Commit 84c6aaf4 authored by Mark Nauwelaerts's avatar Mark Nauwelaerts

matroskademux: improve and simplify searching for cluster and position

... avoiding inefficiency proportional to file size
parent d7b736fa
......@@ -1654,7 +1654,8 @@ gst_matroska_cluster_compare (gint64 * i1, gint64 * i2)
/* searches for a cluster start from @pos,
* return GST_FLOW_OK and cluster position in @pos if found */
static GstFlowReturn
gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos,
gboolean forward)
{
gint64 newpos = *pos;
gint64 orig_offset;
......@@ -1671,8 +1672,8 @@ gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
orig_offset = demux->common.offset;
GST_LOG_OBJECT (demux, "searching cluster following offset %" G_GINT64_FORMAT,
*pos);
GST_LOG_OBJECT (demux, "searching cluster %s offset %" G_GINT64_FORMAT,
forward ? "following" : "preceding", *pos);
if (demux->clusters) {
gint64 *cpos;
......@@ -1680,7 +1681,7 @@ gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
cpos = gst_util_array_binary_search (demux->clusters->data,
demux->clusters->len, sizeof (gint64),
(GCompareDataFunc) gst_matroska_cluster_compare,
GST_SEARCH_MODE_AFTER, pos, NULL);
forward ? GST_SEARCH_MODE_AFTER : GST_SEARCH_MODE_BEFORE, pos, NULL);
/* sanity check */
if (cpos) {
GST_DEBUG_OBJECT (demux,
......@@ -1701,6 +1702,8 @@ gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
GstByteReader reader;
gint cluster_pos;
if (!forward)
newpos = MAX (0, newpos - chunk);
if (buf != NULL) {
gst_buffer_unmap (buf, &map);
gst_buffer_unref (buf);
......@@ -1725,16 +1728,25 @@ gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
}
gst_byte_reader_init (&reader, data, size);
resume:
cluster_pos = gst_byte_reader_masked_scan_uint32 (&reader, 0xffffffff,
GST_MATROSKA_ID_CLUSTER, 0, gst_byte_reader_get_remaining (&reader));
cluster_pos = -1;
while (1) {
gint found = gst_byte_reader_masked_scan_uint32 (&reader, 0xffffffff,
GST_MATROSKA_ID_CLUSTER, 0, gst_byte_reader_get_remaining (&reader));
if (forward) {
cluster_pos = found;
break;
}
/* need last occurrence when searching backwards */
if (found >= 0) {
cluster_pos = gst_byte_reader_get_pos (&reader) + found;
gst_byte_reader_skip (&reader, found + 4);
} else {
break;
}
}
if (cluster_pos >= 0) {
newpos += cluster_pos;
/* prepare resuming at next byte */
if (!gst_byte_reader_skip (&reader, cluster_pos + 1)) {
GST_DEBUG_OBJECT (demux, "Need more data -> continue");
continue;
}
GST_DEBUG_OBJECT (demux,
"found cluster ebml id at offset %" G_GINT64_FORMAT, newpos);
/* extra checks whether we really sync'ed to a cluster:
......@@ -1752,7 +1764,7 @@ gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
GST_ELEMENT_CAST (demux), &id, &length, &needed);
if (ret != GST_FLOW_OK) {
GST_DEBUG_OBJECT (demux, "need more data -> continue");
continue;
goto next;
}
g_assert (id == GST_MATROSKA_ID_CLUSTER);
GST_DEBUG_OBJECT (demux, "cluster size %" G_GUINT64_FORMAT ", prefix %d",
......@@ -1766,26 +1778,19 @@ gst_matroska_demux_search_cluster (GstMatroskaDemux * demux, gint64 * pos)
demux->common.offset += length + needed;
ret = gst_matroska_read_common_peek_id_length_pull (&demux->common,
GST_ELEMENT_CAST (demux), &id, &length, &needed);
if (ret != GST_FLOW_OK) {
/* we skipped one byte in the reader above, need to accomodate for
* that when resuming skipping from the reader instead of reading a
* new chunk */
newpos += 1;
goto resume;
}
if (ret != GST_FLOW_OK)
goto next;
GST_DEBUG_OBJECT (demux, "next element is %scluster",
id == GST_MATROSKA_ID_CLUSTER ? "" : "not ");
