0,0 → 1,509 |
/* |
* seek utility functions for use within 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 |
*/ |
|
#include "seek.h" |
#include "libavutil/mathematics.h" |
#include "libavutil/mem.h" |
#include "internal.h" |
|
// NOTE: implementation should be moved here in another patch, to keep patches |
// separated. |
|
/** |
* helper structure describing keyframe search state of one stream |
*/ |
typedef struct { |
int64_t pos_lo; ///< position of the frame with low timestamp in file or INT64_MAX if not found (yet) |
int64_t ts_lo; ///< frame presentation timestamp or same as pos_lo for byte seeking |
|
int64_t pos_hi; ///< position of the frame with high timestamp in file or INT64_MAX if not found (yet) |
int64_t ts_hi; ///< frame presentation timestamp or same as pos_hi for byte seeking |
|
int64_t last_pos; ///< last known position of a frame, for multi-frame packets |
|
int64_t term_ts; ///< termination timestamp (which TS we already read) |
AVRational term_ts_tb; ///< timebase for term_ts |
int64_t first_ts; ///< first packet timestamp in this iteration (to fill term_ts later) |
AVRational first_ts_tb; ///< timebase for first_ts |
|
int terminated; ///< termination flag for the current iteration |
} AVSyncPoint; |
|
/** |
* Compute a distance between timestamps. |
* |
* Distances are only comparable, if same time bases are used for computing |
* distances. |
* |
* @param ts_hi high timestamp |
* @param tb_hi high timestamp time base |
* @param ts_lo low timestamp |
* @param tb_lo low timestamp time base |
* @return representation of distance between high and low timestamps |
*/ |
static int64_t ts_distance(int64_t ts_hi, |
AVRational tb_hi, |
int64_t ts_lo, |
AVRational tb_lo) |
{ |
int64_t hi, lo; |
|
hi = ts_hi * tb_hi.num * tb_lo.den; |
lo = ts_lo * tb_lo.num * tb_hi.den; |
|
return hi - lo; |
} |
|
/** |
* Partial search for keyframes in multiple streams. |
* |
* This routine searches in each stream for the next lower and the next higher |
* timestamp compared to the given target timestamp. The search starts at the current |
* file position and ends at the file position, where all streams have already been |
* examined (or when all higher key frames are found in the first iteration). |
* |
* This routine is called iteratively with an exponential backoff to find the lower |
* timestamp. |
* |
* @param s format context |
* @param timestamp target timestamp (or position, if AVSEEK_FLAG_BYTE) |
* @param timebase time base for timestamps |
* @param flags seeking flags |
* @param sync array with information per stream |
* @param keyframes_to_find count of keyframes to find in total |
* @param found_lo ptr to the count of already found low timestamp keyframes |
* @param found_hi ptr to the count of already found high timestamp keyframes |
* @param first_iter flag for first iteration |
*/ |
static void search_hi_lo_keyframes(AVFormatContext *s, |
int64_t timestamp, |
AVRational timebase, |
int flags, |
AVSyncPoint *sync, |
int keyframes_to_find, |
int *found_lo, |
int *found_hi, |
int first_iter) |
{ |
AVPacket pkt; |
AVSyncPoint *sp; |
AVStream *st; |
int idx; |
int flg; |
int terminated_count = 0; |
int64_t pos; |
int64_t pts, dts; // PTS/DTS from stream |
int64_t ts; // PTS in stream-local time base or position for byte seeking |
AVRational ts_tb; // Time base of the stream or 1:1 for byte seeking |
|
for (;;) { |
if (av_read_frame(s, &pkt) < 0) { |
// EOF or error, make sure high flags are set |
for (idx = 0; idx < s->nb_streams; ++idx) { |
if (s->streams[idx]->discard < AVDISCARD_ALL) { |
sp = &sync[idx]; |
if (sp->pos_hi == INT64_MAX) { |
// no high frame exists for this stream |
(*found_hi)++; |
sp->ts_hi = INT64_MAX; |
sp->pos_hi = INT64_MAX - 1; |
} |
} |
} |
break; |
} |
|
idx = pkt.stream_index; |
st = s->streams[idx]; |
if (st->discard >= AVDISCARD_ALL) |
// this stream is not active, skip packet |
continue; |
|
sp = &sync[idx]; |
|
flg = pkt.flags; |
pos = pkt.pos; |
pts = pkt.pts; |
dts = pkt.dts; |
if (pts == AV_NOPTS_VALUE) |
// some formats don't provide PTS, only DTS |
pts = dts; |
|
av_free_packet(&pkt); |
|
