[FFmpeg-devel] [PATCH] lavf/flvdec: normalize exporting date metadata

[Anton Khirnov]

Export them in UTC, not the local timezone. This way the output is
the same everywhere. The timezone information stored in the file is
still ignored, since there seems to be no simple way to export it
correctly.

Format them according to ISO 8601, which we generally use for exporting
dates.
---
If anyone has practical suggestions for exporting the timezone, I would
love to hear them. Don't see anything in the standard library for
"express this UTC timestamp in a given timezone". Just adding the offset
to the timestamp would AFAIU not be correct wrt leap seconds (and maybe
something else? dates are hard).

Also, the conversion of double to time_t is potentially UB if the source
value is out of range, but there seems to be no standard way to check,
since the range of time_t is not standard either. Anyone got any ideas?
---
 libavformat/flvdec.c     | 7 +++++--
 tests/ref/fate/flv-demux | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index e6c2877a74..ddaceaafe4 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -686,8 +686,11 @@ static int amf_parse_object(AVFormatContext *s, AVStream *astream,
             struct tm t;
             char datestr[128];
             time =  date.milliseconds / 1000; // to seconds
-            localtime_r(&time, &t);
-            strftime(datestr, sizeof(datestr), "%a, %d %b %Y %H:%M:%S %z", &t);
+            gmtime_r(&time, &t);
+
+            // timezone is ignored, since there is no easy way to offset the UTC
+            // timestamp into the specified timezone
+            strftime(datestr, sizeof(datestr), "%Y-%m-%dT%H:%M:%SZ", &t);
 
             av_dict_set(&s->metadata, key, datestr, 0);
         }
diff --git a/tests/ref/fate/flv-demux b/tests/ref/fate/flv-demux
index 30435adeb9..827b56ea09 100644
--- a/tests/ref/fate/flv-demux
+++ b/tests/ref/fate/flv-demux
@@ -605,4 +605,4 @@ packet|codec_type=audio|stream_index=1|pts=11656|pts_time=11.656000|dts=11656|dt
 packet|codec_type=video|stream_index=0|pts=11678|pts_time=11.678000|dts=11678|dts_time=11.678000|duration=33|duration_time=0.033000|size=1190|pos=510794|flags=__|data_hash=CRC32:a0206c90
 stream|index=0|codec_name=h264|profile=77|codec_type=video|codec_tag_string=[0][0][0][0]|codec_tag=0x0000|width=426|height=240|coded_width=426|coded_height=240|closed_captions=0|has_b_frames=1|sample_aspect_ratio=1:1|display_aspect_ratio=71:40|pix_fmt=yuv420p|level=21|color_range=unknown|color_space=unknown|color_transfer=unknown|color_primaries=unknown|chroma_location=left|field_order=progressive|refs=1|is_avc=true|nal_length_size=4|id=N/A|r_frame_rate=30000/1001|avg_frame_rate=30/1|time_base=1/1000|start_pts=0|start_time=0.000000|duration_ts=N/A|duration=N/A|bit_rate=393929|max_bit_rate=N/A|bits_per_raw_sample=8|nb_frames=N/A|nb_read_frames=N/A|nb_read_packets=351|extradata_hash=CRC32:07b85ca9|disposition:default=0|disposition:dub=0|disposition:original=0|disposition:comment=0|disposition:lyrics=0|disposition:karaoke=0|disposition:forced=0|disposition:hearing_impaired=0|disposition:visual_impaired=0|disposition:clean_effects=0|disposition:attached_pic=0|disposition:timed_thumbnails=0|disposition:captions=0|disposition:descriptions=0|disposition:metadata=0|disposition:dependent=0|disposition:still_image=0
 stream|index=1|codec_name=aac|profile=1|codec_type=audio|codec_tag_string=[0][0][0][0]|codec_tag=0x0000|sample_fmt=fltp|sample_rate=22050|channels=2|channel_layout=stereo|bits_per_sample=0|id=N/A|r_frame_rate=0/0|avg_frame_rate=0/0|time_base=1/1000|start_pts=0|start_time=0.000000|duration_ts=N/A|duration=N/A|bit_rate=67874|max_bit_rate=N/A|bits_per_raw_sample=N/A|nb_frames=N/A|nb_read_frames=N/A|nb_read_packets=252|extradata_hash=CRC32:d039c029|disposition:default=0|disposition:dub=0|disposition:original=0|disposition:comment=0|disposition:lyrics=0|disposition:karaoke=0|disposition:forced=0|disposition:hearing_impaired=0|disposition:visual_impaired=0|disposition:clean_effects=0|disposition:attached_pic=0|disposition:timed_thumbnails=0|disposition:captions=0|disposition:descriptions=0|disposition:metadata=0|disposition:dependent=0|disposition:still_image=0
-format|filename=Enigma_Principles_of_Lust-part.flv|nb_streams=2|nb_programs=0|format_name=flv|start_time=0.000000|duration=210.209999|size=512000|bit_rate=19485|probe_score=100|tag:hasKeyframes=true|tag:hasMetadata=true|tag:datasize=11970544|tag:hasVideo=true|tag:canSeekToEnd=false|tag:lasttimestamp=210|tag:lastkeyframetimestamp=210|tag:audiosize=1791332|tag:hasAudio=true|tag:audiodelay=0|tag:videosize=10176110|tag:metadatadate=Sun, 27 Feb 2011 12:00:33 +0100|tag:metadatacreator=inlet media FLVTool2 v1.0.6 - http://www.inlet-media.de/flvtool2|tag:hasCuePoints=false
+format|filename=Enigma_Principles_of_Lust-part.flv|nb_streams=2|nb_programs=0|format_name=flv|start_time=0.000000|duration=210.209999|size=512000|bit_rate=19485|probe_score=100|tag:hasKeyframes=true|tag:hasMetadata=true|tag:datasize=11970544|tag:hasVideo=true|tag:canSeekToEnd=false|tag:lasttimestamp=210|tag:lastkeyframetimestamp=210|tag:audiosize=1791332|tag:hasAudio=true|tag:audiodelay=0|tag:videosize=10176110|tag:metadatadate=2011-02-27T11:00:33Z|tag:metadatacreator=inlet media FLVTool2 v1.0.6 - http://www.inlet-media.de/flvtool2|tag:hasCuePoints=false
-- 
2.30.2