[FFmpeg-devel] [PATCH] libavformat/concatdev.c: add unified_time_base opt

Ye Chuan yechuan0102 at hotmail.com
Tue Mar 1 13:45:59 EET 2022


In some case, the input files have different time base even though
they share the same codec and codec parameters,
While processing the packet, it will adjust the pts/dts by its own
time base instead of the unified one of the output stream, which may
lead to wrong pts/dts or unexpected speed change.

So this patch add the "unified_time_base" opt, which could be setted by
"-unified_time_base 1"
With the option, it will concatenate the input streams whose time base
are different , and won't course speed change issue.

Signed-off-by: Chuan Ye <yechuan0102 at hotmail.com>
---
libavformat/concatdec.c | 31 ++++++++++++++++++++++++-------
1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
index 0603c6e254..2cb656d87e 100644
--- a/libavformat/concatdec.c
+++ b/libavformat/concatdec.c
@@ -69,6 +69,7 @@ typedef struct {
    ConcatMatchMode stream_match_mode;
    unsigned auto_convert;
    int segment_time_metadata;
+    int unified_time_base;
} ConcatContext;

static int concat_probe(const AVProbeData *probe)
@@ -782,13 +783,27 @@ static int concat_read_packet(AVFormatContext *avf, AVPacket *pkt)
           av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
           av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));

-    delta = av_rescale_q(cat->cur_file->start_time - cat->cur_file->file_inpoint,
-                         AV_TIME_BASE_Q,
-                         cat->avf->streams[pkt->stream_index]->time_base);
-    if (pkt->pts != AV_NOPTS_VALUE)
-        pkt->pts += delta;
-    if (pkt->dts != AV_NOPTS_VALUE)
-        pkt->dts += delta;
+    if (cat->unified_time_base) {
+        /* replace the pkt base on the time base of target output stream */
+        AVRational output_tb;
+        output_tb = avf->streams[cs->out_stream_index]->time_base;
+        delta = av_rescale_q(cat->cur_file->start_time - cat->cur_file->file_inpoint,
+                             AV_TIME_BASE_Q,
+                             output_tb);
+        if (pkt->pts != AV_NOPTS_VALUE)
+            pkt->pts = av_rescale_q(pkt->pts, st->time_base, output_tb) + delta;
+        if (pkt->dts != AV_NOPTS_VALUE)
+            pkt->dts = av_rescale_q(pkt->dts, st->time_base, output_tb) + delta;
+    } else {
+        delta = av_rescale_q(cat->cur_file->start_time - cat->cur_file->file_inpoint,
+                             AV_TIME_BASE_Q,
+                             cat->avf->streams[pkt->stream_index]->time_base);
+        if (pkt->pts != AV_NOPTS_VALUE)
+            pkt->pts += delta;
+        if (pkt->dts != AV_NOPTS_VALUE)
+            pkt->dts += delta;
+    }
+
    av_log(avf, AV_LOG_DEBUG, " -> pts:%s pts_time:%s dts:%s dts_time:%s\n",
           av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
           av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));
@@ -931,6 +946,8 @@ static const AVOption options[] = {
      OFFSET(auto_convert), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, DEC },
    { "segment_time_metadata", "output file segment start time and duration as packet metadata",
      OFFSET(segment_time_metadata), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, DEC },
+    { "unified_time_base", "adjust to the same time base (from the first stream) while processing packets",
+      OFFSET(unified_time_base), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, DEC },
    { NULL }
};

-- 
2.30.1 (Apple Git-130)



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