avformat: Deprecate AVFMT_FLAG_PRIV_OPT, remove av_demuxer_open on bump

This flag was added in 492026209b9b58eaf6d2ea56423f6b1e1a8a76a5
in conjunction with av_demuxer_open() to allow to pass private
options to demuxers. It worked as follows: av_open_input_stream()
(the predecessor of avformat_open_input()) would not call the
read_header function if this flag is set. Instead the user could set
private options of the demuxer via the format's private class after
avformat_open_input() and then call av_demuxer_open() which called
the format's read_header function.

This approach was abandoned in e37f161e66e042d6c2c7470c4d9881df9427fc4a
and av_demuxer_open() deprecated; instead the AVDictionary based way of
passing private options to the demuxer was choosen. Yet
AVFMT_FLAG_PRIV_OPT has never been deprecated and av_demuxer_open()
never removed. This commit implements the deprecation of the flag and
schedules av_demuxer_open for removal on the next major bump.
Given that av_demuxer_open() has been deprecated in 2012 and that this
flag is useless without it, the flag will be ignored after the next
major version bump.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/doc/APIchanges b/doc/APIchanges
index a49e181c13..a003abf7ca 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -15,6 +15,10 @@ libavutil:     2017-10-21
 
 API changes, most recent first:
 
+2021-03-03 - xxxxxxxxxx - lavf 58.70.100 - avformat.h
+  Deprecate AVFMT_FLAG_PRIV_OPT. It will do nothing
+  as soon as av_demuxer_open() is removed.
+
 2021-02-27 - xxxxxxxxxx - lavc 58.126.100 - avcodec.h
   Deprecated avcodec_get_frame_class().