dilim/FFmpeg
1
0 Fork 0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2026-11-06 13:28:17 +00:00
Code Issues Packages Projects Releases Wiki Activity
Files
7aab64c1f2187a3d4607b699eb18810bbd806387
FFmpeg/libavformat/seek.c
T
Romain Beauxis d19f86ff4c avformat: discard the priming or the seek pre-roll after a seek 
After avformat_seek_file(), the decoder is not told what to discard
from what it decodes: the frames over the pre-roll are not reliable,
and a seek that lands inside the priming at the start of the stream
outputs the rest of it. Only some demuxers, such as mov, set the skip
for the priming themselves.

Mark the streams after a successful seek, and on the first packet of
each audio stream, add to the samples to skip, which the decoder applies
through AV_PKT_DATA_SKIP_SAMPLES:
- on the first packet of the stream, the priming, as when decoding from
  the start: its exact count when it is known;
- on any other packet, the larger of the rest of the priming, which ends
  at the start time of the stream, and the seek pre-roll of the codec,
  as the decoder misses what came before. After the priming of a stream
  whose start the seek targets, no pre-roll is added, as which packet
  comes first then depends on the demuxer. Each stream compares the
  target with its own start.

The first packet is only recognised when the demuxer knows the first
timestamp of the stream, such as after avformat_find_stream_info();
otherwise, the packet gets the pre-roll as after any seek. The priming
needs the timestamp of the packet and the start time of the stream, the
pre-roll does not. The skip may span several packets, as the decoder
carries it over the frames it outputs. Side data the demuxer set on the
packet is kept: the larger skip is used, and its padding at the end of
the stream is not overwritten.

The skip supplies the pre-roll the stream declares, whatever the demuxer
landed on; recovery beyond it depends on the codec and the bitstream.
The caller keeps or trims what is decoded after it as it wishes.

The decoding of the tests without accurate seek now starts one frame
later for AAC in MP4, CAF and ADTS, and two 2048 samples frames later
for HE-AAC in ADTS and with implicit SBR. A seek that lands on the last
packet of the priming of AAC in CAF, with 64 samples of it left, now
skips the 1024 samples of pre-roll instead of outputting that priming.
For Opus in Matroska, 3840 samples are skipped instead of the 312 the
decoder drops from its first frame, and the decoding with accurate seek
is cut on frames 24 samples, half a millisecond, earlier, within the
precision of the Matroska timestamps. A seek past the end of AAC in CAF
and Opus in Matroska skips the pre-roll on the last packet and keeps its
padding. A seek on the later of two streams, close to its start, adds
the pre-roll to the other stream, which is already past its own start.
A seek back to the start of Matroska now skips the exact priming on the
first packet: 312 samples for Opus and 481 for MP2.
2026-10-23 15:38:04 +00:00

849 lines
28 KiB
C
Raw Blame History

/*
* Seeking and index-related functions
* Copyright (c) 2000, 2001, 2002 Fabrice Bellard
*
* 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 <stdint.h>