// Multi-frame packets only return position for the very first frame. |
// Other frames are read with position == -1. Therefore, we note down |
// last known position of a frame and use it if a frame without |
// position arrives. In this way, it's possible to seek to proper |
// position. Additionally, for parsers not providing position at all, |
// an approximation will be used (starting position of this iteration). |
if (pos < 0) |
pos = sp->last_pos; |
else |
sp->last_pos = pos; |
|
// Evaluate key frames with known TS (or any frames, if AVSEEK_FLAG_ANY set). |
if (pts != AV_NOPTS_VALUE && |
((flg & AV_PKT_FLAG_KEY) || (flags & AVSEEK_FLAG_ANY))) { |
if (flags & AVSEEK_FLAG_BYTE) { |
// for byte seeking, use position as timestamp |
ts = pos; |
ts_tb.num = 1; |
ts_tb.den = 1; |
} else { |
// otherwise, get stream time_base |
ts = pts; |
ts_tb = st->time_base; |
} |
|
if (sp->first_ts == AV_NOPTS_VALUE) { |
// Note down termination timestamp for the next iteration - when |
// we encounter a packet with the same timestamp, we will ignore |
// any further packets for this stream in next iteration (as they |
// are already evaluated). |
sp->first_ts = ts; |
sp->first_ts_tb = ts_tb; |
} |
|
if (sp->term_ts != AV_NOPTS_VALUE && |
av_compare_ts(ts, ts_tb, sp->term_ts, sp->term_ts_tb) > 0) { |
// past the end position from last iteration, ignore packet |
if (!sp->terminated) { |
sp->terminated = 1; |
++terminated_count; |
if (sp->pos_hi == INT64_MAX) { |
// no high frame exists for this stream |
(*found_hi)++; |
sp->ts_hi = INT64_MAX; |
sp->pos_hi = INT64_MAX - 1; |
} |
if (terminated_count == keyframes_to_find) |
break; // all terminated, iteration done |
} |
continue; |
} |
|
if (av_compare_ts(ts, ts_tb, timestamp, timebase) <= 0) { |
// keyframe found before target timestamp |
if (sp->pos_lo == INT64_MAX) { |
// found first keyframe lower than target timestamp |
(*found_lo)++; |
sp->ts_lo = ts; |
sp->pos_lo = pos; |
} else if (sp->ts_lo < ts) { |
// found a better match (closer to target timestamp) |
sp->ts_lo = ts; |
sp->pos_lo = pos; |
} |
} |
if (av_compare_ts(ts, ts_tb, timestamp, timebase) >= 0) { |
// keyframe found after target timestamp |
if (sp->pos_hi == INT64_MAX) { |
// found first keyframe higher than target timestamp |
(*found_hi)++; |
sp->ts_hi = ts; |
sp->pos_hi = pos; |
if (*found_hi >= keyframes_to_find && first_iter) { |
// We found high frame for all. They may get updated |
// to TS closer to target TS in later iterations (which |
// will stop at start position of previous iteration). |
break; |
} |
} else if (sp->ts_hi > ts) { |
// found a better match (actually, shouldn't happen) |
sp->ts_hi = ts; |
sp->pos_hi = pos; |
} |
} |
} |
} |
|
// Clean up the parser. |
ff_read_frame_flush(s); |
} |
|
int64_t ff_gen_syncpoint_search(AVFormatContext *s, |
int stream_index, |
int64_t pos, |
int64_t ts_min, |
int64_t ts, |
int64_t ts_max, |
int flags) |
{ |
AVSyncPoint *sync, *sp; |
AVStream *st; |
int i; |
int keyframes_to_find = 0; |
int64_t curpos; |
int64_t step; |
int found_lo = 0, found_hi = 0; |
int64_t min_distance, distance; |
int64_t min_pos = 0; |
int first_iter = 1; |
AVRational time_base; |
|
if (flags & AVSEEK_FLAG_BYTE) { |
// for byte seeking, we have exact 1:1 "timestamps" - positions |
time_base.num = 1; |
time_base.den = 1; |
} else { |
if (stream_index >= 0) { |
// we have a reference stream, which time base we use |
st = s->streams[stream_index]; |
time_base = st->time_base; |
} else { |
// no reference stream, use AV_TIME_BASE as reference time base |
time_base.num = 1; |
time_base.den = AV_TIME_BASE; |
} |
} |
|
// Initialize syncpoint structures for each stream. |
sync = av_malloc(s->nb_streams * sizeof(AVSyncPoint)); |
if (!sync) |
// cannot allocate helper structure |
return -1; |
|
for (i = 0; i < s->nb_streams; ++i) { |
st = s->streams[i]; |
sp = &sync[i]; |
|
sp->pos_lo = INT64_MAX; |
sp->ts_lo = INT64_MAX; |
sp->pos_hi = INT64_MAX; |
sp->ts_hi = INT64_MAX; |
sp->terminated = 0; |
sp->first_ts = AV_NOPTS_VALUE; |
sp->term_ts = ts_max; |
sp->term_ts_tb = time_base; |
sp->last_pos = pos; |
|
st->cur_dts = AV_NOPTS_VALUE; |
|
