[FFmpeg-devel] [PATCH v1 2/2] avfilter/vf_subtitles: Added shift option for subtitles/ass filters.
Gyan Doshi
ffmpeg at gyani.pro
Thu Jul 22 16:19:20 EEST 2021
On 2021-07-22 00:08, Manolis Stamatogiannakis wrote:
> Would it be possible to have a quick review for this patch? It is pretty
> straightforward.
Will test within a few days.
Regards,
Gyan
>
> 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 <mstamat at 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 <mstamat at 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.
>>
>> + at 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.
>> +
>> + at 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:
>> + at example
>> +subtitles=filename=sub.srt:shift='-20\:20'
>> + at 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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