#include "libavutil/avassert.h"
#include "libavutil/mathematics.h"
#include "libavutil/mem.h"
#include "libavutil/timestamp.h"
#include "libavcodec/avcodec.h"
#include "avformat.h"
#include "avformat_internal.h"
#include "avio_internal.h"
#include "demux.h"
#include "internal.h"
void avpriv_update_cur_dts(AVFormatContext *s, AVStream *ref_st, int64_t timestamp)
{
for (unsigned i = 0; i < s->nb_streams; i++) {
AVStream *const st = s->streams[i];
FFStream *const sti = ffstream(st);
sti->cur_dts =
av_rescale(timestamp,
st->time_base.den * (int64_t) ref_st->time_base.num,
st->time_base.num * (int64_t) ref_st->time_base.den);
}
}
void ff_reduce_index(AVFormatContext *s, int stream_index)
{
AVStream *const st = s->streams[stream_index];
FFStream *const sti = ffstream(st);
unsigned int max_entries = s->max_index_size / sizeof(AVIndexEntry);
if ((unsigned) sti->nb_index_entries >= max_entries) {
int i;
for (i = 0; 2 * i < sti->nb_index_entries; i++)
sti->index_entries[i] = sti->index_entries[2 * i];
sti->nb_index_entries = i;
}
}
int ff_add_index_entry(AVIndexEntry **index_entries,
int *nb_index_entries,
unsigned int *index_entries_allocated_size,
int64_t pos, int64_t timestamp,
int size, int distance, int flags)
{
AVIndexEntry *entries, *ie;
int index;
if ((unsigned) *nb_index_entries + 1 >= UINT_MAX / sizeof(AVIndexEntry))
return -1;
if (timestamp == AV_NOPTS_VALUE)
return AVERROR(EINVAL);
if (size < 0 || size > 0x3FFFFFFF)
return AVERROR(EINVAL);
if (is_relative(timestamp)) //FIXME this maintains previous behavior but we should shift by the correct offset once known
timestamp -= RELATIVE_TS_BASE;
entries = av_fast_realloc(*index_entries,
index_entries_allocated_size,
(*nb_index_entries + 1) *
sizeof(AVIndexEntry));
if (!entries)
return -1;
*index_entries = entries;
index = ff_index_search_timestamp(*index_entries, *nb_index_entries,
timestamp, AVSEEK_FLAG_ANY);
if (index < 0) {
index = (*nb_index_entries)++;
ie = &entries[index];
av_assert0(index == 0 || ie[-1].timestamp < timestamp);
} else {
ie = &entries[index];
if (ie->timestamp != timestamp) {
if (ie->timestamp <= timestamp)
return -1;
memmove(entries + index + 1, entries + index,
sizeof(AVIndexEntry) * (*nb_index_entries - index));
(*nb_index_entries)++;
} else if (ie->pos == pos && distance < ie->min_distance)
// do not reduce the distance
distance = ie->min_distance;
}
ie->pos = pos;
ie->timestamp = timestamp;
ie->min_distance = distance;
ie->size = size;
ie->flags = flags;
return index;
}
int av_add_index_entry(AVStream *st, int64_t pos, int64_t timestamp,
int size, int distance, int flags)
{
FFStream *const sti = ffstream(st);
timestamp = ff_wrap_timestamp(st, timestamp);
return ff_add_index_entry(&sti->index_entries, &sti->nb_index_entries,
&sti->index_entries_allocated_size, pos,
timestamp, size, distance, flags);
}
int ff_index_search_timestamp(const AVIndexEntry *entries, int nb_entries,
int64_t wanted_timestamp, int flags)
{
int a, b, m;
int64_t timestamp;
a = -1;
b = nb_entries;
// Optimize appending index entries at the end.
if (b && entries[b - 1].timestamp < wanted_timestamp)
a = b - 1;
while (b - a > 1) {
m = (a + b) >> 1;
// Search for the next non-discarded packet.