if (st->discard < AVDISCARD_ALL) |
++keyframes_to_find; |
} |
|
if (!keyframes_to_find) { |
// no stream active, error |
av_free(sync); |
return -1; |
} |
|
// Find keyframes in all active streams with timestamp/position just before |
// and just after requested timestamp/position. |
step = s->pb->buffer_size; |
curpos = FFMAX(pos - step / 2, 0); |
for (;;) { |
avio_seek(s->pb, curpos, SEEK_SET); |
search_hi_lo_keyframes(s, |
ts, time_base, |
flags, |
sync, |
keyframes_to_find, |
&found_lo, &found_hi, |
first_iter); |
if (found_lo == keyframes_to_find && found_hi == keyframes_to_find) |
break; // have all keyframes we wanted |
if (!curpos) |
break; // cannot go back anymore |
|
curpos = pos - step; |
if (curpos < 0) |
curpos = 0; |
step *= 2; |
|
// switch termination positions |
for (i = 0; i < s->nb_streams; ++i) { |
st = s->streams[i]; |
st->cur_dts = AV_NOPTS_VALUE; |
|
sp = &sync[i]; |
if (sp->first_ts != AV_NOPTS_VALUE) { |
sp->term_ts = sp->first_ts; |
sp->term_ts_tb = sp->first_ts_tb; |
sp->first_ts = AV_NOPTS_VALUE; |
} |
sp->terminated = 0; |
sp->last_pos = curpos; |
} |
first_iter = 0; |
} |
|
// Find actual position to start decoding so that decoder synchronizes |
// closest to ts and between ts_min and ts_max. |
pos = INT64_MAX; |
|
for (i = 0; i < s->nb_streams; ++i) { |
st = s->streams[i]; |
if (st->discard < AVDISCARD_ALL) { |
sp = &sync[i]; |
min_distance = INT64_MAX; |
// Find timestamp closest to requested timestamp within min/max limits. |
if (sp->pos_lo != INT64_MAX |
&& av_compare_ts(ts_min, time_base, sp->ts_lo, st->time_base) <= 0 |
&& av_compare_ts(sp->ts_lo, st->time_base, ts_max, time_base) <= 0) { |
// low timestamp is in range |
min_distance = ts_distance(ts, time_base, sp->ts_lo, st->time_base); |
min_pos = sp->pos_lo; |
} |
if (sp->pos_hi != INT64_MAX |
&& av_compare_ts(ts_min, time_base, sp->ts_hi, st->time_base) <= 0 |
&& av_compare_ts(sp->ts_hi, st->time_base, ts_max, time_base) <= 0) { |
// high timestamp is in range, check distance |
distance = ts_distance(sp->ts_hi, st->time_base, ts, time_base); |
if (distance < min_distance) { |
min_distance = distance; |
min_pos = sp->pos_hi; |
} |
} |
if (min_distance == INT64_MAX) { |
// no timestamp is in range, cannot seek |
av_free(sync); |
return -1; |
} |
if (min_pos < pos) |
pos = min_pos; |
} |
} |
|
avio_seek(s->pb, pos, SEEK_SET); |
av_free(sync); |
return pos; |
} |
|
AVParserState *ff_store_parser_state(AVFormatContext *s) |
{ |
int i; |
AVStream *st; |
AVParserStreamState *ss; |
AVParserState *state = av_malloc(sizeof(AVParserState)); |
if (!state) |
return NULL; |
|
state->stream_states = av_malloc(sizeof(AVParserStreamState) * s->nb_streams); |
if (!state->stream_states) { |
av_free(state); |
return NULL; |
} |
|
state->fpos = avio_tell(s->pb); |
|
// copy context structures |
state->packet_buffer = s->packet_buffer; |
state->parse_queue = s->parse_queue; |
state->raw_packet_buffer = s->raw_packet_buffer; |
state->raw_packet_buffer_remaining_size = s->raw_packet_buffer_remaining_size; |
|
s->packet_buffer = NULL; |
s->parse_queue = 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->probe_packets = st->probe_packets; |
|
st->parser = NULL; |
st->last_IP_pts = AV_NOPTS_VALUE; |
st->cur_dts = AV_NOPTS_VALUE; |
st->reference_dts = AV_NOPTS_VALUE; |
st->probe_packets = MAX_PROBE_PACKETS; |
} |
|
return state; |
} |
|
void ff_restore_parser_state(AVFormatContext *s, AVParserState *state) |
{ |
int i; |
AVStream *st; |
AVParserStreamState *ss; |
ff_read_frame_flush(s); |
|
if (!state) |
return; |
|
avio_seek(s->pb, state->fpos, SEEK_SET); |
|
// copy context structures |
s->packet_buffer = state->packet_buffer; |
s->parse_queue = state->parse_queue; |
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->probe_packets = ss->probe_packets; |
} |
|
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; |
AVParserStreamState *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); |
} |
|
free_packet_list(state->packet_buffer); |
free_packet_list(state->parse_queue); |
free_packet_list(state->raw_packet_buffer); |
|
av_free(state->stream_states); |
av_free(state); |
} |