if (id == GST_MATROSKA_ID_CLUSTER)
break;
/* not ok, resume
* we skipped one byte in the reader above, need to accomodate for
* that when resuming skipping from the reader instead of reading a
* new chunk */
newpos += 1;
goto resume;
next:
if (forward)
newpos += 1;
} else {
/* partial cluster id may have been in tail of buffer */
newpos += MAX (gst_byte_reader_get_remaining (&reader), 4) - 3;
newpos +=
forward ? MAX (gst_byte_reader_get_remaining (&reader), 4) - 3 : 3;
}
}
......@@ -1809,20 +1814,18 @@ gst_matroska_demux_search_pos (GstMatroskaDemux * demux, GstClockTime time)
GstMatroskaIndex *entry = NULL;
GstMatroskaReadState current_state;
GstClockTime otime, prev_cluster_time, current_cluster_time, cluster_time;
gint64 opos, newpos, startpos = 0, current_offset;
GstClockTime atime;
gint64 opos, newpos, current_offset;
gint64 prev_cluster_offset = -1, current_cluster_offset, cluster_offset;
gint64 apos, maxpos;
guint64 cluster_size = 0;
const guint chunk = 64 * 1024;
GstFlowReturn ret;
guint64 length;
guint32 id;
guint needed;
/* (under)estimate new position, resync using cluster ebml id,
* and scan forward to appropriate cluster
* (and re-estimate if need to go backward) */
prev_cluster_time = GST_CLOCK_TIME_NONE;
/* estimate new position, resync using cluster ebml id,
* and bisect further or scan forward to appropriate cluster */
/* store some current state */
current_state = demux->common.state;
......@@ -1836,73 +1839,75 @@ gst_matroska_demux_search_pos (GstMatroskaDemux * demux, GstClockTime time)
/* estimate using start and current position */
GST_OBJECT_LOCK (demux);
opos = demux->common.offset - demux->common.ebml_segment_start;
apos = demux->first_cluster_offset;
atime = demux->stream_start_time;
opos = demux->common.offset;
otime = demux->common.segment.position;
GST_OBJECT_UNLOCK (demux);
/* sanitize */
time = MAX (time, demux->stream_start_time);
time = MAX (time, atime);
otime = MAX (otime, atime);
opos = MAX (opos, apos);
maxpos = gst_matroska_read_common_get_length (&demux->common);
/* avoid division by zero in first estimation below */
if (otime <= demux->stream_start_time)
otime = time;
/* invariants;
* apos <= opos
* atime <= otime
* apos always refer to a cluster before target time;
* opos may or may not be after target time, but if it is once so,
* then also in next iteration
* */
retry:
GST_LOG_OBJECT (demux,
"apos: %" G_GUINT64_FORMAT ", atime: %" GST_TIME_FORMAT ", %"
GST_TIME_FORMAT " in stream time, "
"opos: %" G_GUINT64_FORMAT ", otime: %" GST_TIME_FORMAT ", %"
GST_TIME_FORMAT " in stream time (start %" GST_TIME_FORMAT "), time %"
GST_TIME_FORMAT, opos, GST_TIME_ARGS (otime),
GST_TIME_ARGS (otime - demux->stream_start_time),
GST_TIME_FORMAT, apos, GST_TIME_ARGS (atime),
GST_TIME_ARGS (atime - demux->stream_start_time), opos,
GST_TIME_ARGS (otime), GST_TIME_ARGS (otime - demux->stream_start_time),
GST_TIME_ARGS (demux->stream_start_time), GST_TIME_ARGS (time));
if (otime <= demux->stream_start_time) {
newpos = 0;
g_assert (atime <= otime);
g_assert (apos <= opos);
if (time == GST_CLOCK_TIME_NONE) {
GST_DEBUG_OBJECT (demux, "searching last cluster");
newpos = maxpos;
if (newpos == -1) {
GST_DEBUG_OBJECT (demux, "unknown file size; bailing out");
goto exit;
}
} else if (otime <= atime) {
newpos = apos;
} else {
newpos =
gst_util_uint64_scale (opos - demux->common.ebml_segment_start,
time - demux->stream_start_time,
otime - demux->stream_start_time) - chunk;
if (newpos < 0)
newpos = 0;
newpos = apos +
