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avformat/mpegtsenc: fix PCR generation intervals

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PCR generation was based on counting packets for both CBR and VBR streams.
Couting packets might have worked for CBR streams (when muxrate was specified)
but it only took into account the packets of a service (or the packets of the
PCR stream lately), so even that was problematic for multi program streams.

The new code works on actual timestamps for both CBR and VBR streams. For VBR
streams the behaviour of the old code is simulated by selecting a PCR interval
which is the highest multiple of the frame duration but still less than 100 ms.

It should be trivial to add support for setting the PCR interval for VBR
streams as well in a later patch.

The accuracy of PCR packets for CBR streams was greatly improved by preemtively
sending them at PCR intervals even if sending the payload of another stream
is in progress.

This may fix these tickets:
- #5750
- #7524

Signed-off-by: Marton Balint <cus@passwd.hu>
pull/321/head^2
Marton Balint 6 years ago
parent a4d984ad33
commit 88ac76be79
1 changed files with 54 additions and 36 deletions
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  1. 90
      libavformat/mpegtsenc.c

90
libavformat/mpegtsenc.c
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@ -84,6 +84,7 @@ typedef struct MpegTSWrite {
int onid;
int tsid;
int64_t first_pcr;
int64_t next_pcr;
int mux_rate; ///< set to 1 when VBR
int pes_payload_size;
@ -237,10 +238,9 @@ typedef struct MpegTSWriteStream {
int payload_flags;
uint8_t *payload;
AVFormatContext *amux;
AVRational user_tb;
int pcr_packet_count;
int pcr_packet_period;
int64_t pcr_period; /* PCR period in PCR time base */
int64_t last_pcr;
/* For Opus */
int opus_queued_samples;
@ -793,31 +793,28 @@ static void enable_pcr_generation_for_stream(AVFormatContext *s, AVStream *pcr_s
MpegTSWriteStream *ts_st = pcr_st->priv_data;
if (ts->mux_rate > 1) {
ts_st->pcr_packet_period = (int64_t)ts->mux_rate * ts->pcr_period /
(TS_PACKET_SIZE * 8 * 1000);
ts_st->pcr_period = av_rescale(ts->pcr_period, PCR_TIME_BASE, 1000);
} else {
/* For VBR we select the highest multiple of frame duration which is less than 100 ms. */
int64_t frame_period = 0;
if (pcr_st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
int frame_size = av_get_audio_frame_duration2(pcr_st->codecpar, 0);
if (!frame_size) {
av_log(s, AV_LOG_WARNING, "frame size not set\n");
ts_st->pcr_packet_period =
pcr_st->codecpar->sample_rate / (10 * 512);
} else {
ts_st->pcr_packet_period =
pcr_st->codecpar->sample_rate / (10 * frame_size);
av_log(s, AV_LOG_WARNING, "frame size not set\n");
frame_size = 512;
}
} else {
// max delta PCR 0.1s
// TODO: should be avg_frame_rate
ts_st->pcr_packet_period =
ts_st->user_tb.den / (10 * ts_st->user_tb.num);
frame_period = av_rescale_rnd(frame_size, PCR_TIME_BASE, pcr_st->codecpar->sample_rate, AV_ROUND_UP);
} else if (pcr_st->avg_frame_rate.num) {
frame_period = av_rescale_rnd(pcr_st->avg_frame_rate.den, PCR_TIME_BASE, pcr_st->avg_frame_rate.num, AV_ROUND_UP);
}
if (!ts_st->pcr_packet_period)
ts_st->pcr_packet_period = 1;
if (frame_period > 0 && frame_period <= PCR_TIME_BASE / 10)
ts_st->pcr_period = frame_period * (PCR_TIME_BASE / 10 / frame_period);
else
ts_st->pcr_period = 1;
}
// output a PCR as soon as possible
ts_st->pcr_packet_count = ts_st->pcr_packet_period;
ts_st->last_pcr = ts->first_pcr - ts_st->pcr_period;
}
static void select_pcr_streams(AVFormatContext *s)
@ -843,7 +840,8 @@ static void select_pcr_streams(AVFormatContext *s)
MpegTSWriteStream *ts_st = pcr_st->priv_data;
service->pcr_pid = ts_st->pid;
enable_pcr_generation_for_stream(s, pcr_st);
