579 lines
20 KiB
C
579 lines
20 KiB
C
/*
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* Utility functions for seeking for use within FFmpeg format handlers.
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*
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* Copyright (c) 2009 Ivan Schreter
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "seek.h"
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#include "libavutil/mem.h"
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// NOTE: implementation should be moved here in another patch, to keep patches
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// separated.
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extern void av_read_frame_flush(AVFormatContext *s);
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/**
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* Helper structure to store parser state of AVStream.
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*/
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typedef struct AVStreamState {
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// Saved members of AVStream
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AVCodecParserContext *parser;
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AVPacket cur_pkt;
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int64_t last_IP_pts;
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int64_t cur_dts;
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int64_t reference_dts;
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const uint8_t *cur_ptr;
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int cur_len;
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int probe_packets;
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} AVStreamState;
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/**
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* Helper structure to store parser state of AVFormat.
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*/
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struct AVParserState {
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int64_t fpos; ///< File position at the time of call.
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// Saved members of AVFormatContext
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AVStream *cur_st; ///< Current stream.
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AVPacketList *packet_buffer; ///< Packet buffer of original state.
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AVPacketList *raw_packet_buffer; ///< Raw packet buffer of original state.
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int raw_packet_buffer_remaining_size; ///< Remaining size available for raw_packet_buffer.
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// Saved info for streams.
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int nb_streams; ///< Number of streams with stored state.
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AVStreamState *stream_states; ///< States of individual streams (array).
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};
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/**
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* Helper structure describing keyframe search state of one stream.
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*/
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typedef struct {
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int64_t pos_lo; ///< Position of the frame with low timestamp in file or INT64_MAX if not found (yet).
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int64_t ts_lo; ///< Frame presentation timestamp or same as pos_lo for byte seeking.
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int64_t pos_hi; ///< Position of the frame with high timestamp in file or INT64_MAX if not found (yet).
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int64_t ts_hi; ///< Frame presentation timestamp or same as pos_hi for byte seeking.
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int64_t last_pos; ///< Last known position of a frame, for multi-frame packets.
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int64_t term_ts; ///< Termination timestamp (which TS we already read).
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AVRational term_ts_tb; ///< Timebase for term_ts.
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int64_t first_ts; ///< First packet timestamp in this iteration (to fill term_ts later).
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AVRational first_ts_tb;///< Timebase for first_ts.
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int terminated; ///< Termination flag for current iteration.
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} AVSyncPoint;
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/**
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* Compare two timestamps exactly, taking into account their respective time bases.
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*
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* @param ts_a timestamp A.
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* @param tb_a time base for timestamp A.
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* @param ts_b timestamp B.
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* @param tb_b time base for timestamp A.
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* @return -1. 0 or 1 if timestamp A is less than, equal or greater than timestamp B.
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*/
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static int compare_ts(int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b)
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{
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int64_t a, b, res;
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if (ts_a == INT64_MIN)
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return ts_a < ts_b ? -1 : 0;
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if (ts_a == INT64_MAX)
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return ts_a > ts_b ? 1 : 0;
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if (ts_b == INT64_MIN)
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return ts_a > ts_b ? 1 : 0;
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if (ts_b == INT64_MAX)
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return ts_a < ts_b ? -1 : 0;
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a = ts_a * tb_a.num * tb_b.den;
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b = ts_b * tb_b.num * tb_a.den;
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res = a - b;
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if (res == 0)
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return 0;
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else
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return (res >> 63) | 1;
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}
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/**
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* Compute a distance between timestamps.
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*
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* Distances are only comparable, if same time bases are used for computing
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* distances.
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*
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* @param ts_hi high timestamp.
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* @param tb_hi high timestamp time base.
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* @param ts_lo low timestamp.
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* @param tb_lo low timestamp time base.
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* @return representation of distance between high and low timestamps.
