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lavf: Provide a monotonic timestamp to the outside world
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This detects and removes single timestamp wraps, which fixes seeking for affected video files.
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@axmhari
axmhari committed Dec 16, 2012
1 parent 99e0ce5 commit b2d3b83
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Showing 3 changed files with 151 additions and 10 deletions.
37 changes: 37 additions & 0 deletions lib/ffmpeg/libavformat/avformat.h
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Expand Up @@ -627,6 +627,13 @@ typedef struct AVIndexEntry {
#define AV_DISPOSITION_VISUAL_IMPAIRED 0x0100 /**< stream for visual impaired audiences */
#define AV_DISPOSITION_CLEAN_EFFECTS 0x0200 /**< stream without voice */

/*
* Options for behavior on timestamp wrap detection.
*/
#define AV_PTS_WRAP_IGNORE 0 ///< ignore the wrap
#define AV_PTS_WRAP_ADD_OFFSET 1 ///< add the format specific offset on wrap detection
#define AV_PTS_WRAP_SUB_OFFSET -1 ///< subtract the format specific offset on wrap detection

/**
* Stream structure.
* New fields can be added to the end with minor version bumps.
Expand Down Expand Up @@ -857,6 +864,24 @@ typedef struct AVStream {

int pts_wrap_bits; /**< number of bits in pts (used for wrapping control) */
#endif

/**
* Internal data to check for wrapping of the time stamp
*/
int64_t pts_wrap_reference;

/**
* Options for behavior, when a wrap is detected.
*
* Defined by AV_PTS_WRAP_ values.
*
* If correction is enabled, there are two possibilities:
* If the first time stamp is near the wrap point, the wrap offset
* will be subtracted, which will create negative time stamps.
* Otherwise the offset will be added.
*/
int pts_wrap_behavior;

} AVStream;

#define AV_PROGRAM_RUNNING 1
Expand All @@ -878,6 +903,10 @@ typedef struct AVProgram {
int program_num;
int pmt_pid;
int pcr_pid;

int64_t pts_wrap_reference; ///< reference dts for wrap detection
int pts_wrap_behavior; ///< behavior on wrap detection

} AVProgram;

#define AVFMTCTX_NOHEADER 0x0001 /**< signal that no header is present
Expand Down Expand Up @@ -1234,6 +1263,14 @@ typedef struct AVFormatContext {
/* av_seek_frame() support */
int64_t data_offset; /**< offset of the first packet */
#endif

/**
* Correct single timestamp overflows
* - encoding: unused
* - decoding: Set by user via AVOPtions (NO direct access)
*/
unsigned int correct_ts_overflow;

} AVFormatContext;

typedef struct AVPacketList {
Expand Down
1 change: 1 addition & 0 deletions lib/ffmpeg/libavformat/options.c
View file
Expand Up @@ -127,6 +127,7 @@ static const AVOption options[]={
{"careful", "consider things that violate the spec and have not been seen in the wild as errors", 0, AV_OPT_TYPE_CONST, {.dbl = AV_EF_CAREFUL }, INT_MIN, INT_MAX, D, "err_detect"},
{"compliant", "consider all spec non compliancies as errors", 0, AV_OPT_TYPE_CONST, {.dbl = AV_EF_COMPLIANT }, INT_MIN, INT_MAX, D, "err_detect"},
{"aggressive", "consider things that a sane encoder shouldnt do as an error", 0, AV_OPT_TYPE_CONST, {.dbl = AV_EF_AGGRESSIVE }, INT_MIN, INT_MAX, D, "err_detect"},
{"correct_ts_overflow", "correct single timestamp overflows", OFFSET(correct_ts_overflow), AV_OPT_TYPE_INT, {.dbl = 1}, 0, 1, D},
{NULL},
};

Expand Down
123 changes: 113 additions & 10 deletions lib/ffmpeg/libavformat/utils.c
View file
Expand Up @@ -122,6 +122,27 @@ static void frac_add(AVFrac *f, int64_t incr)
f->num = num;
}

/**
* Wrap a given time stamp, if there is an indication for an overflow
*
* @param st stream
* @param timestamp the time stamp to wrap
* @return resulting time stamp
*/
static int64_t wrap_timestamp(AVStream *st, int64_t timestamp)
{
if (st->pts_wrap_behavior != AV_PTS_WRAP_IGNORE &&
st->pts_wrap_reference != AV_NOPTS_VALUE && timestamp != AV_NOPTS_VALUE) {
if (st->pts_wrap_behavior == AV_PTS_WRAP_ADD_OFFSET &&
timestamp < st->pts_wrap_reference)
return timestamp + (1LL<<st->pts_wrap_bits);
else if (st->pts_wrap_behavior == AV_PTS_WRAP_SUB_OFFSET &&
timestamp >= st->pts_wrap_reference)
return timestamp - (1LL<<st->pts_wrap_bits);
}
return timestamp;
}

