On Mon, May 18, 2020 at 11:34:03AM +0200, Manolis Stamatogiannakis wrote:
> Bumping this up after 10 days without a comment.
>
> On Fri, 8 May 2020 at 13:14, Manolis Stamatogiannakis <msta...@gmail.com>
> wrote:
>
> > Allows shifting of subtitle display times to align them with the video.
> > This avoids having to rewrite the subtitle file in order to display
> > subtitles correctly when input is seeked (-ss).
> > Also handy for minor subtitle timing corrections without rewriting the
> > subtitles file.
> >
> > Signed-off-by: Manolis Stamatogiannakis <msta...@gmail.com>
> > ---
> > doc/filters.texi | 8 ++++++++
> > libavfilter/vf_subtitles.c | 29 +++++++++++++++++++++++++++--
> > 2 files changed, 35 insertions(+), 2 deletions(-)
> >
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index d19fd346ae..94323495f0 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -17851,6 +17851,9 @@ The filter accepts the following options:
> > @item filename, f
> > Set the filename of the subtitle file to read. It must be specified.
> >
> > +@item shift
> > +Shift subtitles timings by the specified amount.
> > +
> > @item original_size
> > Specify the size of the original video, the video for which the ASS file
> > was composed. For the syntax of this option, check the
> > @@ -17907,6 +17910,11 @@ To make the subtitles stream from @file{sub.srt}
> > appear in 80% transparent blue
> > subtitles=sub.srt:force_style='FontName=DejaVu
> > Serif,PrimaryColour=&HCCFF0000'
> > @end example
> >
> > +To re-sync subtitles after seeking the input e.g. with @code{-ss 20:20},
> > use:
> > +@example
> > +subtitles=filename=sub.srt:shift=-20\:20
> > +@end example
> > +
> > @section super2xsai
> >
> > Scale the input by 2x and smooth using the Super2xSaI (Scale and
> > diff --git a/libavfilter/vf_subtitles.c b/libavfilter/vf_subtitles.c
> > index a3b4029af4..47a38b55b1 100644
> > --- a/libavfilter/vf_subtitles.c
> > +++ b/libavfilter/vf_subtitles.c
> > @@ -52,6 +52,8 @@ typedef struct AssContext {
> > char *filename;
> > char *fontsdir;
> > char *charenc;
> > + int64_t shift;
> > + char *shift_opt;
> > char *force_style;
> > int stream_index;
> > int alpha;
> > @@ -68,6 +70,7 @@ typedef struct AssContext {
> > #define COMMON_OPTIONS \
> > {"filename", "set the filename of file to read",
> > OFFSET(filename), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0,
> > FLAGS }, \
> > {"f", "set the filename of file to read",
> > OFFSET(filename), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0,
> > FLAGS }, \
> > + {"shift", "shift the timing of the subtitles",
> > OFFSET(shift_opt), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0,
> > FLAGS }, \
I can't give comments for the function, but here It's better to use
AV_OPT_TYPE_DURATION type
for the timing shift, then you can use shift directly and shift_opt isn't
necessary anymore.
> > {"original_size", "set the size of the original video (used to scale
> > fonts)", OFFSET(original_w), AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL}, 0, 0,
> > FLAGS }, \
> > {"fontsdir", "set the directory containing the fonts to read",
> > OFFSET(fontsdir), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0,
> > FLAGS }, \
> > {"alpha", "enable processing of alpha channel",
> > OFFSET(alpha), AV_OPT_TYPE_BOOL, {.i64 = 0 },
> > 0, 1, FLAGS }, \
> > @@ -103,6 +106,16 @@ static av_cold int init(AVFilterContext *ctx)
> > return AVERROR(EINVAL);
> > }
> >
> > + if (ass->shift_opt) {
> > + if (av_parse_time(&ass->shift, ass->shift_opt, 1) < 0) {
> > + av_log(ctx, AV_LOG_ERROR, "Invalid subtitles shift: %s\n",
> > + ass->shift_opt);
> > + return AVERROR(EINVAL);
> > + }
> > + ass->shift = av_rescale_q(ass->shift, AV_TIME_BASE_Q,
> > av_make_q(1, 1000));
> > + av_log(ctx, AV_LOG_DEBUG, "Shifting subtitles by %0.3fsec.\n",
> > ass->shift/1000.0);
> > + }
> > +
> > ass->library = ass_library_init();
> > if (!ass->library) {
> > av_log(ctx, AV_LOG_ERROR, "Could not initialize libass.\n");
> > @@ -297,7 +310,7 @@ AVFILTER_DEFINE_CLASS(subtitles);
> >
> > static av_cold int init_subtitles(AVFilterContext *ctx)
> > {
> > - int j, ret, sid;
> > + int j, ret, sid, nskip;
> > int k = 0;
> > AVDictionary *codec_opts = NULL;
> > AVFormatContext *fmt = NULL;
> > @@ -448,6 +461,7 @@ static av_cold int init_subtitles(AVFilterContext *ctx)
> > av_init_packet(&pkt);
> > pkt.data = NULL;
> > pkt.size = 0;
> > + nskip = 0;
> > while (av_read_frame(fmt, &pkt) >= 0) {
> > int i, got_subtitle;
> > AVSubtitle sub = {0};
> > @@ -458,8 +472,17 @@ static av_cold int init_subtitles(AVFilterContext
> > *ctx)
> > av_log(ctx, AV_LOG_WARNING, "Error decoding: %s
> > (ignored)\n",
> > av_err2str(ret));
> > } else if (got_subtitle) {
> > - const int64_t start_time = av_rescale_q(sub.pts,
> > AV_TIME_BASE_Q, av_make_q(1, 1000));
> > + const int64_t start_time = av_rescale_q(sub.pts,
> > AV_TIME_BASE_Q, av_make_q(1, 1000)) + ass->shift;
> > const int64_t duration = sub.end_display_time;
> > +
> > + if (start_time + duration < 0) {
> > + nskip++;
> > + goto pkt_end;
> > + } else if (nskip > 0) {
> > + av_log(ctx, AV_LOG_INFO, "Skipped %d subtitles out of
> > time range.\n", nskip);
> > + nskip = 0;
> > + }
> > +
> > for (i = 0; i < sub.num_rects; i++) {
> > char *ass_line = sub.rects[i]->ass;
> > if (!ass_line)
> > @@ -472,6 +495,8 @@ static av_cold int init_subtitles(AVFilterContext *ctx)
> > }
> > }
> > }
> > +
> > +pkt_end:
> > av_packet_unref(&pkt);
> > avsubtitle_free(&sub);
> > }
> > --
> > 2.17.1
> >
> >
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--
Thanks,
Limin Wang
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