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*/
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static int64_t ts_distance(int64_t ts_hi, AVRational tb_hi, int64_t ts_lo, AVRational tb_lo)
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{
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int64_t hi, lo;
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hi = ts_hi * tb_hi.num * tb_lo.den;
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lo = ts_lo * tb_lo.num * tb_hi.den;
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return hi - lo;
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}
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/**
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* Partial search for keyframes in multiple streams.
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*
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* This routine searches for the next lower and next higher timestamp to
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* given target timestamp in each stream, starting at current file position
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* and ending at position, where all streams have already been examined
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* (or when all higher key frames found in first iteration).
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*
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* This routine is called iteratively with exponential backoff to find lower
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* timestamp.
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*
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* @param s format context.
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* @param timestamp target timestamp (or position, if AVSEEK_FLAG_BYTE).
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* @param timebase time base for timestamps.
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* @param flags seeking flags.
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* @param sync array with information per stream.
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* @param keyframes_to_find count of keyframes to find in total.
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* @param found_lo pointer to count of already found low timestamp keyframes.
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* @param found_hi pointer to count of already found high timestamp keyframes.
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* @param first_iter flag for first iteration.
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*/
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static void search_hi_lo_keyframes(AVFormatContext *s,
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int64_t timestamp,
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AVRational timebase,
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int flags,
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AVSyncPoint *sync,
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int keyframes_to_find,
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int *found_lo,
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int *found_hi,
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int first_iter)
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{
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AVPacket pkt;
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AVSyncPoint *sp;
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AVStream *st;
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int idx;
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int flg;
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int terminated_count = 0;
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int64_t pos;
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int64_t pts, dts; // PTS/DTS from stream
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int64_t ts; // PTS in stream-local time base or position for byte seeking
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AVRational ts_tb; // Time base of the stream or 1:1 for byte seeking
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for (;;) {
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if (av_read_frame(s, &pkt) < 0) {
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// EOF or error, make sure high flags are set
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for (idx = 0; idx < s->nb_streams; ++idx) {
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if (s->streams[idx]->discard < AVDISCARD_ALL) {
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sp = &sync[idx];
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if (sp->pos_hi == INT64_MAX) {
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// No high frame exists for this stream
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(*found_hi)++;
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sp->ts_hi = INT64_MAX;
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sp->pos_hi = INT64_MAX - 1;
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}
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}
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}
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break;
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}
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idx = pkt.stream_index;
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st = s->streams[idx];
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if (st->discard >= AVDISCARD_ALL) {
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// This stream is not active, skip packet.
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continue;
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}
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sp = &sync[idx];
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flg = pkt.flags;
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pos = pkt.pos;
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pts = pkt.pts;
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dts = pkt.dts;
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if (pts == AV_NOPTS_VALUE) {
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// Some formats don't provide PTS, only DTS.
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pts = dts;
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}
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av_free_packet(&pkt);
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// Multi-frame packets only return position for the very first frame.
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// Other frames are read with position == -1. Therefore, we note down
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// last known position of a frame and use it if a frame without
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// position arrives. In this way, it's possible to seek to proper
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// position. Additionally, for parsers not providing position at all,
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// an approximation will be used (starting position of this iteration).
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if (pos < 0) {
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pos = sp->last_pos;
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} else {
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sp->last_pos = pos;
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}
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// Evaluate key frames with known TS (or any frames, if AVSEEK_FLAG_ANY set).
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if (pts != AV_NOPTS_VALUE && ((flg & PKT_FLAG_KEY) || (flags & AVSEEK_FLAG_ANY))) {
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if (flags & AVSEEK_FLAG_BYTE) {
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// For byte seeking, use position as timestamp.
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ts = pos;
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ts_tb.num = 1;
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ts_tb.den = 1;
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} else {
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// Get stream time_base.
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ts = pts;
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ts_tb = st->time_base;
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}
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if (sp->first_ts == AV_NOPTS_VALUE) {
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// Note down termination timestamp for the next iteration - when
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// we encounter a packet with the same timestamp, we will ignore
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// any further packets for this stream in next iteration (as they
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// are already evaluated).
