[FFmpeg-devel] [PATCH v4] ffmpeg: add option -isync
Gyan Doshi
ffmpeg at gyani.pro
Thu Jul 14 13:21:39 EEST 2022
Pushed as 882aac99d2a7d15492ce1da9859676b0c04295b8
and cherry-picked to 5.1
On 2022-07-14 01:46 pm, Gyan Doshi wrote:
> This is a per-file input option that adjusts an input's timestamps
> with reference to another input, so that emitted packet timestamps
> account for the difference between the start times of the two inputs.
>
> Typical use case is to sync two or more live inputs such as from capture
> devices. Both the target and reference input source timestamps should be
> based on the same clock source.
>
> If either input lacks starting timestamps, then no sync adjustment is made.
> ---
> v4 change: fallback on reception timestamp removed.
>
> doc/ffmpeg.texi | 15 +++++++++++
> fftools/ffmpeg.h | 2 ++
> fftools/ffmpeg_opt.c | 60 ++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 77 insertions(+)
>
> diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
> index 1a534ff1cc..767df69b7f 100644
> --- a/doc/ffmpeg.texi
> +++ b/doc/ffmpeg.texi
> @@ -518,6 +518,21 @@ see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1)
> Like the @code{-ss} option but relative to the "end of file". That is negative
> values are earlier in the file, 0 is at EOF.
>
> + at item -isync @var{input_index} (@emph{input})
> +Assign an input as a sync source.
> +
> +This will take the difference between the start times of the target and reference inputs and
> +offset the timestamps of the target file by that difference. The source timestamps of the two
> +inputs should derive from the same clock source for expected results. If @code{copyts} is set
> +then @code{start_at_zero} must also be set. If either of the inputs has no starting timestamp
> +then no sync adjustment is made.
> +
> +Acceptable values are those that refer to a valid ffmpeg input index. If the sync reference is
> +the target index itself or @var{-1}, then no adjustment is made to target timestamps. A sync
> +reference may not itself be synced to any other input.
> +
> +Default value is @var{-1}.
> +
> @item -itsoffset @var{offset} (@emph{input})
> Set the input time offset.
>
> diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
> index 99d31c346e..391a35cf50 100644
> --- a/fftools/ffmpeg.h
> +++ b/fftools/ffmpeg.h
> @@ -118,6 +118,7 @@ typedef struct OptionsContext {
> float readrate;
> int accurate_seek;
> int thread_queue_size;
> + int input_sync_ref;
>
> SpecifierOpt *ts_scale;
> int nb_ts_scale;
> @@ -410,6 +411,7 @@ typedef struct InputFile {
> at the moment when looping happens */
> AVRational time_base; /* time base of the duration */
> int64_t input_ts_offset;
> + int input_sync_ref;
>
> int64_t ts_offset;
> int64_t last_ts;
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index e08455478f..359d8f60b8 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -235,6 +235,7 @@ static void init_options(OptionsContext *o)
> o->chapters_input_file = INT_MAX;
> o->accurate_seek = 1;
> o->thread_queue_size = -1;
> + o->input_sync_ref = -1;
> }
>
> static int show_hwaccels(void *optctx, const char *opt, const char *arg)
> @@ -287,6 +288,59 @@ static int parse_and_set_vsync(const char *arg, int *vsync_var, int file_idx, in
> return 0;
> }
>
> +static int apply_sync_offsets(void)
> +{
> + for (int i = 0; i < nb_input_files; i++) {
> + InputFile *ref, *self = input_files[i];
> + int64_t adjustment;
