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

Mon May 10 20:36:59 EEST 2021

On Mon, 10 May 2021, Anton Khirnov wrote:

> 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);

Maybe avpriv_dict_set_timestamp() should be used instead. That way 
milisecond precision can also be respected.

Thanks,
Marton

>         }
> 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_thumbnai
 l
> s=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
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>