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avformat/matroskaenc: Rename functions to better reflect what they do 

EBML uses variable length integers both for the EBML IDs as well as for
the EBML lengths; Matroska also uses them for the TrackNumber in
(Simple)Blocks and for the lengths of laces when EBML lacing is used.

When encoding EBML lengths, certain encodings have a special meaning,
namely that the element has an unknown length. This is not so when
encoding general EBML variable length integers.

Yet the functions called ebml_num_size() and put_ebml_num() had this
special meaning hardcoded, i.e. they are there to write EBML lengths and
not general EBML numbers. So rename them.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-04-15 03:39:37 +02:00
parent 9b0f9003df
commit 40d038a635
1 changed files with 27 additions and 26 deletions
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53
libavformat/matroskaenc.c
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@ -190,30 +190,31 @@ static void put_ebml_size_unknown(AVIOContext *pb, int bytes)
}
/**
* Calculate how many bytes are needed to represent a given number in EBML.
* Calculate how many bytes are needed to represent the length field
* of an EBML element whose payload has a given length.
*/
static int ebml_num_size(uint64_t num)
static int ebml_length_size(uint64_t length)
{
int bytes = 0;
num++;
length++;
do {
bytes++;
} while (num >>= 7);
} while (length >>= 7);
return bytes;
}
/**
* Write a number in EBML variable length format.
* Write a length as EBML variable length integer.
*
* @param bytes The number of bytes that need to be used to write the number.
* If zero, the minimal number of bytes will be used.
*/
static void put_ebml_num(AVIOContext *pb, uint64_t num, int bytes)
static void put_ebml_length(AVIOContext *pb, uint64_t length, int bytes)
{
int i, needed_bytes = ebml_num_size(num);
int i, needed_bytes = ebml_length_size(length);
// sizes larger than this are currently undefined in EBML
av_assert0(num < (1ULL << 56) - 1);
av_assert0(length < (1ULL << 56) - 1);
if (bytes == 0)
bytes = needed_bytes;
@ -221,9 +222,9 @@ static void put_ebml_num(AVIOContext *pb, uint64_t num, int bytes)
// the bytes that we ought to use.
av_assert0(bytes >= needed_bytes);
num |= 1ULL << bytes * 7;
length |= 1ULL << bytes * 7;
for (i = bytes - 1; i >= 0; i--)
avio_w8(pb, (uint8_t)(num >> i * 8));
avio_w8(pb, (uint8_t)(length >> i * 8));
}
/**
@ -232,7 +233,7 @@ static void put_ebml_num(AVIOContext *pb, uint64_t num, int bytes)
static void put_ebml_uid(AVIOContext *pb, uint32_t elementid, uint64_t uid)
{
put_ebml_id(pb, elementid);
put_ebml_num(pb, 8, 0);
put_ebml_length(pb, 8, 0);
avio_wb64(pb, uid);
}
@ -244,7 +245,7 @@ static void put_ebml_uint(AVIOContext *pb, uint32_t elementid, uint64_t val)
bytes++;
put_ebml_id(pb, elementid);
put_ebml_num(pb, bytes, 0);
put_ebml_length(pb, bytes, 0);
for (i = bytes - 1; i >= 0; i--)
avio_w8(pb, (uint8_t)(val >> i * 8));
}
@ -257,7 +258,7 @@ static void put_ebml_sint(AVIOContext *pb, uint32_t elementid, int64_t val)
while (tmp>>=8) bytes++;
put_ebml_id(pb, elementid);
put_ebml_num(pb, bytes, 0);
put_ebml_length(pb, bytes, 0);
for (i = bytes - 1; i >= 0; i--)
avio_w8(pb, (uint8_t)(val >> i * 8));
}
@ -265,7 +266,7 @@ static void put_ebml_sint(AVIOContext *pb, uint32_t elementid, int64_t val)
static void put_ebml_float(AVIOContext *pb, uint32_t elementid, double val)
{
put_ebml_id(pb, elementid);
put_ebml_num(pb, 8, 0);
put_ebml_length(pb, 8, 0);
avio_wb64(pb, av_double2int(val));
}