> + int64_t self_start_time, ref_start_time, self_seek_start, ref_seek_start;
> + int start_times_set = 1;
> +
> + if (self->input_sync_ref == -1 || self->input_sync_ref == i) continue;
> + if (self->input_sync_ref >= nb_input_files || self->input_sync_ref < -1) {
> + av_log(NULL, AV_LOG_FATAL, "-isync for input %d references non-existent input %d.\n", i, self->input_sync_ref);
> + exit_program(1);
> + }
> +
> + if (copy_ts && !start_at_zero) {
> + av_log(NULL, AV_LOG_FATAL, "Use of -isync requires that start_at_zero be set if copyts is set.\n");
> + exit_program(1);
> + }
> +
> + ref = input_files[self->input_sync_ref];
> + if (ref->input_sync_ref != -1 && ref->input_sync_ref != self->input_sync_ref) {
> + av_log(NULL, AV_LOG_ERROR, "-isync for input %d references a resynced input %d. Sync not set.\n", i, self->input_sync_ref);
> + continue;
> + }
> +
> + if (self->ctx->start_time_realtime != AV_NOPTS_VALUE && ref->ctx->start_time_realtime != AV_NOPTS_VALUE) {
> + self_start_time = self->ctx->start_time_realtime;
> + ref_start_time = ref->ctx->start_time_realtime;
> + } else if (self->ctx->start_time != AV_NOPTS_VALUE && ref->ctx->start_time != AV_NOPTS_VALUE) {
> + self_start_time = self->ctx->start_time;
> + ref_start_time = ref->ctx->start_time;
> + } else {
> + start_times_set = 0;
> + }
> +
> + if (start_times_set) {
> + self_seek_start = self->start_time == AV_NOPTS_VALUE ? 0 : self->start_time;
> + ref_seek_start = ref->start_time == AV_NOPTS_VALUE ? 0 : ref->start_time;
> +
> + adjustment = (self_start_time - ref_start_time) + !copy_ts*(self_seek_start - ref_seek_start) + ref->input_ts_offset;
> +
> + self->ts_offset += adjustment;
> +
> + av_log(NULL, AV_LOG_INFO, "Adjusted ts offset for Input #%d by %"PRId64" us to sync with Input #%d.\n", i, adjustment, self->input_sync_ref);
> + } else {
> + av_log(NULL, AV_LOG_INFO, "Unable to identify start times for Inputs #%d and %d both. No sync adjustment made.\n",
> + i, self->input_sync_ref);
> + }
> + }
> +
> + return 0;
> +}
> +
> static int opt_filter_threads(void *optctx, const char *opt, const char *arg)
> {
> av_free(filter_nbthreads);
> @@ -1305,6 +1359,7 @@ static int open_input_file(OptionsContext *o, const char *filename)
> f->ist_index = nb_input_streams - ic->nb_streams;
> f->start_time = o->start_time;
> f->recording_time = o->recording_time;
> + f->input_sync_ref = o->input_sync_ref;
> f->input_ts_offset = o->input_ts_offset;
> f->ts_offset = o->input_ts_offset - (copy_ts ? (start_at_zero && ic->start_time != AV_NOPTS_VALUE ? ic->start_time : 0) : timestamp);
> f->nb_streams = ic->nb_streams;
> @@ -3489,6 +3544,8 @@ int ffmpeg_parse_options(int argc, char **argv)
> goto fail;
> }
>
> + apply_sync_offsets();
> +
> /* create the complex filtergraphs */
> ret = init_complex_filters();
> if (ret < 0) {
> @@ -3603,6 +3660,9 @@ const OptionDef options[] = {
> { "accurate_seek", OPT_BOOL | OPT_OFFSET | OPT_EXPERT |
> OPT_INPUT, { .off = OFFSET(accurate_seek) },
> "enable/disable accurate seeking with -ss" },
> + { "isync", HAS_ARG | OPT_INT | OPT_OFFSET |
> + OPT_EXPERT | OPT_INPUT, { .off = OFFSET(input_sync_ref) },
> + "Indicate the input index for sync reference", "sync ref" },
> { "itsoffset", HAS_ARG | OPT_TIME | OPT_OFFSET |
> OPT_EXPERT | OPT_INPUT, { .off = OFFSET(input_ts_offset) },
> "set the input ts offset", "time_off" },
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