[FFmpeg-devel] [PATCH v1] lavf/img2enc: add support for option strftime_source

[Jun Li]

Currently the strftime option generate timestamp based on generation
time. The new option would calcualte timestamp from source's
start_realtime and pkt->pts, try to generate a timestamp matches the
source starting time.
---
 doc/muxers.texi       |  4 ++++
 libavformat/img2enc.c | 39 +++++++++++++++++++++++++++++++++++++++
 libavformat/rtsp.c    |  1 +
 3 files changed, 44 insertions(+)

diff --git a/doc/muxers.texi b/doc/muxers.texi
index 83ae017d6c..58d2d0ee7c 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -1190,6 +1190,10 @@ If set to 1, the filename will always be interpreted as just a
 filename, not a pattern, and the corresponding file will be continuously
 overwritten with new images. Default value is 0.
 
+ at item strftime_source
+If set to 1, expand the filename with date and time information from source.
+Useful when input is live stream like rtsp.
+
 @item strftime
 If set to 1, expand the filename with date and time information from
 @code{strftime()}. Default value is 0.
diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
index bec4bf81dd..8ba95ee3d5 100644
--- a/libavformat/img2enc.c
+++ b/libavformat/img2enc.c
@@ -45,6 +45,7 @@ typedef struct VideoMuxData {
     int frame_pts;
     const char *muxer;
     int use_rename;
+    int strftime_source;
 } VideoMuxData;
 
 static int write_header(AVFormatContext *s)
@@ -96,6 +97,7 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
             struct tm *tm, tmpbuf;
             time(&now0);
             tm = localtime_r(&now0, &tmpbuf);
+
             if (!strftime(filename, sizeof(filename), img->path, tm)) {
                 av_log(s, AV_LOG_ERROR, "Could not get frame filename with strftime\n");
                 return AVERROR(EINVAL);
@@ -105,6 +107,42 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
                 av_log(s, AV_LOG_ERROR, "Cannot write filename by pts of the frames.");
                 return AVERROR(EINVAL);
             }
+        } else if (img->strftime_source) {
+            int64_t start_realtime = s->start_time_realtime;
+            time_t sec = 0;
+            struct tm *tm;
+
+            if (start_realtime == AV_NOPTS_VALUE) {
+                // The value is not passed from input context to output, try to find in metadata.
+                AVDictionaryEntry *entry = av_dict_get(s->metadata, "start_realtime", NULL, 0);
+                if (entry) {
+                    av_log(s, AV_LOG_INFO, "Get start time from metadata start_realtime: %s\n", entry->value);
+                    start_realtime = strtoll(entry->value, NULL, 0);
+                } else {
+                    if (ff_parse_creation_time_metadata(s, &start_realtime, 0) != 0)
+                        av_log(s, AV_LOG_INFO, "Use creation_time as start_timestamp.\n");
+                }
+
+                if (start_realtime == 0 || start_realtime == AV_NOPTS_VALUE) {
+                    av_log(s, AV_LOG_WARNING, "Could not get start_realtime from source, set value to now.\n");
+                    time(&sec);
+                    s->start_time_realtime = sec * AV_TIME_BASE;
+                } else {
+                    s->start_time_realtime = start_realtime;
+                }
+            } 
+            
+            if (!sec) {
+                int64_t offset = av_rescale_q(pkt->pts, s->streams[0]->time_base, AV_TIME_BASE_Q);
+                int64_t timestamp = start_realtime + offset;
+                sec = timestamp / AV_TIME_BASE;
+            }
+
+            tm = gmtime(&sec);
+            if (!strftime(filename, sizeof(filename), img->path, tm)) {
+                av_log(s, AV_LOG_ERROR, "Could not get frame filename with strftime\n");
+                return AVERROR(EINVAL);
+            }
         } else if (av_get_frame_filename2(filename, sizeof(filename), img->path,
                                           img->img_number,
                                           AV_FRAME_FILENAME_FLAGS_MULTIPLE) < 0 &&
@@ -215,6 +253,7 @@ static const AVOption muxoptions[] = {
     { "strftime",     "use strftime for filename", OFFSET(use_strftime),  AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, ENC },
     { "frame_pts",    "use current frame pts for filename", OFFSET(frame_pts),  AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, ENC },
     { "atomic_writing", "write files atomically (using temporary files and renames)", OFFSET(use_rename), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, ENC },
+    { "strftime_source", "use strftime for filename and timestamp(UTC) from source if exists", OFFSET(strftime_source), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, ENC },
     { NULL },
 };
 
diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
index 8349840c96..16bb143ca6 100644
--- a/libavformat/rtsp.c
+++ b/libavformat/rtsp.c
@@ -2253,6 +2253,7 @@ redo:
                                         (uint64_t) rtpctx->st->time_base.num * 1000000,
                                                    rtpctx->st->time_base.den);
                     }
+                    av_dict_set_int(&s->metadata, "start_realtime", s->start_time_realtime, 0);
                 }
             }
             if (ret == -RTCP_BYE) {
-- 
2.17.1