[FFmpeg-devel] [PATCH] libavformat/concatdev.c: Add unified_time_base option

* [FFmpeg-devel] [PATCH] libavformat/concatdev.c: Add unified_time_base option
@ 2022-03-01 12:40 Ye Chuan
  0 siblings, 0 replies; 2+ messages in thread
From: Ye Chuan @ 2022-03-01 12:40 UTC (permalink / raw)
  To: ffmpeg-devel

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@hotmail.com<mailto:yechuan0102@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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