virtualenv/FFmpeg
1
0
Fork 0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2024-12-23 12:43:46 +02:00
Code Issues Releases Activity

mpegtsenc: Improve PCR generation and output

Browse Source 
This fixes PCR drift due to accumulating TS_PACKET_SIZE*8*90000LL/ts->mux_rate each packet, due to rounding errors when mux_rate does not evenly divide 135360000.
This patch also increases the PCR precision to 27 MHz from 90 kHz and takes the location of the PCR data into account (+11 bytes according to the spec).

Originally committed as revision 25864 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Tomas Härdin 2010-12-03 13:26:42 +00:00
parent 77b7c334be
commit 66be80d610
1 changed files with 30 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
libavformat/mpegtsenc.c
View File

@ -27,6 +27,8 @@
#include "mpegts.h"
#include "adts.h"
#define PCR_TIME_BASE 27000000
/* write DVB SI sections */
/*********************************************/
@ -60,7 +62,7 @@ typedef struct MpegTSWrite {
int nb_services;
int onid;
int tsid;
uint64_t cur_pcr;
int64_t first_pcr;
int mux_rate; ///< set to 1 when VBR
} MpegTSWrite;
@ -109,8 +111,6 @@ static void mpegts_write_section(MpegTSSection *s, uint8_t *buf, int len)
buf_ptr += len1;
len -= len1;
ts->cur_pcr += TS_PACKET_SIZE*8*90000LL/ts->mux_rate;
}
}
@ -489,7 +489,7 @@ static int mpegts_write_header(AVFormatContext *s)
ts->pat_packet_period = (ts->mux_rate * PAT_RETRANS_TIME) /
(TS_PACKET_SIZE * 8 * 1000);
ts->cur_pcr = av_rescale(s->max_delay, 90000, AV_TIME_BASE);
ts->first_pcr = av_rescale(s->max_delay, PCR_TIME_BASE, AV_TIME_BASE);
} else {
/* Arbitrary values, PAT/PMT could be written on key frames */
ts->sdt_packet_period = 200;
@ -556,6 +556,26 @@ static void retransmit_si_info(AVFormatContext *s)
}
}
static int64_t get_pcr(const MpegTSWrite *ts, ByteIOContext *pb)
{
return av_rescale(url_ftell(pb) + 11, 8 * PCR_TIME_BASE, ts->mux_rate) +
ts->first_pcr;
}
static uint8_t* write_pcr_bits(uint8_t *buf, int64_t pcr)
{
int64_t pcr_low = pcr % 300, pcr_high = pcr / 300;
*buf++ = pcr_high >> 25;
*buf++ = pcr_high >> 17;
*buf++ = pcr_high >> 9;
*buf++ = pcr_high >> 1;
*buf++ = ((pcr_high & 1) << 7) | (pcr_low >> 8);
*buf++ = pcr_low;
return buf;
}
/* Write a single null transport stream packet */
static void mpegts_insert_null_packet(AVFormatContext *s)
{
@ -570,7 +590,6 @@ static void mpegts_insert_null_packet(AVFormatContext *s)
*q++ = 0x10;
memset(q, 0x0FF, TS_PACKET_SIZE - (q - buf));
put_buffer(s->pb, buf, TS_PACKET_SIZE);
ts->cur_pcr += TS_PACKET_SIZE*8*90000LL/ts->mux_rate;
}
/* Write a single transport stream packet with a PCR and no payload */
@ -579,7 +598,6 @@ static void mpegts_insert_pcr_only(AVFormatContext *s, AVStream *st)
MpegTSWrite *ts = s->priv_data;
MpegTSWriteStream *ts_st = st->priv_data;
uint8_t *q;
uint64_t pcr = ts->cur_pcr;
uint8_t buf[TS_PACKET_SIZE];
q = buf;
@ -592,17 +610,11 @@ static void mpegts_insert_pcr_only(AVFormatContext *s, AVStream *st)
*q++ = 0x10; /* Adaptation flags: PCR present */
/* PCR coded into 6 bytes */
*q++ = pcr >> 25;
*q++ = pcr >> 17;
*q++ = pcr >> 9;
*q++ = pcr >> 1;
*q++ = (pcr & 1) << 7;
*q++ = 0;
q = write_pcr_bits(q, get_pcr(ts, s->pb));
/* stuffing bytes */
memset(q, 0xFF, TS_PACKET_SIZE - (q - buf));
put_buffer(s->pb, buf, TS_PACKET_SIZE);
ts->cur_pcr += TS_PACKET_SIZE*8*90000LL/ts->mux_rate;
}
static void write_pts(uint8_t *q, int fourbits, int64_t pts)
@ -653,7 +665,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
}
if (ts->mux_rate > 1 && dts != AV_NOPTS_VALUE &&
(dts - (int64_t)ts->cur_pcr) > delay) {
(dts - get_pcr(ts, s->pb)/300) > delay) {
/* pcr insert gets priority over null packet insert */
if (write_pcr)
mpegts_insert_pcr_only(s, st);
@ -675,19 +687,14 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
if (write_pcr) {
// add 11, pcr references the last byte of program clock reference base
if (ts->mux_rate > 1)
pcr = ts->cur_pcr + (4+7)*8*90000LL / ts->mux_rate;
pcr = get_pcr(ts, s->pb);
else
pcr = dts - delay;
if (dts != AV_NOPTS_VALUE && dts < pcr)
pcr = (dts - delay)*300;
if (dts != AV_NOPTS_VALUE && dts < pcr / 300)
av_log(s, AV_LOG_WARNING, "dts < pcr, TS is invalid\n");
*q++ = 7; /* AFC length */
*q++ = 0x10; /* flags: PCR present */
*q++ = pcr >> 25;
*q++ = pcr >> 17;
*q++ = pcr >> 9;
*q++ = pcr >> 1;
*q++ = (pcr & 1) << 7;
*q++ = 0;
q = write_pcr_bits(q, pcr);
}
if (is_start) {
int pes_extension = 0;
@ -802,7 +809,6 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
payload += len;
payload_size -= len;
put_buffer(s->pb, buf, TS_PACKET_SIZE);
ts->cur_pcr += TS_PACKET_SIZE*8*90000LL/ts->mux_rate;
}
put_flush_packet(s->pb);
}