av_log(s, AV_LOG_VERBOSE, "service %i using PCR in pid=%i\n", service->sid, service->pcr_pid);
av_log(s, AV_LOG_VERBOSE, "service %i using PCR in pid=%i, pcr_period=%"PRId64"ms\n",
service->sid, service->pcr_pid, av_rescale(ts_st->pcr_period, 1000, PCR_TIME_BASE));
}
}
}
@ -907,7 +905,6 @@ static int mpegts_init(AVFormatContext *s)
}
st->priv_data = ts_st;
ts_st->user_tb = st->time_base;
avpriv_set_pts_info(st, 33, 1, 90000);
ts_st->payload = av_mallocz(ts->pes_payload_size);
@ -987,15 +984,15 @@ static int mpegts_init(AVFormatContext *s)
(TS_PACKET_SIZE * 8 * 1000);
ts->pat_packet_period = (int64_t)ts->mux_rate * PAT_RETRANS_TIME /
(TS_PACKET_SIZE * 8 * 1000);
if (ts->copyts < 1)
ts->first_pcr = av_rescale(s->max_delay, PCR_TIME_BASE, AV_TIME_BASE);
} else {
/* Arbitrary values, PAT/PMT will also be written on video key frames */
ts->sdt_packet_period = 200;
ts->pat_packet_period = 40;
}
if (ts->copyts < 1)
ts->first_pcr = av_rescale(s->max_delay, PCR_TIME_BASE, AV_TIME_BASE);
select_pcr_streams(s);
ts->last_pat_ts = AV_NOPTS_VALUE;
@ -1183,7 +1180,6 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
uint8_t *q;
int val, is_start, len, header_len, write_pcr, is_dvb_subtitle, is_dvb_teletext, flags;
int afc_len, stuffing_len;
int64_t pcr = -1; /* avoid warning */
int64_t delay = av_rescale(s->max_delay, 90000, AV_TIME_BASE);
int force_pat = st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && key && !ts_st->prev_payload_key;
@ -1194,16 +1190,42 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
is_start = 1;
while (payload_size > 0) {
int64_t pcr = -1; /* avoid warning */
retransmit_si_info(s, force_pat, dts);
force_pat = 0;
write_pcr = 0;
if (ts_st->pcr_packet_period) {
if (ts->mux_rate > 1 || is_start) // VBR pcr period is based on frames
ts_st->pcr_packet_count++;
if (ts_st->pcr_packet_count >=
ts_st->pcr_packet_period) {
ts_st->pcr_packet_count = 0;
if (ts->mux_rate > 1) {
/* Send PCR packets for all PCR streams if needed */
pcr = get_pcr(ts, s->pb);
if (pcr >= ts->next_pcr) {
int64_t next_pcr = INT64_MAX;
for (int i = 0; i < s->nb_streams; i++) {
/* Make the current stream the last, because for that we
* can insert the pcr into the payload later */
int st2_index = i < st->index ? i : (i + 1 == s->nb_streams ? st->index : i + 1);
AVStream *st2 = s->streams[st2_index];
MpegTSWriteStream *ts_st2 = st2->priv_data;
if (ts_st2->pcr_period) {
if (pcr - ts_st2->last_pcr >= ts_st2->pcr_period) {
ts_st2->last_pcr = FFMAX(pcr - ts_st2->pcr_period, ts_st2->last_pcr + ts_st2->pcr_period);
if (st2 != st) {
mpegts_insert_pcr_only(s, st2);
pcr = get_pcr(ts, s->pb);
} else {
write_pcr = 1;
}
}
next_pcr = FFMIN(next_pcr, ts_st2->last_pcr + ts_st2->pcr_period);
}
}
ts->next_pcr = next_pcr;
}
} else if (ts_st->pcr_period && dts != AV_NOPTS_VALUE) {
pcr = (dts - delay) * 300;
if (pcr - ts_st->last_pcr >= ts_st->pcr_period && is_start) {
ts_st->last_pcr = FFMAX(pcr - ts_st->pcr_period, ts_st->last_pcr + ts_st->pcr_period);
write_pcr = 1;
}
}
@ -1236,7 +1258,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
}
if (key && is_start && pts != AV_NOPTS_VALUE) {
// set Random Access for key frames
if (ts_st->pcr_packet_period)
if (ts_st->pcr_period)
write_pcr = 1;
set_af_flag(buf, 0x40);
q = get_ts_payload_start(buf);
@ -1245,10 +1267,6 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
set_af_flag(buf, 0x10);
q = get_ts_payload_start(buf);
// add 11, pcr references the last byte of program clock reference base
if (ts->mux_rate > 1)
pcr = get_pcr(ts, s->pb);
else
pcr = (dts - delay) * 300;
if (dts != AV_NOPTS_VALUE && dts < pcr / 300)
av_log(s, AV_LOG_WARNING, "dts < pcr, TS is invalid\n");
extend_af(buf, write_pcr_bits(q, pcr));

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