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 }, \
> {"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
>
>
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
