[FFmpeg-devel] [PATCH] avformat/mpegtsenc: fix PCR generation intervals

[Marton Balint]

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 PCR for CBR and packet DTS values for VBR streams,
so the default 20ms PCR retransmission time is now respected for both CBR and
VBR.

Signed-off-by: Marton Balint <cus at passwd.hu>
---
 libavformat/mpegtsenc.c | 60 +++++++++++++++----------------------------------
 tests/ref/lavf/ts       |  2 +-
 2 files changed, 19 insertions(+), 43 deletions(-)

diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
index 02651308f8..a501807711 100644
--- a/libavformat/mpegtsenc.c
+++ b/libavformat/mpegtsenc.c
@@ -237,10 +237,9 @@ typedef struct MpegTSWriteStream {
     int payload_flags;
     uint8_t *payload;
     AVFormatContext *amux;
-    AVRational user_tb;
 
-    int pcr_packet_count;
-    int pcr_packet_period;
+    int pcr_period;
+    int64_t last_pcr;
 
     /* For Opus */
     int opus_queued_samples;
@@ -792,32 +791,9 @@ static void enable_pcr_generation_for_stream(AVFormatContext *s, AVStream *pcr_s
     MpegTSWrite *ts = s->priv_data;
     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);
-    } else {
-        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);
-            }
-        } 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);
-        }
-        if (!ts_st->pcr_packet_period)
-            ts_st->pcr_packet_period = 1;
-    }
-
+    ts_st->pcr_period = av_rescale(ts->pcr_period, PCR_TIME_BASE, 1000);
     // output a PCR as soon as possible
-    ts_st->pcr_packet_count = ts_st->pcr_packet_period;
+    ts_st->last_pcr   = av_rescale(s->max_delay, PCR_TIME_BASE, AV_TIME_BASE) - ts_st->pcr_period;
 }
 
 static void select_pcr_streams(AVFormatContext *s)
@@ -907,7 +883,6 @@ 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);
@@ -1183,7 +1158,6 @@ 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;
 
@@ -1194,18 +1168,24 @@ 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;
-                write_pcr = 1;
+        if (ts_st->pcr_period) {
+            if (ts->mux_rate > 1) {
+                pcr = get_pcr(ts, s->pb);
+                if (pcr - ts_st->last_pcr >= ts_st->pcr_period)
+                    write_pcr = 1;
+            } else if (dts != AV_NOPTS_VALUE) {
+                pcr = (dts - delay) * 300;
+                if (pcr - ts_st->last_pcr >= ts_st->pcr_period && is_start)
+                    write_pcr = 1;
             }
+            if (write_pcr)
+                ts_st->last_pcr = FFMAX(pcr - ts_st->pcr_period, ts_st->last_pcr + ts_st->pcr_period);
         }
 
         if (ts->mux_rate > 1 && dts != AV_NOPTS_VALUE &&
@@ -1236,7 +1216,7 @@ 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 +1225,6 @@ 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));
diff --git a/tests/ref/lavf/ts b/tests/ref/lavf/ts
index 09960f84d3..8644c260e3 100644
--- a/tests/ref/lavf/ts
+++ b/tests/ref/lavf/ts
@@ -1,3 +1,3 @@
-38f4b14d43a0e416be8d598628997cbc *tests/data/lavf/lavf.ts
+3eee8c2ef073ecdb2b85f40bb9b2e652 *tests/data/lavf/lavf.ts
 407020 tests/data/lavf/lavf.ts
 tests/data/lavf/lavf.ts CRC=0x71287e25
-- 
2.16.4