gst_util_uint64_scale (opos - apos, time - atime, otime - atime);
if (maxpos != -1 && newpos > maxpos)
newpos = maxpos;
}
/* favour undershoot */
newpos = newpos * 90 / 100;
newpos += demux->common.ebml_segment_start;
GST_DEBUG_OBJECT (demux,
"estimated offset for %" GST_TIME_FORMAT ": %" G_GINT64_FORMAT,
GST_TIME_ARGS (time), newpos);
/* and at least start scanning before previous scan start to avoid looping */
startpos = startpos * 90 / 100;
if (startpos && startpos < newpos)
newpos = startpos;
/* read in at newpos and scan for ebml cluster id */
startpos = newpos;
while (1) {
ret = gst_matroska_demux_search_cluster (demux, &newpos);
if (ret == GST_FLOW_EOS) {
/* heuristic HACK */
newpos = startpos * 80 / 100;
GST_DEBUG_OBJECT (demux, "EOS; "
"new estimated offset for %" GST_TIME_FORMAT ": %" G_GINT64_FORMAT,
GST_TIME_ARGS (time), newpos);
startpos = newpos;
continue;
} else if (ret != GST_FLOW_OK) {
/* search backwards */
if (newpos > apos) {
ret = gst_matroska_demux_search_cluster (demux, &newpos, FALSE);
if (ret != GST_FLOW_OK)
goto exit;
} else {
break;
}
}
/* then start scanning and parsing for cluster time,
* re-estimate if overshoot, otherwise next cluster and so on */
* re-estimate if possible, otherwise next cluster and so on */
/* note that each re-estimate is entered with a change in apos or opos,
* avoiding infinite loop */
demux->common.offset = newpos;
demux->cluster_time = cluster_time = GST_CLOCK_TIME_NONE;
cluster_size = 0;
prev_cluster_time = GST_CLOCK_TIME_NONE;
while (1) {
/* peek and parse some elements */
ret = gst_matroska_read_common_peek_id_length_pull (&demux->common,
......@@ -1930,6 +1935,12 @@ retry:
GST_DEBUG_OBJECT (demux, "found cluster at offset %" G_GINT64_FORMAT
" with time %" GST_TIME_FORMAT, cluster_offset,
GST_TIME_ARGS (cluster_time));
if (time == GST_CLOCK_TIME_NONE) {
GST_DEBUG_OBJECT (demux, "found last cluster");
prev_cluster_time = cluster_time;
prev_cluster_offset = cluster_offset;
break;
}
if (cluster_time > time) {
GST_DEBUG_OBJECT (demux, "overshot target");
/* cluster overshoots */
......@@ -1950,6 +1961,30 @@ retry:
goto retry;
}
} else {
/* cluster undershoots */
GST_DEBUG_OBJECT (demux, "undershot target");
/* ok if close enough */
if (GST_CLOCK_DIFF (cluster_time, time) < 5 * GST_SECOND) {
GST_DEBUG_OBJECT (demux, "target close enough");
prev_cluster_time = cluster_time;
prev_cluster_offset = cluster_offset;
break;
}
if (otime > time) {
/* we are in between atime and otime => can bisect if worthwhile */
if (prev_cluster_time != GST_CLOCK_TIME_NONE &&
cluster_time > prev_cluster_time &&
(GST_CLOCK_DIFF (prev_cluster_time, cluster_time) * 10 <
GST_CLOCK_DIFF (cluster_time, time))) {
/* we moved at least one cluster forward,
* and it looks like target is still far away,
* let's estimate again */
GST_DEBUG_OBJECT (demux, "bisecting with new apos");
apos = cluster_offset;
atime = cluster_time;
goto retry;
}
}
/* cluster undershoots, goto next one */
prev_cluster_time = cluster_time;
prev_cluster_offset = cluster_offset;
......@@ -4176,7 +4211,8 @@ gst_matroska_demux_check_parse_error (GstMatroskaDemux * demux)
* search for cluster mark following current pos */
pos = demux->common.offset;
GST_WARNING_OBJECT (demux, "parse error, looking for next cluster");
if ((ret = gst_matroska_demux_search_cluster (demux, &pos)) != GST_FLOW_OK) {
if ((ret = gst_matroska_demux_search_cluster (demux, &pos, TRUE)) !=
GST_FLOW_OK) {
/* did not work, give up */
return ret;
} else {
......
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