rtmp: Support reading interleaved chunks.

A given packet won't always come in contiguously; sometimes
they may be broken up on chunk boundaries by packets of another
channel.

This support primarily involves tracking information about the
data that's been read, so the reader can pick up where it left
off for a given channel.

As a side effect, we no longer over-report the bytes read if
(toread = MIN(size, chunk_size)) == size

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtmppkt.c

@@ -140,16 +140,17 @@ int ff_rtmp_packet_read(URLContext *h, RTMPPacket *p,
     return ff_rtmp_packet_read_internal(h, p, chunk_size, prev_pkt, hdr);
 }
 
-int ff_rtmp_packet_read_internal(URLContext *h, RTMPPacket *p, int chunk_size,
-                                 RTMPPacket *prev_pkt, uint8_t hdr)
+static int rtmp_packet_read_one_chunk(URLContext *h, RTMPPacket *p,
+                                      int chunk_size, RTMPPacket *prev_pkt,
+                                      uint8_t hdr)
 {
 
-    uint8_t t, buf[16];
-    int channel_id, timestamp, size, offset = 0;
+    uint8_t buf[16];
+    int channel_id, timestamp, size;
     uint32_t extra = 0;
     enum RTMPPacketType type;
     int written = 0;
-    int ret;
+    int ret, toread;
 
     written++;
     channel_id = hdr & 0x3F;
@@ -198,37 +199,69 @@ int ff_rtmp_packet_read_internal(URLContext *h, RTMPPacket *p, int chunk_size,
     if (hdr != RTMP_PS_TWELVEBYTES)
         timestamp += prev_pkt[channel_id].timestamp;
 
-    if ((ret = ff_rtmp_packet_create(p, channel_id, type, timestamp,
-                                     size)) < 0)
-        return ret;
+    if (!prev_pkt[channel_id].read) {
+        if ((ret = ff_rtmp_packet_create(p, channel_id, type, timestamp,
+                                         size)) < 0)
+            return ret;
+        p->read = written;
+        p->offset = 0;
+        prev_pkt[channel_id].ts_delta   = timestamp -
+                                          prev_pkt[channel_id].timestamp;
+        prev_pkt[channel_id].timestamp  = timestamp;
+    } else {
+        // previous packet in this channel hasn't completed reading
+        RTMPPacket *prev = &prev_pkt[channel_id];
+        p->data          = prev->data;
+        p->size          = prev->size;
+        p->channel_id    = prev->channel_id;
+        p->type          = prev->type;
+        p->ts_delta      = prev->ts_delta;
+        p->extra         = prev->extra;
+        p->offset        = prev->offset;
+        p->read          = prev->read + written;
+        p->timestamp     = prev->timestamp;
+        prev->data       = NULL;
+    }
     p->extra = extra;
     // save history
     prev_pkt[channel_id].channel_id = channel_id;
     prev_pkt[channel_id].type       = type;
     prev_pkt[channel_id].size       = size;
-    prev_pkt[channel_id].ts_delta   = timestamp - prev_pkt[channel_id].timestamp;
-    prev_pkt[channel_id].timestamp  = timestamp;
     prev_pkt[channel_id].extra      = extra;
-    while (size > 0) {
-        int toread = FFMIN(size, chunk_size);
-        if (ffurl_read_complete(h, p->data + offset, toread) != toread) {
-            ff_rtmp_packet_destroy(p);
+    size = size - p->offset;
+
+    toread = FFMIN(size, chunk_size);
+    if (ffurl_read_complete(h, p->data + p->offset, toread) != toread) {
+        ff_rtmp_packet_destroy(p);
+        return AVERROR(EIO);
+    }
+    size      -= toread;
+    p->read   += toread;
+    p->offset += toread;
+
+    if (size > 0) {
+       RTMPPacket *prev = &prev_pkt[channel_id];
+       prev->data = p->data;
+       prev->read = p->read;
+       prev->offset = p->offset;
+       return AVERROR(EAGAIN);
+    }
+
+    prev_pkt[channel_id].read = 0; // read complete; reset if needed
+    return p->read;
+}
+
+int ff_rtmp_packet_read_internal(URLContext *h, RTMPPacket *p, int chunk_size,
+                                 RTMPPacket *prev_pkt, uint8_t hdr)
+{
+    while (1) {
+        int ret = rtmp_packet_read_one_chunk(h, p, chunk_size, prev_pkt, hdr);
+        if (ret > 0 || ret != AVERROR(EAGAIN))
+            return ret;
+
+        if (ffurl_read(h, &hdr, 1) != 1)
             return AVERROR(EIO);
-        }
-        size    -= chunk_size;
-        offset  += chunk_size;
-        written += chunk_size;
-        if (size > 0) {
-            if ((ret = ffurl_read_complete(h, &t, 1)) < 0) { // marker
-                ff_rtmp_packet_destroy(p);
-                return ret;
-            }
-            written++;
-            if (t != (0xC0 + channel_id))
-                return -1;
-        }
     }
-    return written;
 }
 
 int ff_rtmp_packet_write(URLContext *h, RTMPPacket *pkt,

libavformat/rtmppkt.h

@@ -82,6 +82,8 @@ typedef struct RTMPPacket {
     uint32_t       extra;      ///< probably an additional channel ID used during streaming data
     uint8_t        *data;      ///< packet payload
     int            size;       ///< packet payload size
+    int            offset;     ///< amount of data read so far
+    int            read;       ///< amount read, including headers
 } RTMPPacket;
 
 /**

libavformat/rtmpproto.c

@@ -2309,7 +2309,7 @@ static int get_packet(URLContext *s, int for_header)
 static int rtmp_close(URLContext *h)
 {
     RTMPContext *rt = h->priv_data;
-    int ret = 0;
+    int ret = 0, i, j;
 
     if (!rt->is_input) {
         rt->flv_data = NULL;
@@ -2320,6 +2320,9 @@ static int rtmp_close(URLContext *h)
     }
     if (rt->state > STATE_HANDSHAKED)
         ret = gen_delete_stream(h, rt);
+    for (i = 0; i < 2; i++)
+        for (j = 0; j < RTMP_CHANNELS; j++)
+            ff_rtmp_packet_destroy(&rt->prev_pkt[i][j]);
 
     free_tracked_methods(rt);
     av_freep(&rt->flv_data);