while ((entries[m].flags & AVINDEX_DISCARD_FRAME) && m < b && m < nb_entries - 1) {
m++;
if (m == b && entries[m].timestamp >= wanted_timestamp) {
m = b - 1;
break;
}
}
timestamp = entries[m].timestamp;
if (timestamp >= wanted_timestamp)
b = m;
if (timestamp <= wanted_timestamp)
a = m;
}
m = (flags & AVSEEK_FLAG_BACKWARD) ? a : b;
if (!(flags & AVSEEK_FLAG_ANY))
while (m >= 0 && m < nb_entries &&
!(entries[m].flags & AVINDEX_KEYFRAME))
m += (flags & AVSEEK_FLAG_BACKWARD) ? -1 : 1;
if (m == nb_entries)
return -1;
return m;
}
void ff_configure_buffers_for_index(AVFormatContext *s, int64_t time_tolerance)
{
int64_t pos_delta = 0;
int64_t skip = 0;
//We could use URLProtocol flags here but as many user applications do not use URLProtocols this would be unreliable
const char *proto = avio_find_protocol_name(s->url);
FFIOContext *ctx;
av_assert0(time_tolerance >= 0);
if (!proto) {
av_log(s, AV_LOG_INFO,
"Protocol name not provided, cannot determine if input is local or "
"a network protocol, buffers and access patterns cannot be configured "
"optimally without knowing the protocol\n");
}
if (proto && !(strcmp(proto, "file") && strcmp(proto, "pipe") && strcmp(proto, "cache")))
return;
for (unsigned ist1 = 0; ist1 < s->nb_streams; ist1++) {
AVStream *const st1 = s->streams[ist1];
FFStream *const sti1 = ffstream(st1);
for (unsigned ist2 = 0; ist2 < s->nb_streams; ist2++) {
AVStream *const st2 = s->streams[ist2];
FFStream *const sti2 = ffstream(st2);
if (ist1 == ist2)
continue;
for (int i1 = 0, i2 = 0; i1 < sti1->nb_index_entries; i1++) {
const AVIndexEntry *const e1 = &sti1->index_entries[i1];
int64_t e1_pts = av_rescale_q(e1->timestamp, st1->time_base, AV_TIME_BASE_Q);
if (e1->size < (1 << 23))
skip = FFMAX(skip, e1->size);
for (; i2 < sti2->nb_index_entries; i2++) {
const AVIndexEntry *const e2 = &sti2->index_entries[i2];
int64_t e2_pts = av_rescale_q(e2->timestamp, st2->time_base, AV_TIME_BASE_Q);
int64_t cur_delta;
if (e2_pts < e1_pts || e2_pts - (uint64_t)e1_pts < time_tolerance)
continue;
cur_delta = FFABS(e1->pos - e2->pos);
if (cur_delta < (1 << 23))
pos_delta = FFMAX(pos_delta, cur_delta);
break;
}
}
}
}
pos_delta *= 2;
ctx = ffiocontext(s->pb);
/* XXX This could be adjusted depending on protocol*/
if (s->pb->buffer_size < pos_delta) {
av_log(s, AV_LOG_VERBOSE, "Reconfiguring buffers to size %"PRId64"\n", pos_delta);
/* realloc the buffer and the original data will be retained */
if (ffio_realloc_buf(s->pb, pos_delta)) {
av_log(s, AV_LOG_ERROR, "Realloc buffer fail.\n");
return;
}
ctx->short_seek_threshold = FFMAX(ctx->short_seek_threshold, pos_delta/2);
}
ctx->short_seek_threshold = FFMAX(ctx->short_seek_threshold, skip);
}
int av_index_search_timestamp(AVStream *st, int64_t wanted_timestamp, int flags)
{
const FFStream *const sti = ffstream(st);
return ff_index_search_timestamp(sti->index_entries, sti->nb_index_entries,
wanted_timestamp, flags);
}
int avformat_index_get_entries_count(const AVStream *st)
{
return cffstream(st)->nb_index_entries;
}
const AVIndexEntry *avformat_index_get_entry(AVStream *st, int idx)
{
const FFStream *const sti = ffstream(st);
if (idx < 0 || idx >= sti->nb_index_entries)
return NULL;
return &sti->index_entries[idx];
}
const AVIndexEntry *avformat_index_get_entry_from_timestamp(AVStream *st,
int64_t wanted_timestamp,
int flags)
{
const FFStream *const sti = ffstream(st);
int idx = ff_index_search_timestamp(sti->index_entries,
sti->nb_index_entries,
wanted_timestamp, flags);
if (idx < 0)
return NULL;
return &sti->index_entries[idx];
}
static int64_t read_timestamp(AVFormatContext *s, int stream_index, int64_t *ppos, int64_t pos_limit,
int64_t (*read_timestamp)(struct AVFormatContext *, int , int64_t *, int64_t ))
{
int64_t ts = read_timestamp(s, stream_index, ppos, pos_limit);
if (stream_index >= 0)
ts = ff_wrap_timestamp(s->streams[stream_index], ts);
return ts;
}
int ff_seek_frame_binary(AVFormatContext *s, int stream_index,
int64_t target_ts, int flags)
{
const FFInputFormat *const avif = ffifmt(s->iformat);
int64_t pos_min = 0, pos_max = 0, pos, pos_limit;
int64_t ts_min, ts_max, ts;
int index;
int64_t ret;
AVStream *st;
FFStream *sti;
if (stream_index < 0)
return -1;
av_log(s, AV_LOG_TRACE, "read_seek: %d %s\n", stream_index, av_ts2str(target_ts));
ts_max =
ts_min = AV_NOPTS_VALUE;
pos_limit = -1; // GCC falsely says it may be uninitialized.
