rtpj2kpay: manage T tile invalidation bit correctly, update tile id in header correctly.

1. according to RFC, T bit is only set when either the RTP packet only contains the J2K main header, or the packet contains tile parts from multiple tiles. This is now being managed correctly in the code. The second scenario cannot happen with our payloader, since tile headers are always placed in their own RTP packet, and so a packet cannot contain tile parts from multiple tiles.
However, I have added code to track if multiple tile parts are included in a single RTP packet, in case in the future we want to put header and data in same packet.

2. Old code would set the tile id to zero for all J2K packets. This is now set correctly to the appropriate tile id.

https://bugzilla.gnome.org/show_bug.cgi?id=745187

1 files changed, 35 insertions, 18 deletions

diff --git a/gst/rtp/gstrtpj2kpay.c b/gst/rtp/gstrtpj2kpay.c
index f6c70901b..d30be3152 100644
--- a/gst/rtp/gstrtpj2kpay.c
+++ b/gst/rtp/gstrtpj2kpay.c
@@ -182,8 +182,8 @@ gst_rtp_j2k_pay_scan_marker (const guint8 * data, guint size, guint * offset)
 typedef struct
 {
   RtpJ2KHeader header;
+  gboolean multi_tile_part;
   gboolean bitstream;
-  guint n_tiles;
   guint next_sot;
   gboolean force_packet;
 } RtpJ2KState;
@@ -243,7 +243,7 @@ find_pu_end (GstRtpJ2KPay * pay, const guint8 * data, guint size,
           break;
         case GST_J2K_MARKER_SOT:
         {
-          guint len, Psot;
+          guint len, Psot, tile;
 
           GST_LOG_OBJECT (pay, "found SOT at %u", offset);
           /* SOT for first tile part in code stream:
@@ -262,17 +262,30 @@ find_pu_end (GstRtpJ2KPay * pay, const guint8 * data, guint size,
           if (offset + len >= size)
             return size;
 
-          if (state->n_tiles == 0)
-            /* first tile, T is valid */
+          /* Isot */
+          tile = GST_READ_UINT16_BE (&data[offset + 2]);
+
+          if (!state->multi_tile_part) {
+
+            /* tile is marked as valid */
             state->header.T = 0;
-          else
-            /* more tiles, T becomes invalid */
-            state->header.T = 1;
-          state->header.tile = GST_READ_UINT16_BE (&data[offset + 2]);
-          state->n_tiles++;
 
-          /* get offset of next tile, if it's 0, it goes all the way to the end of
-           * the data */
+            /* we have detected multiple tile parts in this rtp packet : tile bit is now invalid */
+            if (state->header.tile != tile) {
+              state->header.T = 1;
+              state->multi_tile_part = TRUE;
+            }
+          }
+          state->header.tile = tile;
+
+          /* Note: Tile parts from multiple tiles in single RTP packet 
+             will make T invalid.
+             This cannot happen in our case since we always
+             send tile headers in their own RTP packets, so we cannot mix
+             tile parts in a single RTP packet  */
+
+          /* Psot: offset of next tile. If it's 0, next tile goes all the way
+             to the end of the data */
           Psot = GST_READ_UINT32_BE (&data[offset + 4]);
           if (Psot == 0)
             state->next_sot = size;
@@ -286,8 +299,6 @@ find_pu_end (GstRtpJ2KPay * pay, const guint8 * data, guint size,
         }
         case GST_J2K_MARKER_SOD:
           GST_LOG_OBJECT (pay, "found SOD at %u", offset);
-          /* can't have more tiles now */
-          state->n_tiles = 0;
           /* go to bitstream parsing */
           state->bitstream = TRUE;
           /* cut at the next SOP or else include all data */
@@ -342,12 +353,12 @@ gst_rtp_j2k_pay_handle_buffer (GstRTPBasePayload * basepayload,
   state.header.tp = 0;          /* only progressive scan */
   state.header.MHF = 0;         /* no header */
   state.header.mh_id = 0;       /* always 0 for now */
-  state.header.T = 1;           /* invalid tile */
+  state.header.T = 1;           /* invalid tile, because we always begin with the main header */
   state.header.priority = 255;  /* always 255 for now */
-  state.header.tile = 0;        /* no tile number */
+  state.header.tile = -1;       /* no tile number */
   state.header.offset = 0;      /* offset of 0 */
+  state.multi_tile_part = FALSE;
   state.bitstream = FALSE;
-  state.n_tiles = 0;
   state.next_sot = 0;
   state.force_packet = FALSE;
 
@@ -497,13 +508,19 @@ gst_rtp_j2k_pay_handle_buffer (GstRTPBasePayload * basepayload,
 
       gst_buffer_list_add (list, outbuf);
 
-      state.header.T = 1;
-      state.header.tile = 0;
+      /* reset multi_tile */
+      state.multi_tile_part = FALSE;
+
 
       /* set MHF to zero if there is no more main header to process */
       if (state.header.MHF & 2)
         state.header.MHF = 0;
 
+      /* tile is valid, if there is no more header to process */
+      if (!state.header.MHF)
+        state.header.T = 0;
+
+
       offset += data_size;
       state.header.offset = offset;
     }