[FFmpeg-devel] [PATCH v2 1/2] avformat: add AVFormatContext.first_pkt_wallclock

[Gyan Doshi <ffmpeg@gyani.pro>]

Stores wallclock time for the first packet received.
Used for crude sync offset among inputs.
---
 doc/APIchanges         |  3 +++
 libavformat/avformat.h | 10 ++++++++++
 libavformat/demux.c    |  3 +++
 libavformat/options.c  |  1 +
 libavformat/version.h  |  2 +-
 5 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index 20b944933a..94c53d283f 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -14,6 +14,9 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2022-06-xx - xxxxxxxxxx - lavf 59.26.100 - avformat.h
+  Add and set AVFormatContext.first_pkt_wallclock field.
+
 2022-06-12 - xxxxxxxxxx - lavf 59.25.100 - avio.h
   Add avio_vprintf(), similar to avio_printf() but allow to use it
   from within a function taking a variable argument list as input.
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index f12fa7d904..a45777ab39 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1808,6 +1808,16 @@ typedef struct AVFormatContext {
      */
     int max_probe_packets;
 
+    /**
+     * Wallclock start time of the stream in real world time, in microseconds
+     * since the Unix epoch (00:00 1st January 1970). That is, the first packet
+     * was received at this real world time.
+     * - demuxing: Set by libavformat. Users may want to use start_time_realtime
+     *             if set.
+     * - muxing: unused.
+     */
+    int64_t first_pkt_wallclock;
+
     /**
      * A callback for closing the streams opened with AVFormatContext.io_open().
      *
diff --git a/libavformat/demux.c b/libavformat/demux.c
index e121253dfd..7e0540debf 100644
--- a/libavformat/demux.c
+++ b/libavformat/demux.c
@@ -628,6 +628,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
         force_codec_ids(s, st);
 
+        if (s->first_pkt_wallclock == AV_NOPTS_VALUE)
+            s->first_pkt_wallclock = av_gettime();
+
         /* TODO: audio: time filter; video: frame reordering (pts != dts) */
         if (s->use_wallclock_as_timestamps)
             pkt->dts = pkt->pts = av_rescale_q(av_gettime(), AV_TIME_BASE_Q, st->time_base);
diff --git a/libavformat/options.c b/libavformat/options.c
index 0079a06d9a..77d4dfd1d0 100644
--- a/libavformat/options.c
+++ b/libavformat/options.c
@@ -184,6 +184,7 @@ AVFormatContext *avformat_alloc_context(void)
         return NULL;
     }
 
+    s->first_pkt_wallclock = AV_NOPTS_VALUE;
     si->shortest_end = AV_NOPTS_VALUE;
 
     return s;
diff --git a/libavformat/version.h b/libavformat/version.h
index 966ebb7ed3..0708d619c0 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFORMAT_VERSION_MINOR  25
+#define LIBAVFORMAT_VERSION_MINOR  26
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
-- 
2.36.1

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