[FFmpeg-devel] [PATCH] avformat/dhav: Fix incorrect non-DHAV chunk skipping logic

[Idan Freiberg]

Can one of the maintainers review the patch please?

בתאריך יום ד׳, 13 בינו׳ 2021 ב-14:35 מאת Idan Freiberg <speidy at gmail.com>:

> DAV files may contain a variable length padding in between chunks
> filled with 0xff bytes. The current skipping logic is incorrect as it
> may skip over DHAV chunks not appearing sequentially in the file.
>
> We now look for the 'DHAV' tag using a byte-by-byte search in order
> to handle such situations. Also the dhav->last_good_pos field will
> not be updated while skipping unrecognized data.
> ---
>  libavformat/dhav.c | 15 +++------------
>  1 file changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/libavformat/dhav.c b/libavformat/dhav.c
> index 00e0d8476e..6a6c235e65 100644
> --- a/libavformat/dhav.c
> +++ b/libavformat/dhav.c
> @@ -173,18 +173,9 @@ static int read_chunk(AVFormatContext *s)
>      if (avio_feof(s->pb))
>          return AVERROR_EOF;
>
> -    if (avio_rl32(s->pb) != MKTAG('D','H','A','V') && dhav->last_good_pos
> < INT64_MAX - 0x8000) {
> -        dhav->last_good_pos += 0x8000;
> -        avio_seek(s->pb, dhav->last_good_pos, SEEK_SET);
> -
> -        while (avio_rl32(s->pb) != MKTAG('D','H','A','V')) {
> -            if (avio_feof(s->pb) || dhav->last_good_pos >= INT64_MAX -
> 0x8000)
> -                return AVERROR_EOF;
> -            dhav->last_good_pos += 0x8000;
> -            ret = avio_skip(s->pb, 0x8000 - 4);
> -            if (ret < 0)
> -                return ret;
> -        }
> +    while (avio_r8(s->pb) != 'D' || avio_r8(s->pb) != 'H' ||
> avio_r8(s->pb) != 'A' || avio_r8(s->pb) != 'V') {
> +        if (avio_feof(s->pb))
> +            return AVERROR_EOF;
>      }
>
>      start = avio_tell(s->pb) - 4;
> --
> 2.30.0
>
> --
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