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https://gitlab.freedesktop.org/gstreamer/gstreamer.git
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mpegtsmux: improve m2ts timestamp interpolation
* a known PCR should really belong to a packet holding that PCR * interpolation can be extended backward for initial packets (PAT, PMT)
This commit is contained in:
Mark Nauwelaerts
parent
8637fd69e5
commit
ead42a5e27
4 changed files with 60 additions and 53 deletions
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@ -284,7 +284,7 @@ mpegtsmux_reset (MpegTsMux * mux, gboolean alloc)
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mux->first = TRUE;
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mux->last_flow_ret = GST_FLOW_OK;
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mux->first_pcr = TRUE;
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mux->previous_pcr = -1;
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mux->last_ts = 0;
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mux->is_delta = TRUE;
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@ -1203,7 +1203,7 @@ new_packet_m2ts (MpegTsMux * mux, guint8 * data, guint len, gint64 new_pcr)
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GST_BUFFER_TIMESTAMP (buf) = mux->last_ts;
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if (new_pcr < 0) {
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/* If theres no pcr in current ts packet then just add the packet
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/* If there is no pcr in current ts packet then just add the packet
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to the adapter for later output when we see a PCR */
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GST_LOG_OBJECT (mux, "Accumulating non-PCR packet");
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gst_adapter_push (mux->adapter, buf);
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@ -1212,57 +1212,53 @@ new_packet_m2ts (MpegTsMux * mux, guint8 * data, guint len, gint64 new_pcr)
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chunk_bytes = gst_adapter_available (mux->adapter);
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/* We have a new PCR, output anything in the adapter */
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if (mux->first_pcr) {
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/* We can't generate sensible timestamps for anything that might
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* be in the adapter preceding the first PCR and will hit a divide
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* by zero, so empty the adapter. This is probably a null op. */
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gst_adapter_clear (mux->adapter);
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/* Warn if we threw anything away */
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if (chunk_bytes) {
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GST_ELEMENT_WARNING (mux, STREAM, MUX,
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("Discarding %d bytes from stream preceding first PCR",
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chunk_bytes / M2TS_PACKET_LENGTH * NORMAL_TS_PACKET_LENGTH),
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(NULL));
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chunk_bytes = 0;
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}
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mux->first_pcr = FALSE;
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/* no first interpolation point yet, then this is the one,
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* otherwise it is the second interpolation point */
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if (mux->previous_pcr < 0 && chunk_bytes) {
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mux->previous_pcr = new_pcr;
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mux->previous_offset = chunk_bytes;
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GST_LOG_OBJECT (mux, "Accumulating non-PCR packet");
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gst_adapter_push (mux->adapter, buf);
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return TRUE;
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}
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if (chunk_bytes) {
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/* Start the PCR offset counting at 192 bytes: At the end of the packet
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* that had the last PCR */
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guint64 pcr_bytes = M2TS_PACKET_LENGTH, ts_rate;
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/* interpolate if needed, and 2 points available */
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if (chunk_bytes && (new_pcr != mux->previous_pcr)) {
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gint64 offset = 0;
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/* Include the pending packet size to get the ts_rate right */
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chunk_bytes += M2TS_PACKET_LENGTH;
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GST_LOG_OBJECT (mux, "Processing pending packets; "
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"previous pcr %" G_GINT64_FORMAT ", previous offset %d, "
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"current pcr %" G_GINT64_FORMAT ", current offset %d",
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mux->previous_pcr, (gint) mux->previous_offset,
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new_pcr, (gint) chunk_bytes);
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/* calculate rate based on latest and previous pcr values */
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ts_rate = gst_util_uint64_scale (chunk_bytes, CLOCK_FREQ_SCR,
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(new_pcr - mux->previous_pcr));
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GST_LOG_OBJECT (mux, "Processing pending packets with ts_rate %"
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G_GUINT64_FORMAT, ts_rate);
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while (1) {
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g_assert (chunk_bytes > mux->previous_offset);
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while (offset < chunk_bytes) {
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guint64 cur_pcr, ts;
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/* Loop, pulling packets of the adapter, updating their 4 byte
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* timestamp header and pushing */
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/* The header is the bottom 30 bits of the PCR, apparently not
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* encoded into base + ext as in the packets themselves, so
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* we can just interpolate, mask and insert */
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cur_pcr = (mux->previous_pcr +
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gst_util_uint64_scale (pcr_bytes, CLOCK_FREQ_SCR, ts_rate));
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/* interpolate PCR */
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if (G_LIKELY (offset >= mux->previous_offset))
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cur_pcr = mux->previous_pcr +
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gst_util_uint64_scale (offset - mux->previous_offset,
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new_pcr - mux->previous_pcr, chunk_bytes - mux->previous_offset);
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else
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cur_pcr = mux->previous_pcr -
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gst_util_uint64_scale (mux->previous_offset - offset,
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new_pcr - mux->previous_pcr, chunk_bytes - mux->previous_offset);
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ts = gst_adapter_prev_timestamp (mux->adapter, NULL);
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out_buf = gst_adapter_take_buffer (mux->adapter, M2TS_PACKET_LENGTH);
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if (G_UNLIKELY (!out_buf))
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break;
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g_assert (out_buf);
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offset += M2TS_PACKET_LENGTH;
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gst_buffer_set_caps (out_buf, GST_PAD_CAPS (mux->srcpad));
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GST_BUFFER_TIMESTAMP (out_buf) = ts;
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/* Write the 4 byte timestamp value, bottom 30 bits only = PCR */
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/* The header is the bottom 30 bits of the PCR, apparently not
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* encoded into base + ext as in the packets themselves */
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GST_WRITE_UINT32_BE (GST_BUFFER_DATA (out_buf), cur_pcr & 0x3FFFFFFF);
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GST_LOG_OBJECT (mux, "Outputting a packet of length %d PCR %"
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@ -1272,7 +1268,6 @@ new_packet_m2ts (MpegTsMux * mux, guint8 * data, guint len, gint64 new_pcr)
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mux->last_flow_ret = ret;
