apngdec: use side data to pass extradata to the decoder

Fixes remuxing apng streams coming from the apng demuxer.
This is a regression since 940b8908b94404a65f9f55e33efb4ccc6c81383c.

Found-by: James Almer <jamrial@gmail.com>
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 36275ae43f..83eeb8d322 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -45,6 +45,9 @@ typedef struct PNGDecContext {
     ThreadFrame last_picture;
     ThreadFrame picture;
 
+    uint8_t* extra_data;
+    int extra_data_size;
+
     int state;
     int width, height;
     int cur_w, cur_h;
@@ -1361,14 +1364,28 @@ static int decode_frame_apng(AVCodecContext *avctx,
     p = s->picture.f;
 
     if (!(s->state & PNG_IHDR)) {
-        if (!avctx->extradata_size)
+        int side_data_size = 0;
+        uint8_t *side_data = NULL;
+        if (avpkt)
+            side_data = av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);
+
+        if (side_data_size) {
+            av_freep(&s->extra_data);
+            s->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
+            if (!s->extra_data)
+                return AVERROR(ENOMEM);
+            s->extra_data_size = side_data_size;
+            memcpy(s->extra_data, side_data, s->extra_data_size);
+        }
+
+        if (!s->extra_data_size)
             return AVERROR_INVALIDDATA;
 
         /* only init fields, there is no zlib use in extradata */
         s->zstream.zalloc = ff_png_zalloc;
         s->zstream.zfree  = ff_png_zfree;
 
-        bytestream2_init(&s->gb, avctx->extradata, avctx->extradata_size);
+        bytestream2_init(&s->gb, s->extra_data, s->extra_data_size);
         if ((ret = decode_frame_common(avctx, s, p, avpkt)) < 0)
             goto end;
     }
@@ -1494,6 +1511,8 @@ static av_cold int png_dec_end(AVCodecContext *avctx)
     s->last_row_size = 0;
     av_freep(&s->tmp_row);
     s->tmp_row_size = 0;
+    av_freep(&s->extra_data);
+    s->extra_data_size = 0;
 
     return 0;
 }