[FFmpeg-devel] [PATCH] lavfi/subtitles: load attached fonts to libass.

[wm4]

On Tue, 8 Apr 2014 14:42:52 +0200
Clément Bœsch <u at pkh.me> wrote:

> On Mon, Apr 07, 2014 at 11:35:01PM -0300, Facundo Gaich wrote:
> > Videos with complex typesetting usually have font files embedded
> > as attachment streams. vf_subtitles now finds all attachment
> > streams with a MIME type associated with fonts and loads them
> > to libass so it can use them for rendering.
> > 
> > The code was basically ported from mpv's loadfile.c at 929793be7
> > 
> > Signed-off-by: Facundo Gaich <facugaich at gmail.com>
> > ---
> >  libavfilter/vf_subtitles.c | 53 +++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 52 insertions(+), 1 deletion(-)
> > 
> > diff --git a/libavfilter/vf_subtitles.c b/libavfilter/vf_subtitles.c
> > index e44f61d..8586304 100644
> > --- a/libavfilter/vf_subtitles.c
> > +++ b/libavfilter/vf_subtitles.c
> > @@ -249,11 +249,34 @@ static const AVOption subtitles_options[] = {
> >      {NULL},
> >  };
> >  
> > +static const char *font_mimetypes[] = {
> > +    "application/x-truetype-font",
> > +    "application/vnd.ms-opentype",
> > +    "application/x-font-ttf",
> > +    "application/x-font",
> > +    NULL

Looks exactly like the font mime type list in mpv. Note that
'application/x-font' probably never existed officially (e.g. it's not
in Haali's matroska demuxer), and is probably wrong. On the other hand,
it's probably not harmful to have this entry.

> > +};
> > +
> > +static int attachment_is_font(AVStream * st)
> > +{
> > +    const AVDictionaryEntry *tag = NULL;
> > +
> > +    tag = av_dict_get(st->metadata, "mimetype", NULL, AV_DICT_MATCH_CASE);
> > +
> > +    if (tag) {
> > +        for (int n = 0; font_mimetypes[n]; n++) {
> 
> int should be out of the loop (it's not supported by all the compilers
> FFmpeg supports).
> 
> > +            if (strcmp(font_mimetypes[n], tag->value) == 0)

I think mime types are usually not case sensitive, so this catches
fonts with lowercase mime types only.

> > +                return 1;
> > +        }
> > +    }
> > +    return 0;
> > +}
> > +
> >  AVFILTER_DEFINE_CLASS(subtitles);
> >  
> >  static av_cold int init_subtitles(AVFilterContext *ctx)
> >  {
> > -    int ret, sid;
> > +    int ret, sid, loaded_fonts;
> >      AVDictionary *codec_opts = NULL;
> >      AVFormatContext *fmt = NULL;
> >      AVCodecContext *dec_ctx = NULL;
> > @@ -293,6 +316,34 @@ static av_cold int init_subtitles(AVFilterContext *ctx)
> >      sid = ret;
> >      st = fmt->streams[sid];
> >  
> > +    /* Load attached fonts */
> > +    for (int j = 0; j < fmt->nb_streams; j++) {
> 
> ditto
> 
> > +        AVStream *st = fmt->streams[j];
> > +        if ((st->codec->codec_type == AVMEDIA_TYPE_ATTACHMENT) &&
> 
> Extra parenthesis
> 
> > +            attachment_is_font(st)) {
> > +            const AVDictionaryEntry *tag = NULL;
> > +            tag = av_dict_get(st->metadata, "filename", NULL,
> > +                              AV_DICT_MATCH_CASE);
> > +
> > +            if (tag) {
> > +                av_log(ctx, AV_LOG_DEBUG, "Loading attached font: %s\n",
> > +                       tag->value);
> > +                ass_add_font(ass->library, tag->value,
> > +                             st->codec->extradata,
> > +                             st->codec->extradata_size);
> > +                loaded_fonts = 1;
> > +            } else {
> > +                av_log(ctx, AV_LOG_WARNING,
> > +                       "Font attachment has no filename, ignored.\n");
> > +            }
> > +        }
> > +    }
> > +    if (loaded_fonts) {
> > +        /* Ideally this would be ass_fonts_update, but it seems to be broken
> > +         * as of libass 0.11.1 */
> 
> Can you add a bug id or something for reference in the comment?

IMO not really a bug. ass_fonts_update() literally just calls
FcConfigBuildFonts, i.e. it updates the system fonts.
ass_set_fonts on the other hand adds fonts from ASS_Library to
ASS_Renderer.

(It's worth noticing that libass wants to remove the separation between
ASS_Library and ASS_Renderer, so the need for the API call will
probably be removed once that is done.)

> > +        ass_set_fonts(ass->renderer, NULL, NULL, 1, NULL, 1);
> > +    }
> > +
> >      /* Open decoder */
> >      dec_ctx = st->codec;
> >      dec = avcodec_find_decoder(dec_ctx->codec_id);
> 
> Otherwise it looks OK.
>