From f1611329ef64ac7893c3da8063784e1fdffdf871 Mon Sep 17 00:00:00 2001
From: Dave Chapman <dave@dchapman.com>
Date: Wed, 25 Jun 2014 21:36:51 +0100
Subject: [PATCH] muxer_pass: Change PAT and PMT rewriting code so that it does
 not modify the TS packets in-place.  These are shared buffers (with other
 subscriptions to the same service) and was causing CC errors in the PAT
 packets when there were multiple simultaneous subscriptions to the same
 service using TS passthrough.  Initial patch by adamsutton - see recent IRC
 logs.

---
 src/muxer/muxer_pass.c | 82 ++++++++++++++++++++++++------------------
 1 file changed, 47 insertions(+), 35 deletions(-)

diff --git a/src/muxer/muxer_pass.c b/src/muxer/muxer_pass.c
index 906099a6..916e2459 100644
--- a/src/muxer/muxer_pass.c
+++ b/src/muxer/muxer_pass.c
@@ -217,37 +217,28 @@ pass_muxer_build_pmt(const streaming_start_t *ss, uint8_t *buf0, int maxlen,
 /*
  * Rewrite a PAT packet to only include the service included in the transport stream.
  *
- * This is complicated by the need to deal with PATs that span more than one transport
- * stream packet.  In that scenario, we replace the 2nd and subsequent PAT packets with
- * NULL packets (PID 0x1fff).
- *
+ * Return 0 if packet can be dropped (i.e. isn't the starting packet
+ * in section or doesn't contain the currently active PAT)
  */
 
 static int
 pass_muxer_rewrite_pat(pass_muxer_t* pm, unsigned char* tsb)
 {
   int pusi = tsb[1]  & 0x40;
+  int cur  = tsb[10] & 0x01;
 
-  /* NULL packet */
-  if (!pusi) {
-    tsb[1] = 0x1f;
-    memset(tsb+2, 0xff, 186);
+  /* Ignore next packet or not start */
+  if (!pusi || !cur)
     return 0;
-  }
 
-  /* Ignore Next (TODO: should we wipe it?) */
-  if (!(tsb[10] & 0x1)) {
-    return 0;
-  }
-    
   /* Some sanity checks */
   if (tsb[4]) {
     tvherror("pass", "Unsupported PAT format - pointer_to_data %d", tsb[4]);
-    return 1;
+    return -1;
   }
   if (tsb[12]) {
     tvherror("pass", "Multi-section PAT not supported");
-    return 2;
+    return -2;
   }
 
   /* Rewrite continuity counter, in case this is a multi-packet PAT (we discard all but the first packet) */
@@ -266,7 +257,7 @@ pass_muxer_rewrite_pat(pass_muxer_t* pm, unsigned char* tsb)
 
   memset(tsb + 21, 0xff, 167); /* Wipe rest of packet */
 
-  return 0;
+  return 1;
 }
 
 /**
@@ -429,39 +420,60 @@ static void
 pass_muxer_write_ts(muxer_t *m, pktbuf_t *pb)
 {
   pass_muxer_t *pm = (pass_muxer_t*)m;
-  unsigned char* tsb;
+  int e;
+  uint8_t tmp[188], *tsb, *pkt = pb->pb_data;
+  size_t  len = pb->pb_size;
   
   /* Rewrite PAT/PMT in operation */
   if (pm->m_config.m_flags & (MC_REWRITE_PAT | MC_REWRITE_PMT)) {
-
     tsb = pb->pb_data;
+    len = 0;
     while (tsb < pb->pb_data + pb->pb_size) {
       int pid = (tsb[1] & 0x1f) << 8 | tsb[2];
 
-      /* PAT */
-      if (pm->m_config.m_flags & MC_REWRITE_PAT && pid == 0) {
-        if (pass_muxer_rewrite_pat(pm, tsb)) {
-          tvherror("pass", "PAT rewrite failed, disabling");
-          pm->m_config.m_flags &= ~MC_REWRITE_PAT;
-        }
-      /* PMT */
-      } else if (pm->m_config.m_flags & MC_REWRITE_PMT && pid == pm->pm_pmt_pid) {
-        if (tsb[1] & 0x40) { /* pusi - the first PMT packet */  
-          memcpy(tsb, pm->pm_pmt, 188);
-          tsb[3] = (pm->pm_pmt[3] & 0xf0) | pm->pm_pmt_cc;
+      /* Process */
+      if ( ((pm->m_config.m_flags & MC_REWRITE_PAT) && (pid == 0)) ||
+           ((pm->m_config.m_flags & MC_REWRITE_PMT) &&
+            (pid == pm->pm_pmt_pid)) ) {
+
+        /* Flush */
+        if (len)
+          pass_muxer_write(m, pkt, len);
+
+        /* Store new start point (after this packet) */
+        pkt = tsb + 188;
+        len = 0;
+
+        /* PAT */
+        if (pid == 0) {
+          memcpy(tmp, tsb, sizeof(tmp));
+          e = pass_muxer_rewrite_pat(pm, tmp);
+          if (e < 0) {
+            tvherror("pass", "PAT rewrite failed, disabling");
+            pm->m_config.m_flags &= ~MC_REWRITE_PAT;
+          }
+          if (e)
+            pass_muxer_write(m, tmp, 188);
+
+        /* PMT */
+        } else if (tsb[1] & 0x40) { /* pusi - the first PMT packet */
+          pm->pm_pmt[3] = (pm->pm_pmt[3] & 0xf0) | pm->pm_pmt_cc;
           pm->pm_pmt_cc = (pm->pm_pmt_cc + 1) & 0xf;
-        } else {
-          /* Nullify packet */
-          tsb[1] = 0x1f;
-          memset(tsb+2, 0xff, 186);
+          pass_muxer_write(m, pm->pm_pmt, 188);
         }
+
+      /* Record */
+      } else {
+        len += 188;
       }
 
+      /* Next packet */
       tsb += 188;
     }
   }
 
-  pass_muxer_write(m, pb->pb_data, pb->pb_size);
+  if (len)
+    pass_muxer_write(m, pkt, len);
 }