Would it be possible to have a quick review for this patch? It is pretty
straightforward.
Plus, this is its second submission. It already includes the requested
changes from the first time (~1y ago).
Thanks in advance,
Manolis
On Sun, 4 Jul 2021 at 18:13, 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 | 11 ++++++++
> libavfilter/vf_subtitles.c | 55 +++++++++++++++++++++++++++++++++-----
> 2 files changed, 59 insertions(+), 7 deletions(-)
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 61c4cfc150..eebf455692 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -19474,6 +19474,9 @@ Common @ref{subtitles}/@ref{ass} filter 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
> @@ -19487,6 +19490,9 @@ These fonts will be used in addition to whatever
> the font provider uses.
>
> @item alpha
> Process alpha channel, by default alpha channel is untouched.
> +
> +@item shift
> +Shift subtitles timings by the specified amount.
> @end table
>
> Additional options for @ref{subtitles} filter:
> @@ -19533,6 +19539,11 @@ 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 ab32e1b7f3..2c7ce267e1 100644
> --- a/libavfilter/vf_subtitles.c
> +++ b/libavfilter/vf_subtitles.c
> @@ -52,6 +52,7 @@ typedef struct AssContext {
> char *filename;
> char *fontsdir;
> char *charenc;
> + int64_t shift;
> char *force_style;
> int stream_index;
> int alpha;
> @@ -66,11 +67,12 @@ typedef struct AssContext {
> #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
>
> #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 }, \
> - {"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 }, \
> + {"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 }, \
> + {"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 }, \
> + {"shift", "shift subtitles timing",
> OFFSET(shift), AV_OPT_TYPE_DURATION, {.i64 = 0 },
> INT64_MIN, INT64_MAX, FLAGS }, \
>
> /* libass supports a log level ranging from 0 to 7 */
> static const int ass_libavfilter_log_level_map[] = {
> @@ -103,6 +105,11 @@ static av_cold int init(AVFilterContext *ctx)
> return AVERROR(EINVAL);
> }
>
> + if (ass->shift != 0) {
> + ass->shift = av_rescale_q(ass->shift, AV_TIME_BASE_Q,
> av_make_q(1, 1000));
> + av_log(ctx, AV_LOG_INFO, "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");
> @@ -228,6 +235,8 @@ AVFILTER_DEFINE_CLASS(ass);
>
> static av_cold int init_ass(AVFilterContext *ctx)
> {
> + int eid, nskip;
> + ASS_Event *event;
> AssContext *ass = ctx->priv;
> int ret = init(ctx);
>
> @@ -244,6 +253,25 @@ static av_cold int init_ass(AVFilterContext *ctx)
> ass->filename);
> return AVERROR(EINVAL);
> }
> +
> + /* Shift subtitles. */
> + nskip = 0;
> + for (eid = 0; eid < ass->track->n_events; eid++) {
> + event = &ass->track->events[eid];
> + event->Start += ass->shift;
> + if (event->Start + event->Duration < 0) {
> + ass_free_event(ass->track, eid);
> + nskip++;
> + continue;
> + } else if (nskip > 0) {
> + av_log(ctx, AV_LOG_INFO, "Skipped %d subtitles out of time
> range.\n", nskip);
> + memmove(event - nskip, event, (ass->track->n_events - eid) *
> sizeof(ASS_Event));
> + ass->track->n_events -= nskip;
> + eid -= nskip;
> + nskip = 0;
> + }
> + }
> +
> return 0;
> }
>
> @@ -298,7 +326,7 @@ 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;
> @@ -449,6 +477,7 @@ static av_cold int init_subtitles(AVFilterContext *ctx)
> ass_process_codec_private(ass->track,
> dec_ctx->subtitle_header,
> dec_ctx->subtitle_header_size);
> + nskip = 0;
> while (av_read_frame(fmt, &pkt) >= 0) {
> int i, got_subtitle;
> AVSubtitle sub = {0};
> @@ -459,8 +488,18 @@ 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));
> + /* Shift subtitles. */
> + 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)
> @@ -470,6 +509,8 @@ static av_cold int init_subtitles(AVFilterContext *ctx)
> }
> }
> }
> +
> +pkt_end:
> av_packet_unref(&pkt);
> avsubtitle_free(&sub);
> }
> --
> 2.17.1
>
>
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