Because it's kind of dumb. (But not sure if it was worth the trouble.)
For stream_file.c, we add new explicit fields. The rest are rather
special uses and can be killed by comparing the stream impl. name.
The changes to DVD/BD/CD/TV are entirely untested.
stream_edl merely makes demux_edl act "special", which checks for the
stream type explicitly and then does something with its URL. If a cache
is added before the stream, it'll try to use the cache's URL (i.e. an
empty string), and will then obviously fail to parse the URL. While this
is slightly stupid, just disabling the entirely useless cache is the
most effective solution.
Fixes#1378.
While I'm not very fond of "const", it's important for declarations
(it decides whether a symbol is emitted in a read-only or read/write
section). Fix all these cases, so we have writeable global data only
when we really need.
For some reason, we support writeable streams. (Only encoding uses that,
and the use of it looks messy enough that I want to replace it with FILE
or avio today.)
It's a chaos: most streams do not actually check the mode parameter like
they should. Simplify it, and let streams signal availability of write
mode by setting a flag in the stream info struct.
