[FFmpeg-devel] matroskadec: support S_TEXT/WEBVTT

[Wang Bin]

Leo Izen <leo.izen at gmail.com> 于2024年12月26日周四 00:45写道：

> On 12/25/24 3:46 AM, Wang Bin wrote:
> > On 12/19/24 3:59 AM, Wang Bin wrote:
> >>> based on Hendrik Leppkes's fork
> >>>
> >>>
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> >>>
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> >>
> >> This patch has a big web of gotos. This can get very confusing. Is there
> >> any way to change it so there's if blocks or other static functions to
> >> call? Gotos should be used very sparingly and mostly to goto the end of
> >> a block where cleanup happens.
> >>
> >> - Leo Izen (Traneptora)
>
>
> > From 5bd4a6f56231c3160be6c2d322f5d1081d7b3622 Mon Sep 17 00:00:00 2001
> > From: wang-bin <wbsecg1 at gmail.com>
> > Date: Tue, 17 Dec 2024 23:21:57 +0800
> > Subject: [PATCH] matroskadec: support S_TEXT/WEBVTT
> >
> > fix ticket #5641
> > ---
> >   libavformat/matroska.c    |   1 +
> >   libavformat/matroskadec.c | 102 ++++++++++++++++++++++----------------
> >   2 files changed, 60 insertions(+), 43 deletions(-)
> >
> > diff --git a/libavformat/matroska.c b/libavformat/matroska.c
> > index d0ecfbeb6a..23c4ad6949 100644
> > --- a/libavformat/matroska.c
> > +++ b/libavformat/matroska.c
> > @@ -63,6 +63,7 @@ const CodecTags ff_mkv_codec_tags[]={
> >       {"D_WEBVTT/CAPTIONS"    , AV_CODEC_ID_WEBVTT},
> >       {"D_WEBVTT/DESCRIPTIONS", AV_CODEC_ID_WEBVTT},
> >       {"D_WEBVTT/METADATA"    , AV_CODEC_ID_WEBVTT},
> > +    {"S_TEXT/WEBVTT"        , AV_CODEC_ID_WEBVTT},
> >
> >       {"S_TEXT/UTF8"      , AV_CODEC_ID_SUBRIP},
> >       {"S_TEXT/UTF8"      , AV_CODEC_ID_TEXT},
> > diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> > index 0e150f9138..11af2cface 100644
> > --- a/libavformat/matroskadec.c
> > +++ b/libavformat/matroskadec.c
> > @@ -3761,68 +3761,83 @@ static int matroska_parse_prores(MatroskaTrack
> > *track,
> >       return 0;
> >   }
> >
> > +static int matroska_webvtt_read_line(uint8_t** begin, uint8_t* end)
>
> static ptrdiff_t matroska_webvtt_read_line(const uint8_t **begin, const
> uint8_t *end)
>
> > +{
> > +    uint8_t *p = *begin;
> > +    int len = -1;
>
> ptrdiff_t len = -1;
>
>
> > +
> > +    while (p < end) {
> > +        if (*p == '\r' || *p == '\n') {
> > +            len = p - *begin;
> > +            if (*p == '\r')
> > +                p++;
>
> This will cause AVERROR_INVALIDDATA to return, if a \r is found without
> a \n after it. Is this intentional?
>
>
Not sure. Copied from existing code.


> > +            break;
> > +        }
> > +        p++;
> > +    }
> > +
> > +    if (p >= end || *p != '\n')
> > +        return AVERROR_INVALIDDATA;
> > +    p++;
> > +    *begin = p;
>
>
> These two lines can be replaced with: *begin = p + 1;
>
>
>
> > +    return len;
> > +}
> > +
> >   static int matroska_parse_webvtt(MatroskaDemuxContext *matroska,
> >                                    MatroskaTrack *track,
> >                                    AVStream *st,
> >                                    uint8_t *data, int data_len,
> > +                                 MatroskaBlockMore *blockmore, int
> > nb_blockmore,
> >                                    uint64_t timecode,
> >                                    uint64_t duration,
> >                                    int64_t pos)
> >   {
> >       AVPacket *pkt = matroska->pkt;
> >       uint8_t *id, *settings, *text, *buf;
> > -    int id_len, settings_len, text_len;
> > +    int id_len = -1, settings_len = -1, text_len = -1;
>
> ptrdiff_t id_len, settings_le, text_len;
>
> This are never read uninitialized.
>
>
No, if !webm_style && nb_blockmore == 0, id_len and settings_len won't
change
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