st = s->streams[stream_index];
sti = ffstream(st);
if (sti->index_entries) {
const AVIndexEntry *e;
/* FIXME: Whole function must be checked for non-keyframe entries in
* index case, especially read_timestamp(). */
index = av_index_search_timestamp(st, target_ts,
flags | AVSEEK_FLAG_BACKWARD);
index = FFMAX(index, 0);
e = &sti->index_entries[index];
if (e->timestamp <= target_ts || e->pos == e->min_distance) {
pos_min = e->pos;
ts_min = e->timestamp;
av_log(s, AV_LOG_TRACE, "using cached pos_min=0x%"PRIx64" dts_min=%s\n",
pos_min, av_ts2str(ts_min));
} else {
av_assert1(index == 0);
}
index = av_index_search_timestamp(st, target_ts,
flags & ~AVSEEK_FLAG_BACKWARD);
av_assert0(index < sti->nb_index_entries);
if (index >= 0) {
e = &sti->index_entries[index];
av_assert1(e->timestamp >= target_ts);
pos_max = e->pos;
ts_max = e->timestamp;
pos_limit = pos_max - e->min_distance;
av_log(s, AV_LOG_TRACE, "using cached pos_max=0x%"PRIx64" pos_limit=0x%"PRIx64
" dts_max=%s\n", pos_max, pos_limit, av_ts2str(ts_max));
}
}
pos = ff_gen_search(s, stream_index, target_ts, pos_min, pos_max, pos_limit,
ts_min, ts_max, flags, &ts, avif->read_timestamp);
if (pos < 0)
return -1;
/* do the seek */
if ((ret = avio_seek(s->pb, pos, SEEK_SET)) < 0)
return ret;
ff_read_frame_flush(s);
avpriv_update_cur_dts(s, st, ts);
return 0;
}
int ff_find_last_ts(AVFormatContext *s, int stream_index, int64_t *ts, int64_t *pos,
int64_t (*read_timestamp_func)(struct AVFormatContext *, int , int64_t *, int64_t ))
{
int64_t step = 1024;
int64_t limit, ts_max;
int64_t filesize = avio_size(s->pb);
int64_t pos_max = filesize - 1;
do {
limit = pos_max;
pos_max = FFMAX(0, (pos_max) - step);
ts_max = read_timestamp(s, stream_index,
&pos_max, limit, read_timestamp_func);
step += step;
} while (ts_max == AV_NOPTS_VALUE && 2*limit > step);
if (ts_max == AV_NOPTS_VALUE)
return -1;
for (;;) {
int64_t tmp_pos = pos_max + 1;
int64_t tmp_ts = read_timestamp(s, stream_index,
&tmp_pos, INT64_MAX, read_timestamp_func);
if (tmp_ts == AV_NOPTS_VALUE)
break;
av_assert0(tmp_pos > pos_max);
ts_max = tmp_ts;
pos_max = tmp_pos;
if (tmp_pos >= filesize)
break;
}
if (ts)
*ts = ts_max;
if (pos)
*pos = pos_max;
return 0;
}
int64_t ff_gen_search(AVFormatContext *s, int stream_index, int64_t target_ts,
int64_t pos_min, int64_t pos_max, int64_t pos_limit,
int64_t ts_min, int64_t ts_max,
int flags, int64_t *ts_ret,
int64_t (*read_timestamp_func)(struct AVFormatContext *,
int, int64_t *, int64_t))
{
FFFormatContext *const si = ffformatcontext(s);
int64_t pos, ts;
int64_t start_pos;
int no_change;
int ret;
av_log(s, AV_LOG_TRACE, "gen_seek: %d %s\n", stream_index, av_ts2str(target_ts));
if (ts_min == AV_NOPTS_VALUE) {
pos_min = si->data_offset;
ts_min = read_timestamp(s, stream_index, &pos_min, INT64_MAX, read_timestamp_func);
if (ts_min == AV_NOPTS_VALUE)
return -1;
}
