From 66be80d6105fa7e54ad8d23b33ad4ec8f3339b0b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= Date: Fri, 3 Dec 2010 13:26:42 +0000 Subject: mpegtsenc: Improve PCR generation and output 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 --- libavformat/mpegtsenc.c | 54 +++++++++++++++++++++++++++---------------------- 1 file changed, 30 insertions(+), 24 deletions(-) diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c index 2d1fd40..bfd21db 100644 --- a/libavformat/mpegtsenc.c +++ b/libavformat/mpegtsenc.c @@ -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); } -- cgit v1.1