cache: make backbuffer size configurable

Allow setting an arbitrary amount, instead of the fixed 50%.

This is nto striclty backwards compatible. The defaults don't change,
but the --cache/--cache-default options now set the readahead portion.
So in practice, users who configured this until now will see the
double amount of cache being used, _plus_ the 75MB default backbuffer
will be in use.

1 files changed, 1 insertions, 0 deletions

diff --git a/options/options.h b/options/options.h
index 5d8bd2ea09..3dcb783164 100644
--- a/options/options.h
+++ b/options/options.h
@@ -53,6 +53,7 @@ struct mp_cache_opts {
     int def_size;
     int initial;
     int seek_min;
+    int back_buffer;
     char *file;
     int file_max;
 };