if (ts_min >= target_ts) {
*ts_ret = ts_min;
return pos_min;
}
if (ts_max == AV_NOPTS_VALUE) {
if ((ret = ff_find_last_ts(s, stream_index, &ts_max, &pos_max, read_timestamp_func)) < 0)
return ret;
pos_limit = pos_max;
}
if (ts_max <= target_ts) {
*ts_ret = ts_max;
return pos_max;
}
av_assert0(ts_min < ts_max);
no_change = 0;
while (pos_min < pos_limit) {
av_log(s, AV_LOG_TRACE,
"pos_min=0x%"PRIx64" pos_max=0x%"PRIx64" dts_min=%s dts_max=%s\n",
pos_min, pos_max, av_ts2str(ts_min), av_ts2str(ts_max));
av_assert0(pos_limit <= pos_max);
if (no_change == 0) {
int64_t approximate_keyframe_distance = pos_max - pos_limit;
// interpolate position (better than dichotomy)
pos = av_rescale(target_ts - ts_min, pos_max - pos_min,
ts_max - ts_min) +
pos_min - approximate_keyframe_distance;
} else if (no_change == 1) {
// bisection if interpolation did not change min / max pos last time
pos = (pos_min + pos_limit) >> 1;
} else {
/* linear search if bisection failed, can only happen if there
* are very few or no keyframes between min/max */
pos = pos_min;
}
if (pos <= pos_min)
pos = pos_min + 1;
else if (pos > pos_limit)
pos = pos_limit;
start_pos = pos;
// May pass pos_limit instead of -1.
ts = read_timestamp(s, stream_index, &pos, INT64_MAX, read_timestamp_func);
if (pos == pos_max)
no_change++;
else
no_change = 0;
av_log(s, AV_LOG_TRACE, "%"PRId64" %"PRId64" %"PRId64" / %s %s %s"
" target:%s limit:%"PRId64" start:%"PRId64" noc:%d\n",
pos_min, pos, pos_max,
av_ts2str(ts_min), av_ts2str(ts), av_ts2str(ts_max), av_ts2str(target_ts),
pos_limit, start_pos, no_change);
if (ts == AV_NOPTS_VALUE) {
av_log(s, AV_LOG_ERROR, "read_timestamp() failed in the middle\n");
return -1;
}
if (target_ts <= ts) {
pos_limit = start_pos - 1;
pos_max = pos;
ts_max = ts;
}
if (target_ts >= ts) {
pos_min = pos;
ts_min = ts;
}
}
pos = (flags & AVSEEK_FLAG_BACKWARD) ? pos_min : pos_max;
ts = (flags & AVSEEK_FLAG_BACKWARD) ? ts_min : ts_max;
#if 0
pos_min = pos;
ts_min = read_timestamp(s, stream_index, &pos_min, INT64_MAX, read_timestamp_func);
pos_min++;
ts_max = read_timestamp(s, stream_index, &pos_min, INT64_MAX, read_timestamp_func);
av_log(s, AV_LOG_TRACE, "pos=0x%"PRIx64" %s<=%s<=%s\n",
pos, av_ts2str(ts_min), av_ts2str(target_ts), av_ts2str(ts_max));
#endif
*ts_ret = ts;
return pos;
}
static int seek_frame_byte(AVFormatContext *s, int stream_index,
int64_t pos, int flags)
{
FFFormatContext *const si = ffformatcontext(s);
int64_t pos_min, pos_max;
pos_min = si->data_offset;
pos_max = avio_size(s->pb) - 1;
if (pos < pos_min)
pos = pos_min;
else if (pos > pos_max)
pos = pos_max;
avio_seek(s->pb, pos, SEEK_SET);
s->io_repositioned = 1;
return 0;
}
static int seek_frame_generic(AVFormatContext *s, int stream_index,
int64_t timestamp, int flags)
{
FFFormatContext *const si = ffformatcontext(s);
AVStream *const st = s->streams[stream_index];
