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mpegtsmux: Improve PCR/SI scheduling.
Change PCR / SI scheduling so that instead of checking if the current PCR is larger than the next target time, instead check if the PCR of the next packet would be too late, so PCR and SI are always scheduled earlier than the target, not later. There are still cases where PCR can be written too late though, because we don't check before each output packet. Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2073>
This commit is contained in:
Jan Schmidt
GStreamer Marge Bot
parent
49c61338d6
commit
3201575d2a
1 changed files with 108 additions and 72 deletions
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@ -101,6 +101,10 @@
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#define TSMUX_DEFAULT_NETWORK_ID 0x0001
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#define TSMUX_DEFAULT_TS_ID 0x0001
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/* The last byte of the PCR in the header defines the byte position
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* at which PCR should be calculated */
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#define PCR_BYTE_OFFSET 11
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/* HACK: We use a fixed buffering offset for the PCR at the moment -
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* this is the amount 'in advance' of the stream that the PCR sits.
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* 1/8 second atm */
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@ -1248,6 +1252,7 @@ ts_to_pcr (gint64 ts)
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return (ts - TSMUX_PCR_OFFSET) * (TSMUX_SYS_CLOCK_FREQ / TSMUX_CLOCK_FREQ);
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}
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/* Calculate the PCR to write into the current packet */
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static gint64
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get_current_pcr (TsMux * mux, gint64 cur_ts)
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{
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@ -1257,25 +1262,48 @@ get_current_pcr (TsMux * mux, gint64 cur_ts)
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if (mux->first_pcr_ts == G_MININT64) {
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g_assert (cur_ts != G_MININT64);
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mux->first_pcr_ts = cur_ts;
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GST_DEBUG ("First PCR offset is %" G_GUINT64_FORMAT, cur_ts);
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}
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return ts_to_pcr (mux->first_pcr_ts) +
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gst_util_uint64_scale (mux->n_bytes * 8, TSMUX_SYS_CLOCK_FREQ,
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mux->bitrate);
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gst_util_uint64_scale ((mux->n_bytes + PCR_BYTE_OFFSET) * 8,
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TSMUX_SYS_CLOCK_FREQ, mux->bitrate);
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}
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/* Predict the PCR at the next packet if possible */
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static gint64
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get_next_pcr (TsMux * mux, gint64 cur_ts)
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{
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if (!mux->bitrate)
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return ts_to_pcr (cur_ts);
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if (mux->first_pcr_ts == G_MININT64) {
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g_assert (cur_ts != G_MININT64);
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mux->first_pcr_ts = cur_ts;
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GST_DEBUG ("First PCR offset is %" G_GUINT64_FORMAT, cur_ts);
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}
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return ts_to_pcr (mux->first_pcr_ts) +
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gst_util_uint64_scale ((mux->n_bytes + TSMUX_PACKET_LENGTH +
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PCR_BYTE_OFFSET) * 8, TSMUX_SYS_CLOCK_FREQ, mux->bitrate);
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}
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static gint64
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write_new_pcr (TsMux * mux, TsMuxStream * stream, gint64 cur_pcr)
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write_new_pcr (TsMux * mux, TsMuxStream * stream, gint64 cur_pcr,
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gint64 next_pcr)
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{
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if (stream->next_pcr == -1 || cur_pcr > stream->next_pcr) {
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if (stream->next_pcr == -1 || next_pcr > stream->next_pcr) {
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stream->pi.flags |=
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TSMUX_PACKET_FLAG_ADAPTATION | TSMUX_PACKET_FLAG_WRITE_PCR;
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stream->pi.pcr = cur_pcr;
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if (stream->next_pcr == -1)
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if (stream->next_pcr != -1 && cur_pcr >= stream->next_pcr) {
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GST_WARNING ("Writing PCR %" G_GUINT64_FORMAT " missed the target %"
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G_GUINT64_FORMAT " by %f ms", cur_pcr, stream->next_pcr,
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(double) (cur_pcr - stream->next_pcr) / 27000.0);
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}
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/* Next PCR deadline is now plus the scheduled interval */
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stream->next_pcr = cur_pcr + mux->pcr_interval * 300;
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else
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stream->next_pcr += mux->pcr_interval * 300;
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} else {
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cur_pcr = -1;
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}
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@ -1289,48 +1317,48 @@ rewrite_si (TsMux * mux, gint64 cur_ts)
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gboolean write_pat;
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gboolean write_si;
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GList *cur;
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gint64 cur_pcr;
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gint64 next_pcr;
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cur_pcr = get_current_pcr (mux, cur_ts);
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next_pcr = get_next_pcr (mux, cur_ts);
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/* check if we need to rewrite pat */
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if (mux->next_pat_pcr == -1 || mux->pat_changed)
