Please ignore this patch due to incorrect patch subject format.
The correct patch to review is:
"[FFmpeg-devel] avformat/apngdec: allow other chunks between fcTL and
fdAT/IDAT"
Sorry for the confusion.
2025년 8월 4일 (월) 오후 3:32, devjeonghwan <dev.parkjeongh...@gmail.com>님이 작성:
> avformat/apngdec: allow other chunks between fcTL and fdAT/IDAT
>
> The APNG demuxer incorrectly assumed that fcTL chunks must be
> immediately followed by fdAT or IDAT chunks. Per PNG specification
> section 14.3.2, ancillary chunks may appear in any order relative
> to other ancillary chunks.
>
> This change allows intermediate chunks (like tEXt) between fcTL
> and frame data chunks, fixing playback of APNG files with metadata.
>
> Fixes #11012.
> ---
> libavformat/apngdec.c | 21 +++++++++++++++++----
> 1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/apngdec.c b/libavformat/apngdec.c
> index d0005046c1..a21878b246 100644
> --- a/libavformat/apngdec.c
> +++ b/libavformat/apngdec.c
> @@ -344,14 +344,27 @@ static int apng_read_packet(AVFormatContext *s,
> AVPacket *pkt)
> if ((ret = decode_fctl_chunk(s, ctx, pkt)) < 0)
> return ret;
>
> - /* fcTL must precede fdAT or IDAT */
> + /* fcTL may be followed by other chunks before fdAT or IDAT */
> len = avio_rb32(pb);
> tag = avio_rl32(pb);
> - if (len > 0x7fffffff ||
> - tag != MKTAG('f', 'd', 'A', 'T') &&
> - tag != MKTAG('I', 'D', 'A', 'T'))
> + if (len > 0x7fffffff)
> return AVERROR_INVALIDDATA;
>
> + /* check for empty frame */
> + if (tag == MKTAG('f', 'c', 'T', 'L') ||
> + tag == MKTAG('I', 'E', 'N', 'D')) {
> + size = 38; /* size of fcTL chunk and its header */
> + if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0 ||
> + (ret = av_append_packet(pb, pkt, size)) < 0)
> + return ret;
> +
> + if (ctx->is_key_frame)
> + pkt->flags |= AV_PKT_FLAG_KEY;
> + pkt->pts = pkt->dts = AV_NOPTS_VALUE;
> + pkt->duration = ctx->pkt_duration;
> + return ret;
> + }
> +
> size = 38 /* fcTL */ + 8 /* len, tag */ + len + 4 /* crc */;
> if (size > INT_MAX)
> return AVERROR(EINVAL);
> --
> 2.34.1
>
>
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