FFStream *const sti = ffstream(st);
const AVIndexEntry *ie;
int index;
int64_t ret;
index = av_index_search_timestamp(st, timestamp, flags);
if (index < 0 && sti->nb_index_entries &&
timestamp < sti->index_entries[0].timestamp)
return -1;
if (index < 0 || index == sti->nb_index_entries - 1) {
AVPacket *const pkt = si->pkt;
int nonkey = 0;
if (sti->nb_index_entries) {
av_assert0(sti->index_entries);
ie = &sti->index_entries[sti->nb_index_entries - 1];
if ((ret = avio_seek(s->pb, ie->pos, SEEK_SET)) < 0)
return ret;
s->io_repositioned = 1;
avpriv_update_cur_dts(s, st, ie->timestamp);
} else {
if ((ret = avio_seek(s->pb, si->data_offset, SEEK_SET)) < 0)
return ret;
s->io_repositioned = 1;
}
av_packet_unref(pkt);
for (;;) {
int read_status;
do {
read_status = av_read_frame(s, pkt);
} while (read_status == AVERROR(EAGAIN));
if (read_status < 0)
break;
if (stream_index == pkt->stream_index && pkt->dts > timestamp) {
if (pkt->flags & AV_PKT_FLAG_KEY) {
av_packet_unref(pkt);
break;
}
if (nonkey++ > 1000 && st->codecpar->codec_id != AV_CODEC_ID_CDGRAPHICS) {
av_log(s, AV_LOG_ERROR,"seek_frame_generic failed as this stream seems to contain no keyframes after the target timestamp, %d non keyframes found\n", nonkey);
av_packet_unref(pkt);
break;
}
}
av_packet_unref(pkt);
}
index = av_index_search_timestamp(st, timestamp, flags);
}
if (index < 0)
return -1;
ff_read_frame_flush(s);
if (ffifmt(s->iformat)->read_seek)
if (ffifmt(s->iformat)->read_seek(s, stream_index, timestamp, flags) >= 0)
return 0;
ie = &sti->index_entries[index];
if ((ret = avio_seek(s->pb, ie->pos, SEEK_SET)) < 0)
return ret;
s->io_repositioned = 1;
avpriv_update_cur_dts(s, st, ie->timestamp);
return 0;
}
static int seek_frame_internal(AVFormatContext *s, int stream_index,
int64_t timestamp, int flags)
{
AVStream *st;
int ret;
if (flags & AVSEEK_FLAG_BYTE) {
if (s->iformat->flags & AVFMT_NO_BYTE_SEEK)
return -1;
ff_read_frame_flush(s);
return seek_frame_byte(s, stream_index, timestamp, flags);
}
if (stream_index < 0) {
stream_index = av_find_default_stream_index(s);
if (stream_index < 0)
return -1;
st = s->streams[stream_index];
/* timestamp for default must be expressed in AV_TIME_BASE units */
timestamp = av_rescale(timestamp, st->time_base.den,
AV_TIME_BASE * (int64_t) st->time_base.num);
}
/* first, we try the format specific seek */
if (ffifmt(s->iformat)->read_seek) {
ff_read_frame_flush(s);
ret = ffifmt(s->iformat)->read_seek(s, stream_index, timestamp, flags);
} else
ret = -1;
if (ret >= 0)
return 0;
if (ffifmt(s->iformat)->read_timestamp &&
!(s->iformat->flags & AVFMT_NOBINSEARCH)) {
ff_read_frame_flush(s);
return ff_seek_frame_binary(s, stream_index, timestamp, flags);
} else if (!(s->iformat->flags & AVFMT_NOGENSEARCH)) {
ff_read_frame_flush(s);
return seek_frame_generic(s, stream_index, timestamp, flags);
} else
return -1;
}
