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Code Issues Releases Activity

avformat/matroskaenc: Move adding SeekEntry into end_ebml_master_crc32()

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Up until now, SeekEntries were already added before
start_ebml_master_crc32() was even called and before we were actually
sure that we really write the element the SeekHead references: After
all, we might also error out later; and given that the allocations
implicit in dynamic buffers should be checked, end_ebml_master_crc32()
will eventually have to return errors itself, so that it is the right
place to add SeekHead entries.

The earlier behaviour is of course a remnant of the time in which
start_ebml_master_crc32() really did output something, so that the
position before start_ebml_master_crc32() needed to be recorded.
Erroring out later is also not as dangerous as it seems because in
this case no SeekHead will be written (if it happened when writing
the header, the whole muxing process would abort; if it happened
when writing the trailer (when writing chapters not available initially),
writing the trailer would be aborted and no SeekHead containing the
bogus chapter entry would be written).

This commit does not change the way the SeekEntries are added for those
elements that are output preliminarily; this is so because the SeekHead
is written before those elements are finally output and doing it
otherwise would increase the amount of seeks.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-04-27 04:34:45 +02:00
parent c801ab43c3
commit 4ed3c925c3
1 changed files with 33 additions and 31 deletions
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64
libavformat/matroskaenc.c
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@ -349,6 +349,17 @@ static void end_ebml_master(AVIOContext *pb, ebml_master master)
avio_seek(pb, pos, SEEK_SET);
}
static void mkv_add_seekhead_entry(MatroskaMuxContext *mkv, uint32_t elementid,
uint64_t filepos)
{
mkv_seekhead *seekhead = &mkv->seekhead;
av_assert1(seekhead->num_entries < MAX_SEEKHEAD_ENTRIES);
seekhead->entries[seekhead->num_entries].elementid = elementid;
seekhead->entries[seekhead->num_entries++].segmentpos = filepos - mkv->segment_offset;
}
static int start_ebml_master_crc32(AVIOContext **dyn_cp, MatroskaMuxContext *mkv)
{
int ret;
@ -364,11 +375,15 @@ static int start_ebml_master_crc32(AVIOContext **dyn_cp, MatroskaMuxContext *mkv
static void end_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp,
MatroskaMuxContext *mkv, uint32_t id,
int length_size, int keep_buffer)
int length_size, int keep_buffer,
int add_seekentry)
{
uint8_t *buf, crc[4];
int size, skip = 0;
if (add_seekentry)
mkv_add_seekhead_entry(mkv, id, avio_tell(pb));
put_ebml_id(pb, id);
size = avio_get_dyn_buf(*dyn_cp, &buf);
put_ebml_length(pb, size, length_size);
@ -441,17 +456,6 @@ static void mkv_start_seekhead(MatroskaMuxContext *mkv, AVIOContext *pb)
put_ebml_void(pb, mkv->seekhead.reserved_size);
}
static void mkv_add_seekhead_entry(MatroskaMuxContext *mkv, uint32_t elementid,
uint64_t filepos)
{
mkv_seekhead *seekhead = &mkv->seekhead;
av_assert1(seekhead->num_entries < MAX_SEEKHEAD_ENTRIES);
seekhead->entries[seekhead->num_entries].elementid = elementid;
seekhead->entries[seekhead->num_entries++].segmentpos = filepos - mkv->segment_offset;
}
/**
* Write the SeekHead to the file at the location reserved for it
* and seek to destpos afterwards. When error_on_seek_failure
@ -489,7 +493,7 @@ static int mkv_write_seekhead(AVIOContext *pb, MatroskaMuxContext *mkv,
put_ebml_uint(dyn_cp, MATROSKA_ID_SEEKPOSITION, entry->segmentpos);
end_ebml_master(dyn_cp, seekentry);
}
end_ebml_master_crc32(pb, &dyn_cp, mkv, MATROSKA_ID_SEEKHEAD, 0, 0);
end_ebml_master_crc32(pb, &dyn_cp, mkv, MATROSKA_ID_SEEKHEAD, 0, 0, 0);
remaining = seekhead->filepos + seekhead->reserved_size - avio_tell(pb);
put_ebml_void(pb, remaining);
@ -1421,7 +1425,8 @@ static int mkv_write_tracks(AVFormatContext *s)
end_ebml_master_crc32_preliminary(pb, mkv->tracks_bc,
MATROSKA_ID_TRACKS, &mkv->tracks_pos);
else
end_ebml_master_crc32(pb, &mkv->tracks_bc, mkv, MATROSKA_ID_TRACKS, 0, 0);
end_ebml_master_crc32(pb, &mkv->tracks_bc, mkv,
