Support for generic multi-stream key frame finding for new seek API.

Originally committed as revision 19680 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 97 insertions, 0 deletions

diff --git a/libavformat/seek.h b/libavformat/seek.h
new file mode 100644
index 0000000000..570c2bcedf
--- /dev/null
+++ b/libavformat/seek.h
@@ -0,0 +1,97 @@
+/*
+ * Utility functions for seeking for use within FFmpeg format handlers.
+ *
+ * Copyright (c) 2009 Ivan Schreter
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVFORMAT_SEEK_H
+#define AVFORMAT_SEEK_H
+
+#include "avformat.h"
+
+/// Opaque structure for parser state.
+typedef struct AVParserState AVParserState;
+
+/**
+ * Search for sync point of all active streams.
+ *
+ * This is not supposed to be called directly by a user application,
+ * but by demuxers.
+ *
+ * A sync point is a point in stream, so that decoding from this point,
+ * output of decoders of all streams synchronizes closest to given timestamp
+ * ts (but taking timestamp limits into account, i.e., no sooner than ts_min
+ * and no later than ts_max).
+ *
+ * @param stream_index stream index for time base reference of timestamps.
+ * @param pos approximate position where to start searching for key frames.
+ * @param min_ts minimum allowed timestamp (position, if AVSEEK_FLAG_BYTE set).
+ * @param ts target timestamp (or position, if AVSEEK_FLAG_BYTE set in flags).
+ * @param max_ts maximum allowed timestamp (position, if AVSEEK_FLAG_BYTE set).
+ * @param flags if AVSEEK_FLAG_ANY is set, seek to any frame, otherwise only
+ *              to a keyframe. If AVSEEK_FLAG_BYTE is set, search by
+ *              position, not by timestamp.
+ * @return < 0 if no such sync point could be found, otherwise stream position
+ *              (stream is repositioned to this position).
+ */
+int64_t ff_gen_syncpoint_search(AVFormatContext *s,
+                                int stream_index,
+                                int64_t pos,
+                                int64_t min_ts,
+                                int64_t ts,
+                                int64_t max_ts,
+                                int flags);
+
+/**
+ * Store current parser state and file position.
+ *
+ * This function can be used by demuxers before destructive seeking algorithm
+ * to store parser state. After the seek, depending on outcome, original state
+ * can be restored or new state kept and original state freed.
+ *
+ * @note As a side effect, original parser state is reset, since structures
+ *       are relinked to stored state instead of being deeply-copied (for
+ *       performance reasons and to keep code simple).
+ *
+ * @param s context from which to save state.
+ * @return parser state object or NULL if memory could not be allocated.
+ */
+AVParserState *ff_store_parser_state(AVFormatContext *s);
+
+/**
+ * Restore previously saved parser state and file position.
+ *
+ * Saved state will be invalidated and freed by this call, since internal
+ * structures will be relinked back to stored state instead of being
+ * deeply-copied.
+ *
+ * @param s context to which to restore state (same as used for storing state).
+ * @param state state to restore.
+ */
+void ff_restore_parser_state(AVFormatContext *s, AVParserState *state);
+
+/**
+ * Free previously saved parser state.
+ *
+ * @param s context to which the state belongs (same as used for storing state).
+ * @param state state to free.
+ */
+void ff_free_parser_state(AVFormatContext *s, AVParserState *state);
+
+#endif /* AVFORMAT_SEEK_H */