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write_pat = TRUE;
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else if (cur_pcr > mux->next_pat_pcr)
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else if (next_pcr > mux->next_pat_pcr)
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write_pat = TRUE;
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else
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write_pat = FALSE;
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if (write_pat) {
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if (mux->next_pat_pcr == -1)
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mux->next_pat_pcr = cur_pcr + mux->pat_interval * 300;
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mux->next_pat_pcr = next_pcr + mux->pat_interval * 300;
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else
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mux->next_pat_pcr += mux->pat_interval * 300;
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if (!tsmux_write_pat (mux))
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return FALSE;
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cur_pcr = get_current_pcr (mux, cur_ts);
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next_pcr = get_next_pcr (mux, cur_ts);
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}
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/* check if we need to rewrite sit */
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if (mux->next_si_pcr == -1 || mux->si_changed)
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write_si = TRUE;
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else if (cur_pcr > mux->next_si_pcr)
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else if (next_pcr > mux->next_si_pcr)
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write_si = TRUE;
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else
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write_si = FALSE;
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if (write_si) {
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if (mux->next_si_pcr == -1)
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mux->next_si_pcr = cur_pcr + mux->si_interval * 300;
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mux->next_si_pcr = next_pcr + mux->si_interval * 300;
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else
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mux->next_si_pcr += mux->si_interval * 300;
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if (!tsmux_write_si (mux))
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return FALSE;
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cur_pcr = get_current_pcr (mux, cur_ts);
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next_pcr = get_current_pcr (mux, cur_ts);
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}
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/* check if we need to rewrite any of the current pmts */
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@ -1340,28 +1368,28 @@ rewrite_si (TsMux * mux, gint64 cur_ts)
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if (program->next_pmt_pcr == -1 || program->pmt_changed)
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write_pmt = TRUE;
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else if (cur_pcr > program->next_pmt_pcr)
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else if (next_pcr > program->next_pmt_pcr)
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write_pmt = TRUE;
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else
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write_pmt = FALSE;
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if (write_pmt) {
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if (program->next_pmt_pcr == -1)
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program->next_pmt_pcr = cur_pcr + program->pmt_interval * 300;
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program->next_pmt_pcr = next_pcr + program->pmt_interval * 300;
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else
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program->next_pmt_pcr += program->pmt_interval * 300;
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if (!tsmux_write_pmt (mux, program))
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return FALSE;
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cur_pcr = get_current_pcr (mux, cur_ts);
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next_pcr = get_current_pcr (mux, cur_ts);
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}
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if (program->scte35_pid != 0) {
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gboolean write_scte_null = FALSE;
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if (program->next_scte35_pcr == -1)
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write_scte_null = TRUE;
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else if (cur_pcr > program->next_scte35_pcr)
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else if (next_pcr > program->next_scte35_pcr)
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write_scte_null = TRUE;
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if (write_scte_null) {
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@ -1369,7 +1397,7 @@ rewrite_si (TsMux * mux, gint64 cur_ts)
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program->next_scte35_pcr);
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if (program->next_scte35_pcr == -1)
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program->next_scte35_pcr =
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cur_pcr + program->scte35_null_interval * 300;
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next_pcr + program->scte35_null_interval * 300;
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else
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program->next_scte35_pcr += program->scte35_null_interval * 300;
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GST_DEBUG ("next scte35 NOW pcr %" G_GINT64_FORMAT,
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@ -1378,7 +1406,7 @@ rewrite_si (TsMux * mux, gint64 cur_ts)
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if (!tsmux_write_scte_null (mux, program))
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return FALSE;
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cur_pcr = get_current_pcr (mux, cur_ts);
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next_pcr = get_current_pcr (mux, cur_ts);
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}
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}
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}
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@ -1393,36 +1421,38 @@ pad_stream (TsMux * mux, TsMuxStream * stream, gint64 cur_ts)
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GstBuffer *buf = NULL;
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GstMapInfo map;
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gboolean ret = TRUE;
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GstClockTimeDiff diff;
