Parse dri when receiving jpg via rtp.

Based on a patch by contact at iridiummobile ru.
Fixes ticket #3780.

libavformat/rtpdec_jpeg.c

@@ -106,7 +106,8 @@ static void jpeg_put_marker(PutByteContext *pbc, int code)
 }
 
 static int jpeg_create_header(uint8_t *buf, int size, uint32_t type, uint32_t w,
-                              uint32_t h, const uint8_t *qtable, int nb_qtable)
+                              uint32_t h, const uint8_t *qtable, int nb_qtable,
+                              int dri)
 {
     PutByteContext pbc;
     uint8_t *dht_size_ptr;
@@ -132,6 +133,12 @@ static int jpeg_create_header(uint8_t *buf, int size, uint32_t type, uint32_t w,
     bytestream2_put_byte(&pbc, 0);
     bytestream2_put_byte(&pbc, 0);
 
+    if (dri) {
+        jpeg_put_marker(&pbc, DRI);
+        bytestream2_put_be16(&pbc, 4);
+        bytestream2_put_be16(&pbc, dri);
+    }
+
     /* DQT */
     jpeg_put_marker(&pbc, DQT);
     bytestream2_put_be16(&pbc, 2 + nb_qtable * (1 + 64));
@@ -226,7 +233,7 @@ static int jpeg_parse_packet(AVFormatContext *ctx, PayloadContext *jpeg,
     const uint8_t *qtables = NULL;
     uint16_t qtable_len;
     uint32_t off;
-    int ret;
+    int ret, dri = 0;
 
     if (len < 8) {
         av_log(ctx, AV_LOG_ERROR, "Too short RTP/JPEG packet.\n");
@@ -242,6 +249,16 @@ static int jpeg_parse_packet(AVFormatContext *ctx, PayloadContext *jpeg,
     buf += 8;
     len -= 8;
 
+    if (type & 0x40) {
+        if (len < 4) {
+            av_log(ctx, AV_LOG_ERROR, "Too short RTP/JPEG packet.\n");
+            return AVERROR_INVALIDDATA;
+        }
+        dri = AV_RB16(buf);
+        buf += 4;
+        len -= 4;
+        type &= ~0x40;
+    }
     /* Parse the restart marker header. */
     if (type > 63) {
         av_log(ctx, AV_LOG_ERROR,
@@ -332,7 +349,7 @@ static int jpeg_parse_packet(AVFormatContext *ctx, PayloadContext *jpeg,
          * interchange format. */
         jpeg->hdr_size = jpeg_create_header(hdr, sizeof(hdr), type, width,
                                             height, qtables,
-                                            qtable_len / 64);
+                                            qtable_len / 64, dri);
 
         /* Copy JPEG header to frame buffer. */
         avio_write(jpeg->frame, hdr, jpeg->hdr_size);