int av_seek_frame(AVFormatContext *s, int stream_index,
int64_t timestamp, int flags)
{
int ret;
if (stream_index < -1 || stream_index >= (int)s->nb_streams)
return AVERROR(EINVAL);
if (ffifmt(s->iformat)->read_seek2 && !ffifmt(s->iformat)->read_seek) {
int64_t min_ts = INT64_MIN, max_ts = INT64_MAX;
if ((flags & AVSEEK_FLAG_BACKWARD))
max_ts = timestamp;
else
min_ts = timestamp;
return avformat_seek_file(s, stream_index, min_ts, timestamp, max_ts,
flags & ~AVSEEK_FLAG_BACKWARD);
}
ret = seek_frame_internal(s, stream_index, timestamp, flags);
if (ret >= 0)
ret = avformat_queue_attached_pictures(s);
return ret;
}
/**
* The largest pre-roll of the audio streams that are not discarded, in the
* units of the seek: the time base of the stream, or AV_TIME_BASE when no
* stream is given. Audio decoders need the frames before the target to
* produce reliable output at it, and declare how many samples in
* AVCodecParameters.seek_preroll.
*/
static int64_t seek_preroll(const AVFormatContext *s, int stream_index)
{
AVRational unit = stream_index >= 0 ? s->streams[stream_index]->time_base
: AV_TIME_BASE_Q;
int64_t preroll = 0;
for (unsigned i = 0; i < s->nb_streams; i++) {
const AVStream *st = s->streams[i];
const AVCodecParameters *par = st->codecpar;
int64_t v;
if (st->discard >= AVDISCARD_ALL)
continue;
if (par->codec_type != AVMEDIA_TYPE_AUDIO || par->seek_preroll <= 0 ||
par->sample_rate <= 0)
continue;
v = av_rescale_q_rnd(par->seek_preroll, (AVRational){ 1, par->sample_rate },
unit, AV_ROUND_UP);
preroll = FFMAX(preroll, v);
}
return preroll;
}
/**
* Ask the demuxer to discard the priming or the pre-roll from the first
* packet of each stream. A stream whose start the target does not pass
* is decoded from its start, which has no pre-roll to discard.
*/
static void request_seek_discard(AVFormatContext *s, int stream_index,
int64_t ts, int flags)
{
AVRational time_base = stream_index >= 0 ? s->streams[stream_index]->time_base
: AV_TIME_BASE_Q;
for (unsigned i = 0; i < s->nb_streams; i++) {
AVStream *const st = s->streams[i];
FFStream *const sti = ffstream(st);
sti->seek_discard = 1;
sti->seek_to_start = !(flags & (AVSEEK_FLAG_BYTE | AVSEEK_FLAG_FRAME)) &&
st->start_time != AV_NOPTS_VALUE &&
av_compare_ts(ts, time_base, st->start_time,
st->time_base) <= 0;
}
}
static int seek_file(AVFormatContext *s, int stream_index, int64_t min_ts,
int64_t ts, int64_t max_ts, int flags)
{
int dir;
int ret;
if (ffifmt(s->iformat)->read_seek2) {
ff_read_frame_flush(s);
if (stream_index == -1 && s->nb_streams == 1) {
ff_rescale_interval(AV_TIME_BASE_Q, s->streams[0]->time_base,
&min_ts, &ts, &max_ts);
stream_index = 0;
}
ret = ffifmt(s->iformat)->read_seek2(s, stream_index, min_ts,
ts, max_ts, flags);
if (ret >= 0)
ret = avformat_queue_attached_pictures(s);
return ret;
}
// Fall back on old API if new is not implemented but old is.
