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Add PCR based stream times for MPEG ts files. 

Change-Id: Ie1308829c3ad44d842bf12c7ebc5c200c942d8cc
Reviewed-on: https://code.wireshark.org/review/7750
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
This commit is contained in:
Weston Schmidt 2015-03-18 21:51:03 -07:00 committed by Martin Kaiser
parent f031fafdcc
commit 7253ee7611
1 changed files with 117 additions and 3 deletions
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120
wiretap/mp2t.c
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@ -42,8 +42,8 @@
#define MP2T_SYNC_BYTE 0x47
#define MP2T_SIZE 188
#define MP2T_QAM256_BITRATE 38810700 /* bits per second */
#define MP2T_QAM64_BITRATE 26970350 /* bits per second */
#define MP2T_PCR_CLOCK 27000000 /* cycles per second - 27MHz */
/* we try to detect trailing data up to 40 bytes after each packet */
#define TRAILER_LEN_MAX 40
@ -55,6 +55,7 @@
typedef struct {
int start_offset;
guint64 bitrate;
/* length of trailing data (e.g. FEC) that's appended after each packet */
guint8 trailer_len;
} mp2t_filetype_t;
@ -86,8 +87,8 @@ mp2t_read_packet(mp2t_filetype_t *mp2t, FILE_T fh, gint64 offset,
* It would be really cool to be able to configure the bitrate...
*/
tmp = ((guint64)(offset - mp2t->start_offset) * 8); /* offset, in bits */
phdr->ts.secs = (time_t)(tmp / MP2T_QAM256_BITRATE);
phdr->ts.nsecs = (int)((tmp % MP2T_QAM256_BITRATE) * 1000000000 / MP2T_QAM256_BITRATE);
phdr->ts.secs = (time_t)(tmp / mp2t->bitrate);
phdr->ts.nsecs = (int)((tmp % mp2t->bitrate) * 1000000000 / mp2t->bitrate);
phdr->caplen = MP2T_SIZE;
phdr->len = MP2T_SIZE;
@ -140,6 +141,104 @@ mp2t_seek_read(wtap *wth, gint64 seek_off, struct wtap_pkthdr *phdr,
return TRUE;
}
static guint64
mp2t_read_pcr(guint8 *buffer)
{
guint64 base;
guint64 ext;
base = pntoh40(buffer);
base >>= 7;
ext = pntoh16(&buffer[4]);
ext &= 0x01ff;
return (base * 300 + ext);
}
static gboolean
mp2t_find_next_pcr(wtap *wth, int *err, gchar **err_info, guint32 *index, guint64 *pcr, guint16 *pid)
{
guint8 buffer[MP2T_SIZE];
gboolean found;
guint8 afc;
found = FALSE;
while (FALSE == found) {
(*index)++;
if (!wtap_read_bytes(wth->fh, buffer, MP2T_SIZE, err, err_info)) {
return FALSE;
}
if (MP2T_SYNC_BYTE != buffer[0]) {
continue;
}
/* Read out the AFC value. */
afc = 3 & (buffer[3] >> 4);
if (afc < 2) {
continue;
}
/* Check the length. */
if (buffer[4] < 7) {
continue;
}
/* Check that there is the PCR flag. */
if (0x10 != (0x10 & buffer[5])) {
continue;
}
/* We have a PCR value! */
*pcr = mp2t_read_pcr(&buffer[6]);
*pid = 0x01ff & pntoh16(&buffer[1]);
found = TRUE;
}
return TRUE;
}
static guint64
mp2t_bits_per_second(wtap *wth, int *err, gchar **err_info)
{
guint32 pn1, pn2;
guint64 pcr1, pcr2;
guint16 pid1, pid2;
guint32 index;
guint64 pcr_delta, bits_passed;
/* Find the first PCR + PID.
* Then find another PCR in that PID.
* Take the difference and that's our bitrate.
* All the different PCRs in different PIDs 'should' be the same.
*/
index = 0;
if (FALSE == mp2t_find_next_pcr(wth, err, err_info, &index, &pcr1, &pid1)) {
return 0;
}
pn1 = index;
pn2 = pn1;
while (pn1 == pn2) {
if (FALSE == mp2t_find_next_pcr(wth, err, err_info, &index, &pcr2, &pid2)) {
return 0;
}
if (pid1 == pid2) {
pn2 = index;
}
}
pcr_delta = pcr2 - pcr1;
bits_passed = MP2T_SIZE * (pn2 - pn1) * 8;
return ((MP2T_PCR_CLOCK * bits_passed) / pcr_delta);
}
wtap_open_return_val
mp2t_open(wtap *wth, int *err, gchar **err_info)
{
@ -149,6 +248,7 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
int i;
int first;
mp2t_filetype_t *mp2t;
guint64 bitrate;
if (!wtap_read_bytes(wth->fh, buffer, MP2T_SIZE, err, err_info)) {
@ -171,6 +271,7 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return WTAP_OPEN_ERROR;
}
/* read some packets and make sure they all start with a sync byte */
do {
if (!wtap_read_bytes(wth->fh, buffer, MP2T_SIZE+trailer_len, err, err_info)) {
@ -212,6 +313,18 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
return WTAP_OPEN_ERROR;
}
/* Ensure there is a valid bitrate */
bitrate = mp2t_bits_per_second(wth, err, err_info);
if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
return WTAP_OPEN_ERROR;
}
if (0 == bitrate) {
/* We don't have a real bitrate, so we'll default to something reasonable. */
bitrate = MP2T_QAM64_BITRATE;
}
wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_MPEG_2_TS;
wth->file_encap = WTAP_ENCAP_MPEG_2_TS;
wth->file_tsprec = WTAP_TSPREC_NSEC;
@ -224,6 +337,7 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
wth->priv = mp2t;
mp2t->start_offset = first;
mp2t->trailer_len = trailer_len;
mp2t->bitrate = bitrate;
return WTAP_OPEN_MINE;
}