/** head of registered input format linked list */
static AVInputFormat *first_iformat = NULL;
/** head of registered output format linked list */
Expand Down Expand Up @@ -798,6 +819,8 @@ int av_read_packet(AVFormatContext *s, AVPacket *pkt)
}

st= s->streams[pkt->stream_index];
pkt->dts = wrap_timestamp(st, pkt->dts);
pkt->pts = wrap_timestamp(st, pkt->pts);

switch(st->codec->codec_type){
case AVMEDIA_TYPE_VIDEO:
Expand Down Expand Up @@ -948,8 +971,67 @@ static int is_intra_only(AVCodecContext *enc){
return 0;
}

static int update_wrap_reference(AVFormatContext *s, AVStream *st, int stream_index)
{
if (s->correct_ts_overflow && st->pts_wrap_bits != 64 &&
st->pts_wrap_reference == AV_NOPTS_VALUE && st->first_dts != AV_NOPTS_VALUE) {
int i;

// reference time stamp should be 60 s before first time stamp
int64_t pts_wrap_reference = st->first_dts - av_rescale(60, st->time_base.den, st->time_base.num);
// if first time stamp is not more than 1/8 and 60s before the wrap point, subtract rather than add wrap offset
int pts_wrap_behavior = (st->first_dts < (1LL<<st->pts_wrap_bits) - (1LL<<st->pts_wrap_bits-3)) ||
(st->first_dts < (1LL<<st->pts_wrap_bits) - av_rescale(60, st->time_base.den, st->time_base.num)) ?
AV_PTS_WRAP_ADD_OFFSET : AV_PTS_WRAP_SUB_OFFSET;

AVProgram *first_program = av_find_program_from_stream(s, NULL, stream_index);

if (!first_program) {
int default_stream_index = av_find_default_stream_index(s);
if (s->streams[default_stream_index]->pts_wrap_reference == AV_NOPTS_VALUE) {
for (i=0; i<s->nb_streams; i++) {
s->streams[i]->pts_wrap_reference = pts_wrap_reference;
s->streams[i]->pts_wrap_behavior = pts_wrap_behavior;
}
}
else {
st->pts_wrap_reference = s->streams[default_stream_index]->pts_wrap_reference;
st->pts_wrap_behavior = s->streams[default_stream_index]->pts_wrap_behavior;
}
}
else {
AVProgram *program = first_program;
while (program) {
if (program->pts_wrap_reference != AV_NOPTS_VALUE) {
pts_wrap_reference = program->pts_wrap_reference;
pts_wrap_behavior = program->pts_wrap_behavior;
break;
}
program = av_find_program_from_stream(s, program, stream_index);
}

// update every program with differing pts_wrap_reference
program = first_program;
while(program) {
if (program->pts_wrap_reference != pts_wrap_reference) {
for (i=0; i<program->nb_stream_indexes; i++) {
s->streams[program->stream_index[i]]->pts_wrap_reference = pts_wrap_reference;
s->streams[program->stream_index[i]]->pts_wrap_behavior = pts_wrap_behavior;
}

program->pts_wrap_reference = pts_wrap_reference;
program->pts_wrap_behavior = pts_wrap_behavior;
}
program = av_find_program_from_stream(s, program, stream_index);
}
}
return 1;
}
return 0;
}

static void update_initial_timestamps(AVFormatContext *s, int stream_index,
int64_t dts, int64_t pts)
int64_t dts, int64_t pts, AVPacket *pkt)
{
AVStream *st= s->streams[stream_index];
AVPacketList *pktl= s->packet_buffer;
Expand All @@ -973,6 +1055,16 @@ static void update_initial_timestamps(AVFormatContext *s, int stream_index,
if(st->start_time == AV_NOPTS_VALUE && pktl->pkt.pts != AV_NOPTS_VALUE)
st->start_time= pktl->pkt.pts;
}

if (update_wrap_reference(s, st, stream_index) && st->pts_wrap_behavior == AV_PTS_WRAP_SUB_OFFSET) {
// correct first time stamps to negative values
st->first_dts = wrap_timestamp(st, st->first_dts);
st->cur_dts = wrap_timestamp(st, st->cur_dts);
pkt->dts = wrap_timestamp(st, pkt->dts);
pkt->pts = wrap_timestamp(st, pkt->pts);
pts = wrap_timestamp(st, pts);
}

if (st->start_time == AV_NOPTS_VALUE)
st->start_time = pts;
}
Expand Down Expand Up @@ -1104,7 +1196,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
/* PTS = presentation timestamp */
if (pkt->dts == AV_NOPTS_VALUE)
pkt->dts = st->last_IP_pts;
update_initial_timestamps(s, pkt->stream_index, pkt->dts, pkt->pts);
update_initial_timestamps(s, pkt->stream_index, pkt->dts, pkt->pts, pkt);
if (pkt->dts == AV_NOPTS_VALUE)
pkt->dts = st->cur_dts;

