Unable to run MPEG-4 test cases

[lumag]

The MPEG4_VIDEO test cases require the reference decoder, which is not available and can't be built. Can the testsuite for MPEG-4 be reworked to not require non-available software?

[mdimopoulos]

At the moment the reference decoder binary is required at test runtime, because there are differences in its output in different platforms (x86_64, arm64).
Reference decoder needs to be compiled from https://standards.iso.org/ittf/PubliclyAvailableStandards/c039392_ISO_IEC_14496-5_2001_Amd%205_2004(E)_Reference_Software.zip

[ylatuya]

This PR #324 will help in that direction to support building the reference decoders for more platforms and architectures