[FFmpeg-cvslog] png: Clear up the calculation of max packet size

[Donny Yang]

ffmpeg | branch: master | Donny Yang <work at kota.moe> | Tue Mar 31 12:37:22 2015 +0000| [749fbfd0817528aa4f43339ce1a3d92f0a258a45] | committer: Michael Niedermayer

png: Clear up the calculation of max packet size

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=749fbfd0817528aa4f43339ce1a3d92f0a258a45
---

 libavcodec/pngenc.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libavcodec/pngenc.c b/libavcodec/pngenc.c
index 8fff0f3..c913cce 100644
--- a/libavcodec/pngenc.c
+++ b/libavcodec/pngenc.c
@@ -307,12 +307,16 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     row_size       = (avctx->width * s->bits_per_pixel + 7) >> 3;
 
     enc_row_size    = deflateBound(&s->zstream, row_size);
-    max_packet_size = avctx->height * (int64_t)(enc_row_size +
-                                       ((enc_row_size + IOBUF_SIZE - 1) / IOBUF_SIZE) * 12)
-                      + FF_MIN_BUFFER_SIZE;
+    max_packet_size =
+        FF_MIN_BUFFER_SIZE + // headers
+        avctx->height * (
+            enc_row_size +
+            12 * (((int64_t)enc_row_size + IOBUF_SIZE - 1) / IOBUF_SIZE) // IDAT * ceil(enc_row_size / IOBUF_SIZE)
+        );
     if (max_packet_size > INT_MAX)
         return AVERROR(ENOMEM);
-    if ((ret = ff_alloc_packet2(avctx, pkt, max_packet_size)) < 0)
+    ret = ff_alloc_packet2(avctx, pkt, max_packet_size);
+    if (ret < 0)
         return ret;
 
     s->bytestream_start =