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Write the Seek Head element

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Originally committed as revision 10316 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
David Conrad 2007-09-05 00:23:19 +00:00
parent 801edb42d1
commit 967d815ae5
1 changed files with 139 additions and 1 deletions
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140
libavformat/matroskaenc.c
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@ -24,12 +24,29 @@
#include "xiph.h"
#include "matroska.h"
typedef struct mkv_seekhead_entry {
unsigned int elementid;
uint64_t segmentpos;
} mkv_seekhead_entry;
typedef struct mkv_seekhead {
offset_t filepos;
offset_t segment_offset; // the file offset to the beginning of the segment
int reserved_size; // -1 if appending to file
int max_entries;
mkv_seekhead_entry *entries;
int num_entries;
} mkv_seekhead;
typedef struct MatroskaMuxContext {
offset_t segment;
offset_t segment_offset;
offset_t cluster;
uint64_t cluster_pts;
offset_t duration_offset;
uint64_t duration;
mkv_seekhead *main_seekhead;
mkv_seekhead *cluster_seekhead;
} MatroskaMuxContext;
static void put_ebml_id(ByteIOContext *pb, unsigned int id)
@ -43,6 +60,17 @@ static void put_ebml_id(ByteIOContext *pb, unsigned int id)
put_byte(pb, id);
}
static int ebml_id_size(unsigned int id)
{
if (id >= 0x3fffff)
return 4;
if (id >= 0x7fff)
return 3;
if (id >= 0xff)
return 2;
return 1;
}
// XXX: test this thoroughly and get rid of minbytes hack (currently needed to
// use up all of the space reserved in start_ebml_master)
static void put_ebml_size(ByteIOContext *pb, uint64_t size, int minbytes)
@ -128,6 +156,91 @@ static void end_ebml_master(ByteIOContext *pb, offset_t start)
url_fseek(pb, pos, SEEK_SET);
}
// initializes a mkv_seekhead element to be ready to index level 1 matroska elements
// if numelements is greater than 0, it reserves enough space for that many elements
// at the current file position and writes the seekhead there, otherwise the seekhead
// will be appended to the file when end_mkv_seekhead() is called
static mkv_seekhead * mkv_start_seekhead(ByteIOContext *pb, offset_t segment_offset, int numelements)
{
mkv_seekhead *new_seekhead = av_mallocz(sizeof(mkv_seekhead));
if (new_seekhead == NULL)
return NULL;
new_seekhead->segment_offset = segment_offset;
if (numelements > 0) {
new_seekhead->filepos = url_ftell(pb);
// 21 bytes max for a seek entry, 10 bytes max for the SeekHead ID and size,
// and 3 bytes to guarantee that an EBML void element will fit afterwards
// XXX: 28 bytes right now because begin_ebml_master() reserves more than necessary
new_seekhead->reserved_size = numelements * 28 + 13;
new_seekhead->max_entries = numelements;
put_ebml_void(pb, new_seekhead->reserved_size);
}
return new_seekhead;
}
static int mkv_add_seekhead_entry(mkv_seekhead *seekhead, unsigned int elementid, uint64_t filepos)
{
mkv_seekhead_entry *entries = seekhead->entries;
int new_entry = seekhead->num_entries;
// don't store more elements than we reserved space for
if (seekhead->max_entries > 0 && seekhead->max_entries <= seekhead->num_entries)
return -1;
entries = av_realloc(entries, (seekhead->num_entries + 1) * sizeof(mkv_seekhead_entry));
if (entries == NULL)
return -1;
entries[new_entry].elementid = elementid;
entries[new_entry].segmentpos = filepos - seekhead->segment_offset;
seekhead->entries = entries;
seekhead->num_entries++;
return 0;
}
// returns the file offset where the seekhead was written and frees the seekhead
static offset_t mkv_write_seekhead(ByteIOContext *pb, mkv_seekhead *seekhead)