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sp->first_ts = ts;
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sp->first_ts_tb = ts_tb;
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}
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if (sp->term_ts != AV_NOPTS_VALUE && compare_ts(ts, ts_tb, sp->term_ts, sp->term_ts_tb) > 0) {
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// We are past the end position from last iteration, ignore packet.
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if (!sp->terminated) {
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sp->terminated = 1;
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++terminated_count;
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if (sp->pos_hi == INT64_MAX) {
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// No high frame exists for this stream
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(*found_hi)++;
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sp->ts_hi = INT64_MAX;
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sp->pos_hi = INT64_MAX - 1;
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}
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if (terminated_count == keyframes_to_find)
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break; // all terminated, iteration done
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}
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continue;
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}
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if (compare_ts(ts, ts_tb, timestamp, timebase) <= 0) {
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// Keyframe found before target timestamp.
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if (sp->pos_lo == INT64_MAX) {
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// Found first keyframe lower than target timestamp.
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(*found_lo)++;
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sp->ts_lo = ts;
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sp->pos_lo = pos;
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} else if (sp->ts_lo < ts) {
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// Found a better match (closer to target timestamp).
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sp->ts_lo = ts;
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sp->pos_lo = pos;
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}
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}
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if (compare_ts(ts, ts_tb, timestamp, timebase) >= 0) {
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// Keyframe found after target timestamp.
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if (sp->pos_hi == INT64_MAX) {
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// Found first keyframe higher than target timestamp.
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(*found_hi)++;
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sp->ts_hi = ts;
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sp->pos_hi = pos;
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if (*found_hi >= keyframes_to_find && first_iter) {
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// We found high frame for all. They may get updated
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// to TS closer to target TS in later iterations (which
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// will stop at start position of previous iteration).
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break;
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}
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} else if (sp->ts_hi > ts) {
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// Found a better match (actually, shouldn't happen).
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sp->ts_hi = ts;
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sp->pos_hi = pos;
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}
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}
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}
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}
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// Clean up the parser.
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av_read_frame_flush(s);
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}
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int64_t ff_gen_syncpoint_search(AVFormatContext *s,
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int stream_index,
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int64_t pos,
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int64_t ts_min,
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int64_t ts,
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int64_t ts_max,
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int flags)
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{
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AVSyncPoint *sync, *sp;
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AVStream *st;
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int i;
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int keyframes_to_find = 0;
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int64_t curpos;
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int64_t step;
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int found_lo = 0, found_hi = 0;
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int64_t min_distance, distance;
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int64_t min_pos = 0;
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int first_iter = 1;
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AVRational time_base;
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if (flags & AVSEEK_FLAG_BYTE) {
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/* For byte seeking, we have exact 1:1 "timestamps" - positions */
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time_base.num = 1;
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time_base.den = 1;
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} else {
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if (stream_index >= 0) {
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/* We have a reference stream, which time base we use */
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st = s->streams[stream_index];
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time_base = st->time_base;
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} else {
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/* No reference stream, use AV_TIME_BASE as reference time base */
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time_base.num = 1;
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time_base.den = AV_TIME_BASE;
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}
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}
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// Initialize syncpoint structures for each stream.
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sync = (AVSyncPoint*) av_malloc(s->nb_streams * sizeof(AVSyncPoint));
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if (!sync) {
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// cannot allocate helper structure
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return -1;
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}
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for (i = 0; i < s->nb_streams; ++i) {
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st = s->streams[i];
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sp = &sync[i];
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sp->pos_lo = INT64_MAX;
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sp->ts_lo = INT64_MAX;
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sp->pos_hi = INT64_MAX;
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sp->ts_hi = INT64_MAX;
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sp->terminated = 0;
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sp->first_ts = AV_NOPTS_VALUE;
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sp->term_ts = ts_max;
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sp->term_ts_tb = time_base;
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sp->last_pos = pos;
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st->cur_dts = AV_NOPTS_VALUE;
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if (st->discard < AVDISCARD_ALL)
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++keyframes_to_find;
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}
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if (keyframes_to_find == 0) {
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// No stream active, error.
