Decryption not working with .webm video for MPD with video/audio keys

[TNAS123]

I came across this issue today. If you specify an MPD where source video is .webm, and audio/video encrypted with different keys - then N-m3u8DL-RE is not able to decrypt the video and mux files together. The audio is decrypting fine. It's like the tool does not know it can use a key on the video.

e.g.

• MPD

• Video (.webm) > kid1:key1
• Audio (m4a) > kid2:key2
• mux to mp4 or mkv
  = audio working, no video

If you use shaka-packager manually on the webm file, it decrypts ok. So I think the tool needs to support this format (webm) better for decryption.

[whitesnakeftw]

Same thing just happened to me with this:

N_m3u8DL-RE -mt --use-shaka-packager --key 63626465653765363339616330313832:61653836613537613039366561643735 "https://vcze131.cda.pl/2606897vp9/2606897.mpd"

Both video and audio are .webm and decryption seems to be skipped entirely. Using shaka packager manually on it works.

[whitesnakeftw]

@whitesnakeftw

Hello, excuse me. This 63626465653765363339616330313832 can be found in the mpd file, but where did the 61653836613537613039366561643735 data come from?

I used pywidevine to get the decryption key.

[hyww]

Root cause of this issue seems to be that key ID of .webm cannot be acquired using MP4DecryptUtil.ReadInit().

I've found a way to get key id using shaka-packager.

#401