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From Martin Kaiser via https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6984 : 

The attached patch extends the mpeg2 ts format detection to take into account
that trailing bytes might be added to each packet.

Once it finds no sync after 188 bytes, it checks an additional 40 bytes for the
next sync byte and adjusts the packet size accordingly.

Only the 188 bytes of the actual ts packet are passed on to wiretap, the
trailer is omitted.

svn path=/trunk/; revision=41863
This commit is contained in:
Jeff Morriss 2012-03-30 23:19:49 +00:00
parent 05113c3737
commit a572670849
1 changed files with 64 additions and 16 deletions
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80
wiretap/mp2t.c
View File

@ -49,9 +49,19 @@
#define MP2T_QAM256_BITRATE 38810700 /* bits per second */
#define MP2T_QAM64_BITRATE 26970350 /* bits per second */
/* we try to detect trailing data up to 40 bytes after each packet */
#define TRAILER_LEN_MAX 40
/* number of consecutive packets we must read to decide that a file
is actually an mpeg2 ts */
#define SYNC_STEPS 10
typedef struct {
guint32 offset;
struct wtap_nstime now;
/* length of trailing data (e.g. FEC) that's appended after each packet */
guint8 trailer_len;
} mp2t_filetype_t;
static gboolean
@ -81,6 +91,7 @@ mp2t_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
mp2t = (mp2t_filetype_t*) wth->priv;
*data_offset = mp2t->offset;
/* read only the actual mpeg2 ts packet, not including a trailer */
buffer_assure_space(wth->frame_buffer, MP2T_SIZE);
if (FALSE == mp2t_read_data(buffer_start_ptr(wth->frame_buffer),
MP2T_SIZE, err, err_info, wth->fh))
@ -88,12 +99,19 @@ mp2t_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
return FALSE;
}
mp2t->offset += MP2T_SIZE;
/* if there's a trailer, skip it and go to the start of the next packet */
if (mp2t->trailer_len!=0 &&
(-1 == file_seek(wth->fh, mp2t->trailer_len, SEEK_CUR, err))) {
return FALSE;
}
mp2t->offset += MP2T_SIZE + mp2t->trailer_len;
/* XXX - relative, not absolute, time stamps */
wth->phdr.presence_flags = WTAP_HAS_TS;
/* It would be really cool to be able to configure the bitrate... */
tmp = MP2T_SIZE * 8;
tmp = (MP2T_SIZE+mp2t->trailer_len) * 8;
tmp *= 1000000000;
tmp /= MP2T_QAM256_BITRATE;
@ -126,15 +144,18 @@ int
mp2t_open(wtap *wth, int *err, gchar **err_info)
{
int bytes_read;
guint8 buffer[MP2T_SIZE];
guint8 buffer[MP2T_SIZE+TRAILER_LEN_MAX];
guint8 trailer_len = 0;
guint sync_steps = 0;
int i;
int first;
mp2t_filetype_t *mp2t;
errno = WTAP_ERR_CANT_READ;
bytes_read = file_read(buffer, sizeof(buffer), wth->fh);
if (sizeof(buffer) != bytes_read) {
errno = WTAP_ERR_CANT_READ;
bytes_read = file_read(buffer, MP2T_SIZE, wth->fh);
if (MP2T_SIZE != bytes_read) {
*err = file_error(wth->fh, err_info);
return (*err == 0) ? 0 : -1;
}
@ -146,24 +167,50 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
break;
}
}
if (-1 == first) {
return 0;
return 0; /* wrong file type - not an mpeg2 ts file */
}
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return -1;
}
/* read the first 10 packets and make sure they all start with a sync byte */
for (i = 0; i < 10; i++) {
bytes_read = file_read(buffer, sizeof(buffer), wth->fh);
/* read some packets and make sure they all start with a sync byte */
do {
bytes_read = file_read(buffer, MP2T_SIZE+trailer_len, wth->fh);
if (bytes_read < 0)
return -1; /* read error */
if (bytes_read < (int)sizeof(buffer))
break; /* file has < 10 packets, that's ok if we're still in sync */
if (buffer[0] != MP2T_SYNC_BYTE)
return 0; /* not a valid mpeg2 ts */
}
if (bytes_read < MP2T_SIZE+trailer_len)
break; /* end of file, that's ok if we're still in sync */
if (buffer[0] == MP2T_SYNC_BYTE) {
sync_steps++;
}
else {
/* no sync byte found, check if trailing data is appended
and we have to increase the packet size */
/* if we've already detected a trailer field, we must remain in sync
another mismatch means we have no mpeg2 ts file */
if (trailer_len>0)
return 0;
/* check if a trailer is appended to the packet */
for (i=0; i<TRAILER_LEN_MAX; i++) {
if (buffer[i] == MP2T_SYNC_BYTE) {
trailer_len = i;
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return -1;
}
sync_steps = 0;
break;
}
}
/* no sync byte found in the vicinity, this is no mpeg2 ts file */
if (i==TRAILER_LEN_MAX)
return 0;
}
} while (sync_steps < SYNC_STEPS);
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return -1;
}
@ -184,6 +231,7 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
mp2t->offset = (guint32) first;
mp2t->now.secs = 0;
mp2t->now.nsecs = 0;
mp2t->trailer_len = trailer_len;
return 1;
}