{
offset_t metaseek, seekentry, currentpos;
int i;
currentpos = url_ftell(pb);
if (seekhead->reserved_size > 0)
url_fseek(pb, seekhead->filepos, SEEK_SET);
metaseek = start_ebml_master(pb, MATROSKA_ID_SEEKHEAD);
for (i = 0; i < seekhead->num_entries; i++) {
mkv_seekhead_entry *entry = &seekhead->entries[i];
seekentry = start_ebml_master(pb, MATROSKA_ID_SEEKENTRY);
put_ebml_id(pb, MATROSKA_ID_SEEKID);
put_ebml_size(pb, ebml_id_size(entry->elementid), 0);
put_ebml_id(pb, entry->elementid);
put_ebml_uint(pb, MATROSKA_ID_SEEKPOSITION, entry->segmentpos);
end_ebml_master(pb, seekentry);
}
end_ebml_master(pb, metaseek);
if (seekhead->reserved_size > 0) {
uint64_t remaining = seekhead->filepos + seekhead->reserved_size - url_ftell(pb);
put_ebml_void(pb, remaining);
url_fseek(pb, currentpos, SEEK_SET);
currentpos = seekhead->filepos;
}
av_free(seekhead->entries);
av_free(seekhead);
return currentpos;
}
static int put_xiph_codecpriv(ByteIOContext *pb, AVCodecContext *codec)
{
offset_t codecprivate;
@ -168,6 +281,9 @@ static int mkv_write_tracks(AVFormatContext *s)
offset_t tracks;
int i, j;
if (mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_TRACKS, url_ftell(pb)) < 0)
return -1;
tracks = start_ebml_master(pb, MATROSKA_ID_TRACKS);
for (i = 0; i < s->nb_streams; i++) {
AVStream *st = s->streams[i];
@ -267,6 +383,17 @@ static int mkv_write_header(AVFormatContext *s)
end_ebml_master(pb, ebml_header);
mkv->segment = start_ebml_master(pb, MATROSKA_ID_SEGMENT);
mkv->segment_offset = url_ftell(pb);
// we write 2 seek heads - one at the end of the file to point to each cluster, and
// one at the beginning to point to all other level one elements (including the seek
// head at the end of the file), which isn't more than 10 elements if we only write one
// of each other currently defined level 1 element
mkv->main_seekhead = mkv_start_seekhead(pb, mkv->segment_offset, 10);
mkv->cluster_seekhead = mkv_start_seekhead(pb, mkv->segment_offset, 0);
if (mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_INFO, url_ftell(pb)) < 0)
return -1;
segment_info = start_ebml_master(pb, MATROSKA_ID_INFO);
put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, 1000000);
@ -287,6 +414,9 @@ static int mkv_write_header(AVFormatContext *s)
if (mkv_write_tracks(s) < 0)
return -1;
if (mkv_add_seekhead_entry(mkv->cluster_seekhead, MATROSKA_ID_CLUSTER, url_ftell(pb)) < 0)
return -1;
mkv->cluster = start_ebml_master(pb, MATROSKA_ID_CLUSTER);
put_ebml_uint(pb, MATROSKA_ID_CLUSTERTIMECODE, 0);
mkv->cluster_pts = 0;
@ -303,6 +433,10 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
// start a new cluster every 5 MB or 5 sec
if (url_ftell(pb) > mkv->cluster + 5*1024*1024 || pkt->pts > mkv->cluster_pts + 5000) {
end_ebml_master(pb, mkv->cluster);
if (mkv_add_seekhead_entry(mkv->cluster_seekhead, MATROSKA_ID_CLUSTER, url_ftell(pb)) < 0)
return -1;
mkv->cluster = start_ebml_master(pb, MATROSKA_ID_CLUSTER);
put_ebml_uint(pb, MATROSKA_ID_CLUSTERTIMECODE, pkt->pts);
mkv->cluster_pts = pkt->pts;
@ -323,10 +457,14 @@ static int mkv_write_trailer(AVFormatContext *s)
{
MatroskaMuxContext *mkv = s->priv_data;
ByteIOContext *pb = &s->pb;
offset_t currentpos;
offset_t currentpos, second_seekhead;
end_ebml_master(pb, mkv->cluster);
second_seekhead = mkv_write_seekhead(pb, mkv->cluster_seekhead);
mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_SEEKHEAD, second_seekhead);
mkv_write_seekhead(pb, mkv->main_seekhead);
// update the duration
currentpos = url_ftell(pb);
url_fseek(pb, mkv->duration_offset, SEEK_SET);