At least Matroska files have a "forced" flag (in addition to the
"default" flag). Export this flag. Treat it almost like the default
flag, but with slightly higher priority.
This provides a new method for enabling spdif passthrough. The old
method via --ad (--ad=spdif:ac3 etc.) is deprecated. The deprecated
method will probably stop working at some point.
This also supports PCM fallback. One caveat is that it will lose at
least 1 audio packet in doing so. (I don't care enough to prevent this.)
(This is named after the old S/PDIF connector, because it uses the same
underlying technology as far as the higher level protoco is concerned.
Also, the user should be renamed that passthrough is backwards.)
This command has been deprecated in the 0.8.x and 0.9.x releases - get
rid of it. Its only point ever was MPlayer compatibility, which broke
years ago anyway.
Also replace their implementation with the recently introduced
properties. One significant difference is that audio-channels using OSD
formatting does not print the channel layout. The user can just use the
replacement property instead.