MATROSKA_ID_TRACKS, 0, 0, 0);
return 0;
}
@ -1443,8 +1448,6 @@ static int mkv_write_chapters(AVFormatContext *s)
break;
}
mkv_add_seekhead_entry(mkv, MATROSKA_ID_CHAPTERS, avio_tell(pb));
ret = start_ebml_master_crc32(&dyn_cp, mkv);
if (ret < 0)
return ret;
@ -1481,7 +1484,7 @@ static int mkv_write_chapters(AVFormatContext *s)
end_ebml_master(dyn_cp, chapteratom);
}
end_ebml_master(dyn_cp, editionentry);
end_ebml_master_crc32(pb, &dyn_cp, mkv, MATROSKA_ID_CHAPTERS, 0, 0);
end_ebml_master_crc32(pb, &dyn_cp, mkv, MATROSKA_ID_CHAPTERS, 0, 0, 1);
mkv->wrote_chapters = 1;
return 0;
@ -1682,7 +1685,8 @@ static int mkv_write_tags(AVFormatContext *s)
end_ebml_master_crc32_preliminary(s->pb, mkv->tags_bc,
MATROSKA_ID_TAGS, &mkv->tags_pos);
else
end_ebml_master_crc32(s->pb, &mkv->tags_bc, mkv, MATROSKA_ID_TAGS, 0, 0);
end_ebml_master_crc32(s->pb, &mkv->tags_bc, mkv,
MATROSKA_ID_TAGS, 0, 0, 0);
}
return 0;
}
@ -1713,8 +1717,6 @@ static int mkv_write_attachments(AVFormatContext *s)
if (!mkv->nb_attachments)
return 0;
mkv_add_seekhead_entry(mkv, MATROSKA_ID_ATTACHMENTS, avio_tell(pb));
ret = start_ebml_master_crc32(&dyn_cp, mkv);
if (ret < 0)
return ret;
@ -1746,7 +1748,7 @@ static int mkv_write_attachments(AVFormatContext *s)
put_ebml_uid(dyn_cp, MATROSKA_ID_FILEUID, track->uid);
end_ebml_master(dyn_cp, attached_file);
}
end_ebml_master_crc32(pb, &dyn_cp, mkv, MATROSKA_ID_ATTACHMENTS, 0, 0);
end_ebml_master_crc32(pb, &dyn_cp, mkv, MATROSKA_ID_ATTACHMENTS, 0, 0, 1);
return 0;
}
@ -1868,7 +1870,8 @@ static int mkv_write_header(AVFormatContext *s)
end_ebml_master_crc32_preliminary(s->pb, mkv->info_bc,
MATROSKA_ID_INFO, &mkv->info_pos);
else
end_ebml_master_crc32(s->pb, &mkv->info_bc, mkv, MATROSKA_ID_INFO, 0, 0);
end_ebml_master_crc32(s->pb, &mkv->info_bc, mkv,
MATROSKA_ID_INFO, 0, 0, 0);
pb = s->pb;
ret = mkv_write_tracks(s);
@ -2153,7 +2156,8 @@ static void mkv_end_cluster(AVFormatContext *s)
{
MatroskaMuxContext *mkv = s->priv_data;
end_ebml_master_crc32(s->pb, &mkv->cluster_bc, mkv, MATROSKA_ID_CLUSTER, 0, 1);
end_ebml_master_crc32(s->pb, &mkv->cluster_bc, mkv,
MATROSKA_ID_CLUSTER, 0, 1, 0);
if (!mkv->have_video) {
for (unsigned i = 0; i < s->nb_streams; i++)
mkv->tracks[i].has_cue = 0;
@ -2447,7 +2451,7 @@ static int mkv_write_trailer(AVFormatContext *s)
if (mkv->cluster_pos != -1) {
end_ebml_master_crc32(pb, &mkv->cluster_bc, mkv,
MATROSKA_ID_CLUSTER, 0, 0);
MATROSKA_ID_CLUSTER, 0, 0, 0);
}
ret = mkv_write_chapters(s);
@ -2463,7 +2467,6 @@ static int mkv_write_trailer(AVFormatContext *s)
if (mkv->cues.num_entries) {
AVIOContext *cues = NULL;
uint64_t size;
int64_t cuespos = endpos;
int length_size = 0;
ret = start_ebml_master_crc32(&cues, mkv);
@ -2490,7 +2493,6 @@ static int mkv_write_trailer(AVFormatContext *s)
ffio_free_dyn_buf(&cues);
goto after_cues;
} else {
cuespos = mkv->cues_pos;
if ((ret64 = avio_seek(pb, mkv->cues_pos, SEEK_SET)) < 0) {
ffio_free_dyn_buf(&cues);
return ret64;
@ -2506,9 +2508,8 @@ static int mkv_write_trailer(AVFormatContext *s)
}
}
}
mkv_add_seekhead_entry(mkv, MATROSKA_ID_CUES, cuespos);
end_ebml_master_crc32(pb, &cues, mkv, MATROSKA_ID_CUES,
length_size, 0);
length_size, 0, 1);
if (mkv->reserve_cues_space) {
if (size < mkv->reserve_cues_space)
put_ebml_void(pb, mkv->reserve_cues_space - size);
@ -2525,13 +2526,13 @@ static int mkv_write_trailer(AVFormatContext *s)
av_log(s, AV_LOG_DEBUG, "end duration = %" PRIu64 "\n", mkv->duration);
avio_seek(mkv->info_bc, mkv->duration_offset, SEEK_SET);
put_ebml_float(mkv->info_bc, MATROSKA_ID_DURATION, mkv->duration);
end_ebml_master_crc32(pb, &mkv->info_bc, mkv, MATROSKA_ID_INFO, 0, 0);
end_ebml_master_crc32(pb, &mkv->info_bc, mkv, MATROSKA_ID_INFO, 0, 0, 0);
if (mkv->tracks_bc) {
// write Tracks master
avio_seek(pb, mkv->tracks_pos, SEEK_SET);
end_ebml_master_crc32(pb, &mkv->tracks_bc, mkv,
MATROSKA_ID_TRACKS, 0, 0);
MATROSKA_ID_TRACKS, 0, 0, 0);
}
// update stream durations
@ -2559,7 +2560,8 @@ static int mkv_write_trailer(AVFormatContext *s)
}
avio_seek(pb, mkv->tags_pos, SEEK_SET);
end_ebml_master_crc32(pb, &mkv->tags_bc, mkv, MATROSKA_ID_TAGS, 0, 0);
end_ebml_master_crc32(pb, &mkv->tags_bc, mkv,
MATROSKA_ID_TAGS, 0, 0, 0);
}
avio_seek(pb, endpos, SEEK_SET);