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av_free(sync);
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return -1;
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}
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// Find keyframes in all active streams with timestamp/position just before
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// and just after requested timestamp/position.
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step = 1024;
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curpos = pos;
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for (;;) {
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url_fseek(s->pb, curpos, SEEK_SET);
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search_hi_lo_keyframes(s,
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ts, time_base,
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flags,
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sync,
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keyframes_to_find,
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&found_lo, &found_hi,
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first_iter);
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if (found_lo == keyframes_to_find && found_hi == keyframes_to_find)
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break; // have all keyframes we wanted
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if (curpos == 0)
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break; // cannot go back anymore
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curpos = pos - step;
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if (curpos < 0)
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curpos = 0;
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step *= 2;
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// switch termination positions
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for (i = 0; i < s->nb_streams; ++i) {
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st = s->streams[i];
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st->cur_dts = AV_NOPTS_VALUE;
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sp = &sync[i];
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if (sp->first_ts != AV_NOPTS_VALUE) {
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sp->term_ts = sp->first_ts;
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sp->term_ts_tb = sp->first_ts_tb;
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sp->first_ts = AV_NOPTS_VALUE;
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}
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sp->terminated = 0;
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sp->last_pos = curpos;
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}
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first_iter = 0;
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}
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// Find actual position to start decoding so that decoder synchronizes
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// closest to ts and between ts_min and ts_max.
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pos = INT64_MAX;
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for (i = 0; i < s->nb_streams; ++i) {
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st = s->streams[i];
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if (st->discard < AVDISCARD_ALL) {
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sp = &sync[i];
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min_distance = INT64_MAX;
|
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// Find timestamp closest to requested timestamp within min/max limits.
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if (sp->pos_lo != INT64_MAX
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&& compare_ts(ts_min, time_base, sp->ts_lo, st->time_base) <= 0
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&& compare_ts(sp->ts_lo, st->time_base, ts_max, time_base) <= 0) {
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// low timestamp is in range
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min_distance = ts_distance(ts, time_base, sp->ts_lo, st->time_base);
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min_pos = sp->pos_lo;
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}
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if (sp->pos_hi != INT64_MAX
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&& compare_ts(ts_min, time_base, sp->ts_hi, st->time_base) <= 0
|
