From 9e1cfbd38a18f8ed8ba5ba1f7d21c73a8162ba19 Mon Sep 17 00:00:00 2001
From: Benoit Fouet <benoit.fouet@free.fr>
Date: Mon, 24 Nov 2014 16:12:26 +0100
Subject: [PATCH] avformat/apngdec: transmit all the chunks between consecutive
 fcTL ones.

In order to support multiple IDAT of fdAT chunks following an fcTL one,
transmit all the chunks between two fcTL ones (or between fcTL and IEND
one).

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
---
 libavformat/apngdec.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/libavformat/apngdec.c b/libavformat/apngdec.c
index 1e0f1c7c13..d766a87105 100644
--- a/libavformat/apngdec.c
+++ b/libavformat/apngdec.c
@@ -24,10 +24,6 @@
  * APNG demuxer.
  * @see https://wiki.mozilla.org/APNG_Specification
  * @see http://www.w3.org/TR/PNG
- *
- * Not supported (yet):
- *     - streams with chunks other than fcTL / fdAT / IEND after the first fcTL
- *     - streams with multiple fdAT chunks after an fcTL one
  */
 
 #include "avformat.h"
@@ -325,8 +321,6 @@ static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)
      * and needed next:
      *  4 (length)
      *  4 (tag (must be fdAT or IDAT))
-     *
-     *  TODO: support multiple fdAT following an fcTL
      */
     /* if num_play is not 1, then the seekback is already guaranteed */
     if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 46)) < 0)
@@ -350,15 +344,35 @@ static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)
             tag != MKTAG('I', 'D', 'A', 'T'))
             return AVERROR_INVALIDDATA;
 
-        if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0)
-            return ret;
-
         size = 38 /* fcTL */ + 8 /* len, tag */ + len + 4 /* crc */;
         if (size > INT_MAX)
             return AVERROR(EINVAL);
 
-        if ((ret = av_get_packet(pb, pkt, size)) < 0)
+        if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0 ||
+            (ret = av_append_packet(pb, pkt, size)) < 0)
             return ret;
+
+        if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
+            return ret;
+
+        len = avio_rb32(pb);
+        tag = avio_rl32(pb);
+        while (tag &&
+               tag != MKTAG('f', 'c', 'T', 'L') &&
+               tag != MKTAG('I', 'E', 'N', 'D')) {
+            if (len > 0x7fffffff)
+                return AVERROR_INVALIDDATA;
+            if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
+                (ret = av_append_packet(pb, pkt, len + 12)) < 0)
+                return ret;
+            if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
+                return ret;
+            len = avio_rb32(pb);
+            tag = avio_rl32(pb);
+        }
+        if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
+            return ret;
+
         if (ctx->is_key_frame)
             pkt->flags |= AV_PKT_FLAG_KEY;
         return ret;