[FFmpeg-devel] [PATCH v2] avformat/hlsenc: Respect `append_list` flag in subtitle playlists

[Steven Liu]

Jonathan Baecker <jonbae77 at gmail.com> 于2024年9月29日周日 03:51写道：
Hi Jonathan,

>
> Ensure that when the `-hls_flags append_list` option is set,
> that *.vtt files in stream_vtt.m3u8 are correctly updated.
>
> This fixes https://trac.ffmpeg.org/ticket/11208
>
> Is a bit of an ugly fix, let me know what you think.
> ---
>  libavformat/hlsenc.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index 1e932b7..e93af4c 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -1202,6 +1202,22 @@ static int hls_append_segment(struct AVFormatContext *s, HLSContext *hls,
>      return 0;
>  }
>
> +static int extract_number(const char *filename) {
> +    const char *dot = strrchr(filename, '.');
> +    const char *num_start = dot - 1;
> +
> +    while (num_start > filename && *num_start >= '0' && *num_start <= '9') {
> +        num_start--;
> +    }
> +
> +    num_start++;
> +
> +    if (num_start == dot)
> +        return -1;
> +
> +    return atoi(num_start);
> +}
> +
>  static int parse_playlist(AVFormatContext *s, const char *url, VariantStream *vs)
>  {
>      HLSContext *hls = s->priv_data;
> @@ -1294,6 +1310,27 @@ static int parse_playlist(AVFormatContext *s, const char *url, VariantStream *vs
>                      ret = AVERROR(ENOMEM);
>                      goto fail;
>                  }
> +                if (vs->has_subtitle) {
> +                    int vtt_index = extract_number(line);
> +                    char *vtt_file = av_asprintf(av_basename(vs->vtt_basename), vtt_index);

Possible security issue, make sure this is safe or use snprintf/av_strl*
/Users/StevenLiu/FFmpeg-devel-v2-avformat-hlsenc-Respect-append_list-flag-in-subtitle-playlists.patch:180:+
                   char *vtt_file =
av_asprintf(av_basename(vs->vtt_basename), vtt_index);

> +                    char *new_vtt;
> +
> +                    if (!vtt_file) {
> +                        ret = AVERROR(ENOMEM);
> +                        goto fail;
> +                    }
> +
> +                    new_vtt = av_strdup(vtt_file);
> +                    av_free(vtt_file);
> +
> +                    if (!new_vtt) {
> +                        ret = AVERROR(ENOMEM);
> +                        goto fail;
> +                    }
> +
> +                    ff_format_set_url(vs->vtt_avf, new_vtt);
> +                }
> +
>                  ff_format_set_url(vs->avf, new_file);
Maybe this line should move above the "if (vs->has_subtitle) {" block,
because there have new_file need process if (!new_vtt) {.
So if you move ff_format_set_url(vs->avf, new_file); to above vtt
process logic, it should be release by vs->avf default logic.
It it right?

 >                  is_segment = 0;
>                  new_start_pos = avio_tell(vs->avf->pb);
> --
> 2.46.1
>
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Thanks