[FFmpeg-devel] [PATCH] avformat: set start_time_realtime when demuxing

[Marton Balint]

On Tue, 14 Jun 2022, Gyan Doshi wrote:

> Add new flag AVFMT_START_REALTIME for the couple of demuxers that set it
> internally.

I don't think this is the same semantics.

start_time_realtime is the time when the stream was originally captured, 
and not when the stream was received. So you can't simply use av_gettime() 
in the demuxers for that field.

Regards.
Marton



> ---
> doc/APIchanges         | 3 +++
> libavformat/avformat.h | 1 +
> libavformat/demux.c    | 3 +++
> libavformat/rtsp.c     | 3 ++-
> libavformat/version.h  | 2 +-
> 5 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 5857e67ae6..4aa9e36777 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 AVFMT_START_REALTIME flag.
> +
> 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..4e247d68fc 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -499,6 +499,7 @@ typedef struct AVProbeData {
>                                         The user or muxer can override this through
>                                         AVFormatContext.avoid_negative_ts
>                                         */
> +#define AVFMT_START_REALTIME 0x80000 /**< Demuxer sets start_time_realtime */
>
> #define AVFMT_SEEK_TO_PTS   0x4000000 /**< Seeking is based on PTS */
>
> diff --git a/libavformat/demux.c b/libavformat/demux.c
> index 1620716716..28c6966e71 100644
> --- a/libavformat/demux.c
> +++ b/libavformat/demux.c
> @@ -628,6 +628,9 @@ FF_ENABLE_DEPRECATION_WARNINGS
>
>         force_codec_ids(s, st);
>
> +        if (!(s->iformat->flags & AVFMT_START_REALTIME) && s->start_time_realtime == AV_NOPTS_VALUE)
> +            s->start_time_realtime = 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/rtsp.c b/libavformat/rtsp.c
> index 88e9ef5226..2cafe33887 100644
> --- a/libavformat/rtsp.c
> +++ b/libavformat/rtsp.c
> @@ -2489,6 +2489,7 @@ const AVInputFormat ff_sdp_demuxer = {
>     .read_header    = sdp_read_header,
>     .read_packet    = ff_rtsp_fetch_packet,
>     .read_close     = sdp_read_close,
> +    .flags          = AVFMT_START_REALTIME,
>     .priv_class     = &sdp_demuxer_class,
> };
> #endif /* CONFIG_SDP_DEMUXER */
> @@ -2648,7 +2649,7 @@ const AVInputFormat ff_rtp_demuxer = {
>     .read_header    = rtp_read_header,
>     .read_packet    = ff_rtsp_fetch_packet,
>     .read_close     = sdp_read_close,
> -    .flags          = AVFMT_NOFILE,
> +    .flags          = AVFMT_NOFILE | AVFMT_START_REALTIME,
>     .priv_class     = &rtp_demuxer_class,
> };
> #endif /* CONFIG_RTP_DEMUXER */
> 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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