSH header (0000003c70737368) + PSSH system ID (edef8ba979d64acea3c827dcd51d21ed) + 32-bit data size (0000001c) + PSSH payload (08011210000102030405060708090a0b0c0d0e0f1a03666f6 f220164)

PSSH payload = key request

Payload is the changeable part. Header and System ID are constant values.

Hope that helps you to understand Widevine issue.