Re: [FFmpeg-devel] [PATCH] Signed-off-by: devjeonghwan <dev.parkjeonghwan@gmail.com>

[박정환 <dev.parkjeonghwan@gmail.com>]

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.parkjeonghwan@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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