Expand All @@ -1131,7 +1223,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
/* presentation is not delayed : PTS and DTS are the same */
if(pkt->pts == AV_NOPTS_VALUE)
pkt->pts = pkt->dts;
update_initial_timestamps(s, pkt->stream_index, pkt->pts, pkt->pts);
update_initial_timestamps(s, pkt->stream_index, pkt->pts, pkt->pts, pkt);
if(pkt->pts == AV_NOPTS_VALUE)
pkt->pts = st->cur_dts;
pkt->dts = pkt->pts;
Expand All @@ -1147,7 +1239,7 @@ static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
if(pkt->dts == AV_NOPTS_VALUE)
pkt->dts= st->pts_buffer[0];
if(st->codec->codec_id == CODEC_ID_H264){ // we skipped it above so we try here
update_initial_timestamps(s, pkt->stream_index, pkt->dts, pkt->pts); // this should happen on the first packet
update_initial_timestamps(s, pkt->stream_index, pkt->dts, pkt->pts, pkt); // this should happen on the first packet
}
if(pkt->dts > st->cur_dts)
st->cur_dts = pkt->dts;
Expand Down Expand Up @@ -1550,6 +1642,7 @@ int ff_add_index_entry(AVIndexEntry **index_entries,
int av_add_index_entry(AVStream *st,
int64_t pos, int64_t timestamp, int size, int distance, int flags)
{
timestamp = wrap_timestamp(st, timestamp);
return ff_add_index_entry(&st->index_entries, &st->nb_index_entries,
&st->index_entries_allocated_size, pos,
timestamp, size, distance, flags);
Expand Down Expand Up @@ -1602,6 +1695,12 @@ int av_seek_frame_binary(AVFormatContext *s, int stream_index, int64_t target_ts
}
#endif

static int64_t ff_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 ))
{
return wrap_timestamp(s->streams[stream_index], read_timestamp(s, stream_index, ppos, pos_limit));
}

int ff_seek_frame_binary(AVFormatContext *s, int stream_index, int64_t target_ts, int flags)
{
AVInputFormat *avif= s->iformat;
Expand Down Expand Up @@ -1689,7 +1788,7 @@ int64_t ff_gen_search(AVFormatContext *s, int stream_index, int64_t target_ts,

if(ts_min == AV_NOPTS_VALUE){
pos_min = s->data_offset;
ts_min = read_timestamp(s, stream_index, &pos_min, INT64_MAX);
ts_min = ff_read_timestamp(s, stream_index, &pos_min, INT64_MAX, read_timestamp);
if (ts_min == AV_NOPTS_VALUE)
return -1;
}
Expand All @@ -1705,15 +1804,15 @@ int64_t ff_gen_search(AVFormatContext *s, int stream_index, int64_t target_ts,
pos_max = filesize - 1;
do{
pos_max -= step;
ts_max = read_timestamp(s, stream_index, &pos_max, pos_max + step);
ts_max = ff_read_timestamp(s, stream_index, &pos_max, pos_max + step, read_timestamp);
step += step;
}while(ts_max == AV_NOPTS_VALUE && pos_max >= 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);
int64_t tmp_ts= ff_read_timestamp(s, stream_index, &tmp_pos, INT64_MAX, read_timestamp);
if(tmp_ts == AV_NOPTS_VALUE)
break;
ts_max= tmp_ts;
Expand Down Expand Up @@ -1760,7 +1859,7 @@ int64_t ff_gen_search(AVFormatContext *s, int stream_index, int64_t target_ts,
pos= pos_limit;
start_pos= pos;

ts = read_timestamp(s, stream_index, &pos, INT64_MAX); //may pass pos_limit instead of -1
ts = ff_read_timestamp(s, stream_index, &pos, INT64_MAX, read_timestamp); //may pass pos_limit instead of -1
if(pos == pos_max)
no_change++;
else
Expand Down Expand Up @@ -1788,9 +1887,9 @@ int64_t ff_gen_search(AVFormatContext *s, int stream_index, int64_t target_ts,
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);
ts_min = ff_read_timestamp(s, stream_index, &pos_min, INT64_MAX, read_timestamp);
pos_min++;
ts_max = read_timestamp(s, stream_index, &pos_min, INT64_MAX);
ts_max = ff_read_timestamp(s, stream_index, &pos_min, INT64_MAX, read_timestamp);
av_dlog(s, "pos=0x%"PRIx64" %"PRId64"<=%"PRId64"<=%"PRId64"\n",
pos, ts_min, target_ts, ts_max);
#endif
Expand Down Expand Up @@ -2992,6 +3091,8 @@ AVStream *avformat_new_stream(AVFormatContext *s, AVCodec *c)
st->cur_dts = 0;
st->first_dts = AV_NOPTS_VALUE;
st->probe_packets = MAX_PROBE_PACKETS;
st->pts_wrap_reference = AV_NOPTS_VALUE;
st->pts_wrap_behavior = AV_PTS_WRAP_IGNORE;

/* default pts setting is MPEG-like */
avpriv_set_pts_info(st, 33, 1, 90000);
Expand Down Expand Up @@ -3025,6 +3126,8 @@ AVProgram *av_new_program(AVFormatContext *ac, int id)
program->discard = AVDISCARD_NONE;
}
program->id = id;
program->pts_wrap_reference = AV_NOPTS_VALUE;
program->pts_wrap_behavior = AV_PTS_WRAP_IGNORE;

return program;
}
Expand Down

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