@ -273,7 +274,7 @@ static void put_ebml_binary(AVIOContext *pb, uint32_t elementid,
const void *buf, int size)
{
put_ebml_id(pb, elementid);
put_ebml_num(pb, size, 0);
put_ebml_length(pb, size, 0);
avio_write(pb, buf, size);
}
@ -299,10 +300,10 @@ static void put_ebml_void(AVIOContext *pb, int size)
// size if possible, 1 byte otherwise
if (size < 10) {
size -= 2;
put_ebml_num(pb, size, 0);
put_ebml_length(pb, size, 0);
} else {
size -= 9;
put_ebml_num(pb, size, 8);
put_ebml_length(pb, size, 8);
}
ffio_fill(pb, 0, size);
}
@ -310,7 +311,7 @@ static void put_ebml_void(AVIOContext *pb, int size)
static ebml_master start_ebml_master(AVIOContext *pb, uint32_t elementid,
uint64_t expectedsize)
{
int bytes = expectedsize ? ebml_num_size(expectedsize) : 8;
int bytes = expectedsize ? ebml_length_size(expectedsize) : 8;
put_ebml_id(pb, elementid);
put_ebml_size_unknown(pb, bytes);
@ -323,7 +324,7 @@ static void end_ebml_master(AVIOContext *pb, ebml_master master)
if (avio_seek(pb, master.pos - master.sizebytes, SEEK_SET) < 0)
return;
put_ebml_num(pb, pos - master.pos, master.sizebytes);
put_ebml_length(pb, pos - master.pos, master.sizebytes);
avio_seek(pb, pos, SEEK_SET);
}
@ -349,7 +350,7 @@ static void end_ebml_master_crc32(AVIOContext *pb, AVIOContext **dyn_cp,
put_ebml_id(pb, id);
size = avio_get_dyn_buf(*dyn_cp, &buf);
put_ebml_num(pb, size, length_size);
put_ebml_length(pb, size, length_size);
if (mkv->write_crc) {
skip = 6; /* Skip reserved 6-byte long void element from the dynamic buffer. */
AV_WL32(crc, av_crc(av_crc_get_table(AV_CRC_32_IEEE_LE), UINT32_MAX, buf + skip, size - skip) ^ UINT32_MAX);
@ -376,7 +377,7 @@ static void end_ebml_master_crc32_preliminary(AVIOContext *pb, AVIOContext *dyn_
*pos = avio_tell(pb);
put_ebml_id(pb, id);
put_ebml_num(pb, size, 0);
put_ebml_length(pb, size, 0);
avio_write(pb, buf, size);
}
@ -461,7 +462,7 @@ static int mkv_write_seekhead(AVIOContext *pb, MatroskaMuxContext *mkv,
MAX_SEEKENTRY_SIZE);
put_ebml_id(dyn_cp, MATROSKA_ID_SEEKID);
put_ebml_num(dyn_cp, ebml_id_size(entry->elementid), 0);
put_ebml_length(dyn_cp, ebml_id_size(entry->elementid), 0);
put_ebml_id(dyn_cp, entry->elementid);
put_ebml_uint(dyn_cp, MATROSKA_ID_SEEKPOSITION, entry->segmentpos);
@ -1885,7 +1886,7 @@ static int mkv_write_header(AVFormatContext *s)
static int mkv_blockgroup_size(int pkt_size)
{
int size = pkt_size + 4;
size += ebml_num_size(size);
size += ebml_length_size(size);
size += 2; // EBML ID for block and block duration
size += 9; // max size of block duration incl. length field
return size;
@ -2024,7 +2025,7 @@ static int mkv_write_block(AVFormatContext *s, AVIOContext *pb,
}
put_ebml_id(pb, blockid);
put_ebml_num(pb, size + 4, 0);
put_ebml_length(pb, size + 4, 0);
// this assumes stream_index is less than 126
avio_w8(pb, 0x80 | track_number);
avio_wb16(pb, ts - mkv->cluster_pts);
@ -2092,7 +2093,7 @@ static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, AVPacket *p
blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP, mkv_blockgroup_size(size));
put_ebml_id(pb, MATROSKA_ID_BLOCK);
put_ebml_num(pb, size + 4, 0);
put_ebml_length(pb, size + 4, 0);
avio_w8(pb, 0x80 | track->track_num); // this assumes track_num is less than 126
avio_wb16(pb, ts - mkv->cluster_pts);
avio_w8(pb, flags);
@ -2437,7 +2438,7 @@ static int mkv_write_trailer(AVFormatContext *s)
if (mkv->reserve_cues_space) {
size = avio_tell(cues);
length_size = ebml_num_size(size);
length_size = ebml_length_size(size);
size += 4 + length_size;
if (mkv->reserve_cues_space < size) {
av_log(s, AV_LOG_WARNING,