Matroskademux fails to create caps for ACM audio

Submitted by Matej @Knopp

Link to original bug (#757583)

Description

Created attachment 314809
Patch

gst_riff_create_audio_caps expects codec data in strf, but matroskademux passes it as strd

Sample file

https://s3.amazonaws.com/MatejK/Samples/2001-start.mkv

Patch 314809, "Patch":
0001-matroskademux-pass-riff-codec-data-as-strf-not-strd.patch