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seeking stuff 

adaptively change middle position selection algo for seeking, this avoids some ugly worstcases of the interpolated variant
  avoid backward search for mpeg where possible, its 17 times slower then forward according to my benchmark

Originally committed as revision 2710 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2004-01-17 20:26:44 +00:00
parent 3e9245a98e
commit 0888ac4f27
2 changed files with 67 additions and 50 deletions
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30
libavformat/asf.c
View File

@ -1401,6 +1401,7 @@ static int asf_read_seek(AVFormatContext *s, int stream_index, int64_t pts)
AVStream *st;
int64_t pos;
int64_t pos_min, pos_max, pts_min, pts_max, cur_pts, pos_limit;
int no_change;
if (stream_index == -1)
stream_index= av_find_default_stream_index(s);
@ -1454,14 +1455,24 @@ static int asf_read_seek(AVFormatContext *s, int stream_index, int64_t pts)
pos_limit= pos_max;
}
no_change=0;
while (pos_min < pos_limit) {
int64_t start_pos;
assert(pos_limit <= pos_max);
// interpolate position (better than dichotomy)
pos = (int64_t)((double)(pos_limit - pos_min) *
(double)(pts - pts_min) /
(double)(pts_max - pts_min)) + pos_min;
if(no_change==0){
int64_t approximate_keyframe_distance= pos_max - pos_limit;
// interpolate position (better than dichotomy)
pos = (int64_t)((double)(pos_max - pos_min) *
(double)(pts - pts_min) /
(double)(pts_max - pts_min)) + pos_min - approximate_keyframe_distance;
}else if(no_change==1){
// bisection, if interpolation failed to change min or 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)
@ -1470,13 +1481,16 @@ static int asf_read_seek(AVFormatContext *s, int stream_index, int64_t pts)
// read the next timestamp
cur_pts = asf_read_pts(s, &pos, stream_index);
if(pos == pos_max)
no_change++;
else
no_change=0;
#ifdef DEBUG_SEEK
printf("%Ld %Ld %Ld / %Ld %Ld %Ld target:%Ld limit:%Ld start:%Ld\n", pos_min, pos, pos_max, pts_min, cur_pts, pts_max, pts, pos_limit, start_pos);
#endif
if (cur_pts == AV_NOPTS_VALUE) {
printf("NOPTS\n");
return -1;
} else if (pts < cur_pts) {
assert (cur_pts != AV_NOPTS_VALUE);
if (pts < cur_pts) {
pos_limit = start_pos - 1;
pos_max = pos;
pts_max = cur_pts;

87
libavformat/mpeg.c
View File

@ -1037,9 +1037,9 @@ static int64_t mpegps_read_dts(AVFormatContext *s, int stream_index,
static int mpegps_read_seek(AVFormatContext *s,
int stream_index, int64_t timestamp)
{
int64_t pos_min, pos_max, pos;
int64_t pos_min, pos_max, pos, pos_limit;
int64_t dts_min, dts_max, dts;
int index;
int index, no_change;
AVStream *st;
timestamp = (timestamp * 90000) / AV_TIME_BASE;
@ -1057,6 +1057,7 @@ static int mpegps_read_seek(AVFormatContext *s,
dts_max=
dts_min= AV_NOPTS_VALUE;
pos_limit= -1; //gcc falsely says it may be uninitalized
st= s->streams[stream_index];
if(st->index_entries){
@ -1080,6 +1081,7 @@ static int mpegps_read_seek(AVFormatContext *s,
assert(e->timestamp >= timestamp);
pos_max= e->pos;
dts_max= e->timestamp;
pos_limit= pos_max - e->min_distance;
#ifdef DEBUG_SEEK
printf("unsing cached pos_max=0x%llx dts_max=%0.3f\n",
pos_max,dts_max / 90000.0);
@ -1099,61 +1101,62 @@ static int mpegps_read_seek(AVFormatContext *s,
if(dts_max == AV_NOPTS_VALUE){
pos_max = url_filesize(url_fileno(&s->pb)) - 1;
dts_max = mpegps_read_dts(s, stream_index, &pos_max, 0);
pos_limit= pos_max;
}
while (pos_min <= pos_max) {
no_change=0;
while (pos_min < pos_limit) {
#ifdef DEBUG_SEEK
printf("pos_min=0x%llx pos_max=0x%llx dts_min=%0.3f dts_max=%0.3f\n",
pos_min, pos_max,
dts_min / 90000.0, dts_max / 90000.0);
#endif
if (timestamp <= dts_min) {
pos = pos_min;
goto found;
} else if (timestamp >= dts_max) {
pos = pos_max;
goto found;
} else {
/* interpolate position (better than dichotomy) */
pos = (int64_t)((double)(pos_max - pos_min) *
int64_t start_pos;
assert(pos_limit <= pos_max);
if(no_change==0){
int64_t approximate_keyframe_distance= pos_max - pos_limit;
// interpolate position (better than dichotomy)
pos = (int64_t)((double)(pos_max - pos_min) *
(double)(timestamp - dts_min) /
(double)(dts_max - dts_min)) + pos_min;
(double)(dts_max - dts_min)) + pos_min - approximate_keyframe_distance;
}else if(no_change==1){
// bisection, if interpolation failed to change min or 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 keframes 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;
// read the next timestamp
dts = mpegps_read_dts(s, stream_index, &pos, 1);
if(pos == pos_max)
no_change++;
else
no_change=0;
#ifdef DEBUG_SEEK
printf("pos=0x%llx\n", pos);
printf("%Ld %Ld %Ld / %Ld %Ld %Ld target:%Ld limit:%Ld start:%Ld noc:%d\n", pos_min, pos, pos_max, dts_min, dts, dts_max, timestamp, pos_limit, start_pos, no_change);
#endif
/* read the next timestamp */
dts = mpegps_read_dts(s, stream_index, &pos, 1);
/* check if we are lucky */
if (dts == AV_NOPTS_VALUE) {
/* should never happen */
pos = pos_min;
goto found;
} else if (timestamp == dts) {
goto found;
} else if (timestamp < dts) {
assert(dts != AV_NOPTS_VALUE);
if (timestamp < dts) {
pos_limit = start_pos - 1;
pos_max = pos;
dts_max = mpegps_read_dts(s, stream_index, &pos_max, 0);
if (dts_max == AV_NOPTS_VALUE) {
/* should never happen */
break;
} else if (timestamp >= dts_max) {
pos = pos_max;
goto found;
}
dts_max = dts;
} else {
pos_min = pos + 1;
dts_min = mpegps_read_dts(s, stream_index, &pos_min, 1);
if (dts_min == AV_NOPTS_VALUE) {
/* should never happen */
goto found;
} else if (timestamp <= dts_min) {
goto found;
}
pos_min = pos;
dts_min = dts;
/* check if we are lucky */
if (timestamp == dts)
break;
}
}
pos = pos_min;
found:
#ifdef DEBUG_SEEK
pos_min = pos;
dts_min = mpegps_read_dts(s, stream_index, &pos_min, 1);