avformat/aviobuf: don't reduce short seek threshold

Commit 8c8e5d5286 added a way to reduce
seek time by waiting for the windowed tcp packets instead of creating a
new socket connection. It implemented this by overwriting
s->short_seek_threshold in avio_seek(). However,
s->short_seek_threshold could already be set and be higher than the
threshold set by the protocol (i.e. s->short_seek_threshold is set in
ff_configure_buffers_for_index()).

This new feature was only enabled for tls connections in
70d8077b79. As in Ticket #9148 it reduced
performance because instead of waiting to refill the AVIOContext buffers
with an existing connections, a new HTTP request was often made instead.

Fixes Ticket #9148.

Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Andriy Gelman <andriy.gelman@gmail.com>

libavformat/aviobuf.c

@@ -283,13 +283,9 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
     if (offset < 0)
         return AVERROR(EINVAL);
 
-    if (s->short_seek_get) {
-        short_seek = s->short_seek_get(s->opaque);
-        /* fallback to default short seek */
-        if (short_seek <= 0)
-            short_seek = s->short_seek_threshold;
-    } else
     short_seek = s->short_seek_threshold;
+    if (s->short_seek_get)
+        short_seek = FFMAX(s->short_seek_get(s->opaque), short_seek);
 
     offset1 = offset - pos; // "offset1" is the relative offset from the beginning of s->buffer
     s->buf_ptr_max = FFMAX(s->buf_ptr_max, s->buf_ptr);