rtmp: Rewrite embedded flv handling

Use update_offset() as done for rtmp audio, video and notifications and
read update and write the fields instead of replacing them in the rtmp
packet and then memcpying it to the output buffer.

libavformat/rtmpproto.c

@@ -2181,6 +2181,47 @@ static int rtmp_parse_result(URLContext *s, RTMPContext *rt, RTMPPacket *pkt)
     return 0;
 }
 
+static int handle_metadata(RTMPContext *rt, RTMPPacket *pkt)
+{
+    int ret, old_flv_size, type;
+    const uint8_t *next;
+    uint8_t *p;
+    uint32_t size;
+    uint32_t ts, cts, pts = 0;
+
+    old_flv_size = update_offset(rt, pkt->size);
+
+    if ((ret = av_reallocp(&rt->flv_data, rt->flv_size)) < 0)
+        return ret;
+
+    next = pkt->data;
+    p    = rt->flv_data + old_flv_size;
+
+    /* copy data while rewriting timestamps */
+    ts = pkt->timestamp;
+
+    while (next - pkt->data < pkt->size - 11) {
+        type = bytestream_get_byte(&next);
+        size = bytestream_get_be24(&next);
+        cts  = bytestream_get_be24(&next);
+        cts |= bytestream_get_byte(&next) << 24;
+        if (!pts)
+            pts = cts;
+        ts += cts - pts;
+        pts = cts;
+        bytestream_put_byte(&p, type);
+        bytestream_put_be24(&p, size);
+        bytestream_put_be24(&p, ts);
+        bytestream_put_byte(&p, ts >> 24);
+        memcpy(p, next, size + 3 + 4);
+        next += size + 3 + 4;
+        p    += size + 3 + 4;
+    }
+    memcpy(p, next, 11);
+
+    return 0;
+}
+
 /**
  * Interact with the server by receiving and sending RTMP packets until
  * there is some significant data (media data or expected status notification).
@@ -2196,10 +2237,6 @@ static int get_packet(URLContext *s, int for_header)
 {
     RTMPContext *rt = s->priv_data;
     int ret;
-    uint8_t *p;
-    const uint8_t *next;
-    uint32_t size;
-    uint32_t ts, cts, pts=0;
 
     if (rt->state == STATE_STOPPED)
         return AVERROR_EOF;
@@ -2266,30 +2303,7 @@ static int get_packet(URLContext *s, int for_header)
             ff_rtmp_packet_destroy(&rpkt);
             return ret;
         } else if (rpkt.type == RTMP_PT_METADATA) {
-            int err;
-            // we got raw FLV data, make it available for FLV demuxer
-            rt->flv_off  = 0;
-            rt->flv_size = rpkt.size;
-            if ((err = av_reallocp(&rt->flv_data, rt->flv_size)) < 0)
-                return err;
-            /* rewrite timestamps */
-            next = rpkt.data;
-            ts = rpkt.timestamp;
-            while (next - rpkt.data < rpkt.size - 11) {
-                next++;
-                size = bytestream_get_be24(&next);
-                p=next;
-                cts = bytestream_get_be24(&next);
-                cts |= bytestream_get_byte(&next) << 24;
-                if (pts==0)
-                    pts=cts;
-                ts += cts - pts;
-                pts = cts;
-                bytestream_put_be24(&p, ts);
-                bytestream_put_byte(&p, ts >> 24);
-                next += size + 3 + 4;
-            }
-            memcpy(rt->flv_data, rpkt.data, rpkt.size);
+            ret = handle_metadata(rt, &rpkt);
             ff_rtmp_packet_destroy(&rpkt);
             return 0;
         }