Rewrote finding keyframes and seeking. The problem was that

in many situations, FindKeyframe() was unable to reliably
predict what frame Seek() would be able to seek to.
 * Refactored a new base class StreamBase from the old
   StreamCookie, renamed StreamCookie to just Stream.
 * In FindKeyframe(), Stream will create a "ghost" StreamBase
   instance. That one will be used to actually seek in the
   stream without modifying the AVFormatContext of the real
   Stream. From that we can tell what position we can /really/
   seek to. For AVIs mostly, it is important to still use
   av_index_search_timestamp(), since for many AVIs I tested,
   reading the next packet after seeking did not produce a
   timestamp, however the index entry contained just the correct
   one. If the next packet does contain a PTS, it will still
   override the index timestamp, though.
 * Contrary to my previous belief, there was still a locking
   problem with how MediaPlayer used the BMediaTracks. The video
   decoding thread and the playback manager both used
   FindKeyframe() without holding the same lock. We support this
   now by using one BLocker per Stream. (The source BDataIO is
   still protected by another single lock.) With the new ghost
   stream stuff, the locking problem became much more of a problem,
   previously the FindKeyframe() had a much rarer race condition
   which would only trip when the decoding thread would cause new
   index entries to be inserted into the index.
 * Use the same ByteIOContext buffer size that avformat would be
   using if it initialized the ByteIOContext through other API.
 * Don't leak the probe buffer in case of error.
 * Don't leak the ByteIOContext buffer in the end.
 * Do not discard other stream packets anymore, this makes the
   ASF demuxer happy and ASF files can now be seeked as well as
   with ffplay itself.

With these changes, all my MPEG test streams work. Some could be seeked
before, but would show bad artifacts. Some streams would completely loose
video after seeking once. My MPEG2 test stream works much better now,
although audio is slightly out of sync, unfortunately. All my test AVIs
work as good as before, MP4 and MKV still work perfectly. The single
test ASF I got is now perfectly seekable.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38807 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/media/plugins/ffmpeg/AVFormatReader.h

@@ -46,10 +46,10 @@ public:
 									media_header* mediaHeader);
 
 private:
-	class StreamCookie;
+			class Stream;
 
-			StreamCookie**		fStreams;
-			BLocker				fStreamLock;
+			Stream**			fStreams;
+			BLocker				fSourceLock;
 };