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return FALSE;
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}
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pcr_bytes += M2TS_PACKET_LENGTH;
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}
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}
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@ -1288,7 +1283,10 @@ new_packet_m2ts (MpegTsMux * mux, guint8 * data, guint len, gint64 new_pcr)
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return FALSE;
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}
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if (new_pcr != mux->previous_pcr) {
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mux->previous_pcr = new_pcr;
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mux->previous_offset = -M2TS_PACKET_LENGTH;
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}
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return TRUE;
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}
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@ -153,8 +153,8 @@ struct MpegTsMux {
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GstClockTime last_ts;
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/* m2ts specific */
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gboolean first_pcr;
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gint64 previous_pcr;
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gint64 previous_offset;
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GstAdapter *adapter;
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/* output buffer aggregation */
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@ -108,6 +108,10 @@
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/* Times per second to write PCR */
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#define TSMUX_DEFAULT_PCR_FREQ (25)
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/* Base for all written PCR and DTS/PTS,
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* so we have some slack to go backwards */
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#define CLOCK_BASE (TSMUX_CLOCK_FREQ * 10 * 360)
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static gboolean tsmux_write_pat (TsMux * mux);
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static gboolean tsmux_write_pmt (TsMux * mux, TsMuxProgram * program);
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@ -431,13 +435,13 @@ tsmux_find_stream (TsMux * mux, guint16 pid)
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}
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static gboolean
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tsmux_packet_out (TsMux * mux)
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tsmux_packet_out (TsMux * mux, gint64 pcr)
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{
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if (G_UNLIKELY (mux->write_func == NULL))
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return TRUE;
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return mux->write_func (mux->packet_buf, TSMUX_PACKET_LENGTH,
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mux->write_func_data, mux->new_pcr);
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mux->write_func_data, pcr);
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}
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/*
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@ -702,18 +706,17 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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guint payload_len, payload_offs;
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TsMuxPacketInfo *pi = &stream->pi;
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gboolean res;
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gint64 cur_pcr = -1;
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mux->new_pcr = -1;
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g_return_val_if_fail (mux != NULL, FALSE);
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g_return_val_if_fail (stream != NULL, FALSE);
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if (tsmux_stream_is_pcr (stream)) {
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gint64 cur_pcr = 0;
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gint64 cur_pts = tsmux_stream_get_pts (stream);
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gboolean write_pat;
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GList *cur;
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cur_pcr = 0;
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if (cur_pts != -1) {
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TS_DEBUG ("TS for PCR stream is %" G_GINT64_FORMAT, cur_pts);
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}
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@ -724,6 +727,8 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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cur_pcr = (cur_pts - TSMUX_PCR_OFFSET) *
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(TSMUX_SYS_CLOCK_FREQ / TSMUX_CLOCK_FREQ);
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cur_pcr += CLOCK_BASE * (TSMUX_SYS_CLOCK_FREQ / TSMUX_CLOCK_FREQ);
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/* Need to decide whether to write a new PCR in this packet */
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if (stream->last_pcr == -1 ||
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(cur_pcr - stream->last_pcr >
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@ -733,7 +738,8 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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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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stream->last_pcr = cur_pcr;
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mux->new_pcr = cur_pcr;
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} else {
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cur_pcr = -1;
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}
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/* check if we need to rewrite pat */
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@ -771,8 +777,13 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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}
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pi->packet_start_unit_indicator = tsmux_stream_at_pes_start (stream);
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if (pi->packet_start_unit_indicator)
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if (pi->packet_start_unit_indicator) {
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tsmux_stream_initialize_pes_packet (stream);
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if (stream->dts != -1)
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stream->dts += CLOCK_BASE;
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if (stream->pts != -1)
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stream->pts += CLOCK_BASE;
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}
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pi->stream_avail = tsmux_stream_bytes_avail (stream);
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if (!tsmux_write_ts_header (mux->packet_buf, pi, &payload_len, &payload_offs))
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@ -782,7 +793,7 @@ tsmux_write_stream_packet (TsMux * mux, TsMuxStream * stream)
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payload_len))
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return FALSE;
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res = tsmux_packet_out (mux);
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res = tsmux_packet_out (mux, cur_pcr);
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/* Reset all dynamic flags */
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stream->pi.flags &= TSMUX_PACKET_FLAG_PES_FULL_HEADER;
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@ -853,11 +864,10 @@ tsmux_write_section (TsMux * mux, TsMuxSection * section)
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cur_in += payload_len;
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payload_remain -= payload_len;
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if (G_UNLIKELY (!tsmux_packet_out (mux))) {
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mux->new_pcr = -1;
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/* we do not write PCR in section */
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if (G_UNLIKELY (!tsmux_packet_out (mux, -1))) {
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return FALSE;
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}
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mux->new_pcr = -1;
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}
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return TRUE;
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@ -167,7 +167,6 @@ struct TsMux {
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/* scratch space for writing ES_info descriptors */
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guint8 es_info_buf[TSMUX_MAX_ES_INFO_LENGTH];
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gint64 new_pcr;
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};
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/* create/free new muxer session */
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