[FFmpeg-devel] [PATCH] avformat/webvttdec: Fix WebVTT decoder truncating files at first STYLE block

[Dave Evans]

Hijacking with related, similar patch from a few months ago:
https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=2538


On Tue, Jan 12, 2021 at 4:56 PM Roderich Schupp <roderich.schupp at gmail.com>
wrote:

> Bug-ID: 9064
>
> The webvtt decoder truncates the file at the first such block.
> Since these blocks typically occur at the top of the webvtt file, this
> results
> in an empty file (except for the WEBVTT header line).
>
> Reason is that at STYLE block neither parses as a valid cue block nor
> is it skipped like the WEBVTT (i.e. header) or NOTE blocks, hence
> decoding stops.
>
> Solution is to add STYLE to list of skipped blocks. And while we're at it,
> add REGION, too.
> ---
>  libavformat/webvttdec.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/webvttdec.c b/libavformat/webvttdec.c
> index 8d2fdfe..5a982dd 100644
> --- a/libavformat/webvttdec.c
> +++ b/libavformat/webvttdec.c
> @@ -89,10 +89,12 @@ static int webvtt_read_header(AVFormatContext *s)
>          p = identifier = cue.str;
>          pos = avio_tell(s->pb);
>
> -        /* ignore header chunk */
> +        /* ignore header, NOTE, STYLE and REGION chunks */
>          if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
>              !strncmp(p, "WEBVTT", 6) ||
> -            !strncmp(p, "NOTE", 4))
> +            !strncmp(p, "NOTE", 4) ||
> +            !strncmp(p, "STYLE", 5) ||
> +            !strncmp(p, "REGION", 6))
>              continue;
>
>          /* optional cue identifier (can be a number like in SRT or some
> kind of
> --
> 2.30.0
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".