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&& compare_ts(sp->ts_hi, st->time_base, ts_max, time_base) <= 0) {
|
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// high timestamp is in range, check distance
|
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distance = ts_distance(sp->ts_hi, st->time_base, ts, time_base);
|
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if (distance < min_distance) {
|
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min_distance = distance;
|
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min_pos = sp->pos_hi;
|
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}
|
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}
|
|
if (min_distance == INT64_MAX) {
|
|
// no timestamp is in range, cannot seek
|
|
av_free(sync);
|
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return -1;
|
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}
|
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if (min_pos < pos)
|
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pos = min_pos;
|
|
}
|
|
}
|
|
|
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url_fseek(s->pb, pos, SEEK_SET);
|
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av_free(sync);
|
|
return pos;
|
|
}
|
|
|
|
AVParserState *ff_store_parser_state(AVFormatContext *s)
|
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{
|
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int i;
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AVStream *st;
|
|
AVStreamState *ss;
|
|
AVParserState *state = (AVParserState*) av_malloc(sizeof(AVParserState));
|
|
if (!state)
|
|
return NULL;
|
|
|
|
state->stream_states = (AVStreamState*) av_malloc(sizeof(AVStreamState) * s->nb_streams);
|
|
if (!state->stream_states) {
|
|
av_free(state);
|
|
return NULL;
|
|
}
|
|
|
|
state->fpos = url_ftell(s->pb);
|
|
|
|
// copy context structures
|
|
state->cur_st = s->cur_st;
|
|
state->packet_buffer = s->packet_buffer;
|
|
state->raw_packet_buffer = s->raw_packet_buffer;
|
|
state->raw_packet_buffer_remaining_size = s->raw_packet_buffer_remaining_size;
|
|
|
|
s->cur_st = NULL;
|
|
s->packet_buffer = NULL;
|
|
s->raw_packet_buffer = NULL;
|
|
s->raw_packet_buffer_remaining_size = RAW_PACKET_BUFFER_SIZE;
|
|
|
|
// copy stream structures
|
|
state->nb_streams = s->nb_streams;
|
|
for (i = 0; i < s->nb_streams; i++) {
|
|
st = s->streams[i];
|
|
ss = &state->stream_states[i];
|
|
|
|
ss->parser = st->parser;
|
|
ss->last_IP_pts = st->last_IP_pts;
|
|
ss->cur_dts = st->cur_dts;
|
|
ss->reference_dts = st->reference_dts;
|
|
ss->cur_ptr = st->cur_ptr;
|
|
ss->cur_len = st->cur_len;
|
|
ss->probe_packets = st->probe_packets;
|
|
ss->cur_pkt = st->cur_pkt;
|
|
|
|
st->parser = NULL;
|
|
st->last_IP_pts = AV_NOPTS_VALUE;
|
|
st->cur_dts = AV_NOPTS_VALUE;
|
|
st->reference_dts = AV_NOPTS_VALUE;
|
|
st->cur_ptr = NULL;
|
|
st->cur_len = 0;
|
|
st->probe_packets = MAX_PROBE_PACKETS;
|
|
av_init_packet(&st->cur_pkt);
|
|
}
|
|
|
|
return state;
|
|
}
|
|
|
|
void ff_restore_parser_state(AVFormatContext *s, AVParserState *state)
|
|
{
|
|
int i;
|
|
AVStream *st;
|
|
AVStreamState *ss;
|
|
av_read_frame_flush(s);
|
|
|
|
if (!state)
|
|
return;
|
|
|
|
url_fseek(s->pb, state->fpos, SEEK_SET);
|
|
|
|
// copy context structures
|
|
s->cur_st = state->cur_st;
|
|
s->packet_buffer = state->packet_buffer;
|
|
s->raw_packet_buffer = state->raw_packet_buffer;
|
|
s->raw_packet_buffer_remaining_size = state->raw_packet_buffer_remaining_size;
|
|
|
|
// copy stream structures
|
|
for (i = 0; i < state->nb_streams; i++) {
|
|
st = s->streams[i];
|
|
ss = &state->stream_states[i];
|
|
|
|
st->parser = ss->parser;
|
|
st->last_IP_pts = ss->last_IP_pts;
|
|
st->cur_dts = ss->cur_dts;
|
|
st->reference_dts = ss->reference_dts;
|
|
st->cur_ptr = ss->cur_ptr;
|
|
st->cur_len = ss->cur_len;
|
|
st->probe_packets = ss->probe_packets;
|
|
st->cur_pkt = ss->cur_pkt;
|
|
}
|
|
|
|
av_free(state->stream_states);
|
|
av_free(state);
|
|
}
|
|
|
|
static void free_packet_list(AVPacketList *pktl)
|
|
{
|
|
AVPacketList *cur;
|
|
while (pktl) {
|
|
cur = pktl;
|
|
pktl = cur->next;
|
|
av_free_packet(&cur->pkt);
|
|
av_free(cur);
|
|
}
|
|
}
|
|
|
|
void ff_free_parser_state(AVFormatContext *s, AVParserState *state)
|
|
{
|
|
int i;
|
|
AVStreamState *ss;
|
|
|
|
if (!state)
|
|
return;
|
|
|
|
for (i = 0; i < state->nb_streams; i++) {
|
|
ss = &state->stream_states[i];
|
|
if (ss->parser)
|
|
av_parser_close(ss->parser);
|
|
av_free_packet(&ss->cur_pkt);
|
|
}
|
|
|
|
free_packet_list(state->packet_buffer);
|
|
free_packet_list(state->raw_packet_buffer);
|
|
|
|
av_free(state->stream_states);
|
|
av_free(state);
|
|
}
|
|
|