// Note the old API has somewhat different semantics.
dir = (ts - (uint64_t)min_ts > (uint64_t)max_ts - ts ? AVSEEK_FLAG_BACKWARD : 0);
ret = av_seek_frame(s, stream_index, ts, flags | dir);
if (ret < 0 && ts != min_ts && max_ts != ts) {
ret = av_seek_frame(s, stream_index, dir ? max_ts : min_ts, flags | dir);
if (ret >= 0)
ret = av_seek_frame(s, stream_index, ts, flags | (dir^AVSEEK_FLAG_BACKWARD));
}
return ret;
}
int avformat_seek_file(AVFormatContext *s, int stream_index, int64_t min_ts,
int64_t ts, int64_t max_ts, int flags)
{
int64_t target = ts, target_max = max_ts;
int ret;
if (min_ts > ts || max_ts < ts)
return -1;
if (stream_index < -1 || stream_index >= (int)s->nb_streams)
return AVERROR(EINVAL);
if (s->seek2any > 0)
flags |= AVSEEK_FLAG_ANY;
flags &= ~AVSEEK_FLAG_BACKWARD;
if (!(flags & (AVSEEK_FLAG_BYTE | AVSEEK_FLAG_FRAME))) {
int64_t preroll = seek_preroll(s, stream_index);
int64_t start = stream_index >= 0 ? s->streams[stream_index]->start_time
: s->start_time;
// Land early enough to decode the pre-roll, without leaving the
// range the caller asked for or going before the start.
target = FFMAX(av_sat_sub64(ts, preroll), min_ts);
if (start != AV_NOPTS_VALUE)
target = FFMAX(target, FFMIN(start, ts));
// Move the finite upper bound back by the same amount as the target.
// An open upper bound stays open.
if (max_ts != INT64_MAX)
target_max = av_sat_sub64(max_ts, av_sat_sub64(ts, target));
}
ret = seek_file(s, stream_index, min_ts, target, target_max, flags);
// Without a known start, the earlier target may come before the first
// packet.
if (ret < 0 && target != ts) {
target = ts;
ret = seek_file(s, stream_index, min_ts, ts, max_ts, flags);
}
if (ret >= 0)
request_seek_discard(s, stream_index, target, flags);
return ret;
}
/** Flush the frame reader. */
void ff_read_frame_flush(AVFormatContext *s)
{
ff_flush_packet_queue(s);
/* Reset read state for each stream. */
for (unsigned i = 0; i < s->nb_streams; i++) {
AVStream *const st = s->streams[i];
FFStream *const sti = ffstream(st);
if (sti->parser) {
av_parser_close(sti->parser);
sti->parser = NULL;
}
sti->last_IP_pts = AV_NOPTS_VALUE;
sti->last_dts_for_order_check = AV_NOPTS_VALUE;
if (sti->first_dts == AV_NOPTS_VALUE)
sti->cur_dts = RELATIVE_TS_BASE;
else
/* We set the current DTS to an unspecified origin. */
sti->cur_dts = AV_NOPTS_VALUE;
sti->probe_packets = s->max_probe_packets;
for (int j = 0; j < MAX_REORDER_DELAY + 1; j++)
sti->pts_buffer[j] = AV_NOPTS_VALUE;
sti->skip_samples = 0;
sti->seek_discard = 0;
}
}
int avformat_flush(AVFormatContext *s)
{
ff_read_frame_flush(s);
return 0;
}
void ff_rescale_interval(AVRational tb_in, AVRational tb_out,
int64_t *min_ts, int64_t *ts, int64_t *max_ts)
{
*ts = av_rescale_q (* ts, tb_in, tb_out);
*min_ts = av_rescale_q_rnd(*min_ts, tb_in, tb_out,
AV_ROUND_UP | AV_ROUND_PASS_MINMAX);
*max_ts = av_rescale_q_rnd(*max_ts, tb_in, tb_out,
AV_ROUND_DOWN | AV_ROUND_PASS_MINMAX);
// Rounding to the nearest can take the target out of the interval.
*ts = FFMAX(FFMIN(*ts, *max_ts), *min_ts);
}
Reference in new issue View Git Blame Copy Permalink