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guint64 start_n_bytes;
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if (!mux->bitrate)
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goto done;
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do {
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if (GST_CLOCK_STIME_IS_VALID (cur_ts)) {
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GstClockTimeDiff diff;
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if (!GST_CLOCK_STIME_IS_VALID (cur_ts))
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goto done;
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if (!GST_CLOCK_STIME_IS_VALID (stream->first_ts))
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stream->first_ts = cur_ts;
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diff = GST_CLOCK_DIFF (stream->first_ts, cur_ts);
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if (diff == 0)
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goto done;
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if (diff) {
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start_n_bytes = mux->n_bytes;
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do {
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GST_LOG ("Transport stream bitrate: %" G_GUINT64_FORMAT " over %"
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G_GUINT64_FORMAT " bytes, duration %" GST_TIME_FORMAT,
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gst_util_uint64_scale (mux->n_bytes * 8, TSMUX_CLOCK_FREQ, diff),
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mux->n_bytes, GST_TIME_ARGS (diff * GST_SECOND / TSMUX_CLOCK_FREQ));
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/* calculate what the overall bitrate will be if we add 1 more packet */
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bitrate =
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gst_util_uint64_scale (mux->n_bytes * 8, TSMUX_CLOCK_FREQ, diff);
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gst_util_uint64_scale ((mux->n_bytes + TSMUX_PACKET_LENGTH) * 8,
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TSMUX_CLOCK_FREQ, diff);
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GST_LOG ("Transport stream bitrate: %" G_GUINT64_FORMAT, bitrate);
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if (bitrate < mux->bitrate) {
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if (bitrate <= mux->bitrate) {
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gint64 new_pcr;
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guint payload_len, payload_offs;
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GST_LOG ("Padding transport stream");
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if (!rewrite_si (mux, cur_ts)) {
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ret = FALSE;
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goto done;
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}
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if (!tsmux_get_buffer (mux, &buf)) {
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ret = FALSE;
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goto done;
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@ -1432,11 +1462,18 @@ pad_stream (TsMux * mux, TsMuxStream * stream, gint64 cur_ts)
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if ((new_pcr =
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write_new_pcr (mux, stream, get_current_pcr (mux,
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cur_ts)) != -1))
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cur_ts), get_next_pcr (mux, cur_ts)) != -1)) {
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GST_LOG ("Writing PCR-only packet on PID 0x%04x", stream->pi.pid);
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tsmux_write_ts_header (mux, map.data, &stream->pi, &payload_len,
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&payload_offs, 0);
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else
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} else {
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GST_LOG ("Writing null stuffing packet");
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if (!rewrite_si (mux, cur_ts)) {
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ret = FALSE;
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goto done;
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}
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tsmux_write_null_ts_header (map.data);
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}
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gst_buffer_unmap (buf, &map);
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@ -1445,14 +1482,12 @@ pad_stream (TsMux * mux, TsMuxStream * stream, gint64 cur_ts)
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if (!(ret = tsmux_packet_out (mux, buf, new_pcr)))
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goto done;
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}
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} else {
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break;
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}
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} else {
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break;
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}
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} while (bitrate < mux->bitrate);
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if (mux->n_bytes != start_n_bytes) {
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GST_LOG ("Finished padding the mux");
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}
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done:
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return ret;
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}
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@ -1481,7 +1516,6 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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if (tsmux_stream_is_pcr (stream)) {
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gint64 cur_ts = CLOCK_BASE;
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if (tsmux_stream_get_dts (stream) != G_MININT64)
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cur_ts += tsmux_stream_get_dts (stream);
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else
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@ -1493,7 +1527,9 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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if (!pad_stream (mux, stream, cur_ts))
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goto fail;
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new_pcr = write_new_pcr (mux, stream, get_current_pcr (mux, cur_ts));
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new_pcr =
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write_new_pcr (mux, stream, get_current_pcr (mux, cur_ts),
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get_next_pcr (mux, cur_ts));
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}
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pi->packet_start_unit_indicator = tsmux_stream_at_pes_start (stream);
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