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avcodec/bsf/setts: add option prescale

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When prescale is enabled, time fields are converted to the output
timebase before expression evaluation. This allows option specification
even if the input timebase is unknown.
This commit is contained in:
Gyan Doshi
2026-01-12 13:22:23 +05:30
parent 1ccd2f6243
commit 43dbc011fa
2 changed files with 29 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files
doc/bitstream_filters.texi
+3 -1
View File
@@ -913,6 +913,8 @@ Set expressions for PTS, DTS or both.
Set expression for duration.
@item time_base
Set output time base.
@item prescale
Set whether to convert time fields to user-set output time base before evaluation of expressions. Defaults to 0.
@end table
The expressions are evaluated through the eval API and can contain the following
@@ -973,7 +975,7 @@ The next input PTS.
The next input duration.
@item TB
The timebase of stream packet belongs.
The timebase in which time fields are denominated. The user-set output timebase if prescale is enabled, else the input timebase.
@item TB_OUT
The output timebase.
libavcodec/bsf/setts.c
+26 -17
View File
@@ -89,6 +89,7 @@ typedef struct SetTSContext {
AVRational time_base;
int user_outtb;
int prescale;
int64_t frame_number;
@@ -149,19 +150,26 @@ static int setts_init(AVBSFContext *ctx)
} else if (s->time_base.num || !s->time_base.den) {
av_log(ctx, AV_LOG_ERROR, "Invalid value %d/%d specified for output timebase\n", s->time_base.num, s->time_base.den);
return AVERROR_INVALIDDATA;
}
} else
s->prescale = 0;
s->frame_number= 0;
s->var_values[VAR_STARTPTS] = AV_NOPTS_VALUE;
s->var_values[VAR_STARTDTS] = AV_NOPTS_VALUE;
s->var_values[VAR_NOPTS] = AV_NOPTS_VALUE;
s->var_values[VAR_TB] = ctx->time_base_in.den ? av_q2d(ctx->time_base_in) : 0;
s->var_values[VAR_TB_OUT]= ctx->time_base_out.den ? av_q2d(ctx->time_base_out) : 0;
s->var_values[VAR_SR] = ctx->par_in->sample_rate;
if (s->user_outtb && s->prescale)
s->var_values[VAR_TB] = av_q2d(ctx->time_base_out);
else
s->var_values[VAR_TB] = ctx->time_base_in.den ? av_q2d(ctx->time_base_in) : 0;
return 0;
}
#define PRESCALED(x) ( s->prescale ? av_rescale_q(x, ctx->time_base_in, ctx->time_base_out) : x )
static int setts_filter(AVBSFContext *ctx, AVPacket *pkt)
{
SetTSContext *s = ctx->priv_data;
@@ -178,39 +186,39 @@ static int setts_filter(AVBSFContext *ctx, AVPacket *pkt)
}
if (s->var_values[VAR_STARTPTS] == AV_NOPTS_VALUE)
s->var_values[VAR_STARTPTS] = s->cur_pkt->pts;
s->var_values[VAR_STARTPTS] = PRESCALED(s->cur_pkt->pts);
if (s->var_values[VAR_STARTDTS] == AV_NOPTS_VALUE)
s->var_values[VAR_STARTDTS] = s->cur_pkt->dts;
s->var_values[VAR_STARTDTS] = PRESCALED(s->cur_pkt->dts);
s->var_values[VAR_N] = s->frame_number++;
s->var_values[VAR_TS] = s->cur_pkt->dts;
s->var_values[VAR_TS] = PRESCALED(s->cur_pkt->dts);
s->var_values[VAR_POS] = s->cur_pkt->pos;
s->var_values[VAR_PTS] = s->cur_pkt->pts;
s->var_values[VAR_DTS] = s->cur_pkt->dts;
s->var_values[VAR_DURATION] = s->cur_pkt->duration;
s->var_values[VAR_PREV_INPTS] = s->prev_inpkt->pts;
s->var_values[VAR_PREV_INDTS] = s->prev_inpkt->dts;
s->var_values[VAR_PREV_INDUR] = s->prev_inpkt->duration;
s->var_values[VAR_PTS] = PRESCALED(s->cur_pkt->pts);
s->var_values[VAR_DTS] = PRESCALED(s->cur_pkt->dts);
s->var_values[VAR_DURATION] = PRESCALED(s->cur_pkt->duration);
s->var_values[VAR_PREV_INPTS] = PRESCALED(s->prev_inpkt->pts);
s->var_values[VAR_PREV_INDTS] = PRESCALED(s->prev_inpkt->dts);
s->var_values[VAR_PREV_INDUR] = PRESCALED(s->prev_inpkt->duration);
s->var_values[VAR_PREV_OUTPTS] = s->prev_outpkt->pts;
s->var_values[VAR_PREV_OUTDTS] = s->prev_outpkt->dts;
s->var_values[VAR_PREV_OUTDUR] = s->prev_outpkt->duration;
s->var_values[VAR_NEXT_PTS] = pkt->pts;
s->var_values[VAR_NEXT_DTS] = pkt->dts;
s->var_values[VAR_NEXT_DUR] = pkt->duration;
s->var_values[VAR_NEXT_PTS] = PRESCALED(pkt->pts);
s->var_values[VAR_NEXT_DTS] = PRESCALED(pkt->dts);
s->var_values[VAR_NEXT_DUR] = PRESCALED(pkt->duration);
new_ts = llrint(av_expr_eval(s->ts_expr, s->var_values, NULL));
new_duration = llrint(av_expr_eval(s->duration_expr, s->var_values, NULL));
if (s->pts_str) {
s->var_values[VAR_TS] = s->cur_pkt->pts;
s->var_values[VAR_TS] = PRESCALED(s->cur_pkt->pts);
new_pts = llrint(av_expr_eval(s->pts_expr, s->var_values, NULL));
} else {
new_pts = new_ts;
}
if (s->dts_str) {
s->var_values[VAR_TS] = s->cur_pkt->dts;
s->var_values[VAR_TS] = PRESCALED(s->cur_pkt->dts);
new_dts = llrint(av_expr_eval(s->dts_expr, s->var_values, NULL));
} else {
new_dts = new_ts;
@@ -225,7 +233,7 @@ static int setts_filter(AVBSFContext *ctx, AVPacket *pkt)
if (ret < 0)
return ret;
if (s->user_outtb) {
if (s->user_outtb && !s->prescale) {
new_pts = av_rescale_q(new_pts, ctx->time_base_in, ctx->time_base_out);
new_dts = av_rescale_q(new_dts, ctx->time_base_in, ctx->time_base_out);
new_duration = av_rescale_q(new_duration, ctx->time_base_in, ctx->time_base_out);
@@ -269,6 +277,7 @@ static const AVOption options[] = {
{ "dts", "set expression for packet DTS", OFFSET(dts_str), AV_OPT_TYPE_STRING, {.str=NULL}, 0, 0, FLAGS },
{ "duration", "set expression for packet duration", OFFSET(duration_str), AV_OPT_TYPE_STRING, {.str="DURATION"}, 0, 0, FLAGS },
{ "time_base", "set output timebase", OFFSET(time_base), AV_OPT_TYPE_RATIONAL, {.dbl=0}, 0, INT_MAX, FLAGS },
{ "prescale", "convert to output timebase before evaluation", OFFSET(prescale), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
{ NULL },
};