[FFmpeg-devel] [PATCH] avdevice/decklink: add option to drop frames till timecode is seen

[Marton Balint]

> From: Gyan Doshi <ffmpeg at gyani.pro>
> Date: Mon, 9 Sep 2019 18:33:09 +0530
> Subject: [PATCH v2] avdevice/decklink: add option to drop frames till timecode
>  is seen
> 
> Option wait_for_tc only takes effect if tc_format is set
> ---
>  doc/indevs.texi                 |  8 ++++++++
>  libavdevice/decklink_common.h   |  1 +
>  libavdevice/decklink_common_c.h |  1 +
>  libavdevice/decklink_dec.cpp    | 10 ++++++++++
>  libavdevice/decklink_dec_c.c    |  1 +
>  libavdevice/version.h           |  2 +-
>  6 files changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/indevs.texi b/doc/indevs.texi
> index 14595774f3..bc791013f2 100644
> --- a/doc/indevs.texi
> +++ b/doc/indevs.texi
> @@ -395,6 +395,14 @@ Either sync could go wrong by 1 frame or in a rarer case
>  @option{timestamp_align} seconds.
>  Defaults to @samp{0}.
> 
> + at item wait_for_tc (@emph{bool})
> +Drop frames till a frame with timecode is received. Sometimes serial timecode
> +isn't received with the first input frame. If that happens, the stored stream
> +timecode will be inaccurate. If this option is set to @option{true}, input frames
> +are dropped till a frame with timecode is received.
> +Option @var{timecode_format} must have been set.

I don't think "must have been" is correct here. Maybe simply write this:

Option @var{timecode_format} must also be specified.

> +Defaults to @option{false}.
> +
>  @end table
>
>  @subsection Examples
> diff --git a/libavdevice/decklink_common.h b/libavdevice/decklink_common.h
> index 921818ba41..35422a300b 100644
> --- a/libavdevice/decklink_common.h
> +++ b/libavdevice/decklink_common.h
> @@ -149,6 +149,7 @@ struct decklink_ctx {
>
>      int channels;
>      int audio_depth;
> +    unsigned long tc_seen;    // used with option wait_for_tc
>  };
>
>  typedef enum { DIRECTION_IN, DIRECTION_OUT} decklink_direction_t;
> diff --git a/libavdevice/decklink_common_c.h b/libavdevice/decklink_common_c.h
> index ca85ec2504..b78630b5fc 100644
> --- a/libavdevice/decklink_common_c.h
> +++ b/libavdevice/decklink_common_c.h
> @@ -58,6 +58,7 @@ struct decklink_cctx {
>      int copyts;
>      int64_t timestamp_align;
>      int timing_offset;
> +    int wait_for_tc;
>  };
>
>  #endif /* AVDEVICE_DECKLINK_COMMON_C_H */
> diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
> index 4da9122bff..ab7f28112e 100644
> --- a/libavdevice/decklink_dec.cpp
> +++ b/libavdevice/decklink_dec.cpp
> @@ -784,6 +784,8 @@ HRESULT decklink_input_callback::VideoInputFrameArrived(
>                              if (packed_metadata) {
>                                  if (av_packet_add_side_data(&pkt, AV_PKT_DATA_STRINGS_METADATA, packed_metadata, metadata_len) < 0)
>                                      av_freep(&packed_metadata);
> +                                else if (!ctx->tc_seen)
> +                                    ctx->tc_seen = ctx->frameCount;
>                              }
>                          }
>                      }
> @@ -793,6 +795,14 @@ HRESULT decklink_input_callback::VideoInputFrameArrived(
>              }
>          }
> 
> +        if (ctx->tc_format && cctx->wait_for_tc && !ctx->tc_seen) {
> +
> +            av_log(avctx, AV_LOG_WARNING, "No TC detected yet. wait_for_tc set. Dropping. \n");
> +            av_log(avctx, AV_LOG_WARNING, "Frame received (#%lu) - "
> +                        "- Frames dropped %u\n", ctx->frameCount, ++ctx->dropped);
> +            return S_OK;
> +        }
> +
>          pkt.pts = get_pkt_pts(videoFrame, audioFrame, wallclock, abs_wallclock, ctx->video_pts_source, ctx->video_st->time_base, &initial_video_pts, cctx->copyts);
>          pkt.dts = pkt.pts;
> 
> diff --git a/libavdevice/decklink_dec_c.c b/libavdevice/decklink_dec_c.c
> index 7aceaf934c..99439f91ae 100644
> --- a/libavdevice/decklink_dec_c.c
> +++ b/libavdevice/decklink_dec_c.c
> @@ -85,6 +85,7 @@ static const AVOption options[] = {
>      { "audio_depth",   "audio bitdepth (16 or 32)", OFFSET(audio_depth),  AV_OPT_TYPE_INT,   { .i64 = 16}, 16, 32, DEC },
>      { "decklink_copyts", "copy timestamps, do not remove the initial offset", OFFSET(copyts), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, DEC },
>      { "timestamp_align", "capture start time alignment (in seconds)", OFFSET(timestamp_align), AV_OPT_TYPE_DURATION, { .i64 = 0 }, 0, INT_MAX, DEC },
> +    { "wait_for_tc",     "drop frames till a frame with timecode is received. TC format must be set", OFFSET(wait_for_tc), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, DEC },
>      { NULL },
>  };
> 
> diff --git a/libavdevice/version.h b/libavdevice/version.h
> index e3a583d267..68302908cf 100644
> --- a/libavdevice/version.h
> +++ b/libavdevice/version.h
> @@ -29,7 +29,7 @@
>
>  #define LIBAVDEVICE_VERSION_MAJOR  58
>  #define LIBAVDEVICE_VERSION_MINOR   9
> -#define LIBAVDEVICE_VERSION_MICRO 100
> +#define LIBAVDEVICE_VERSION_MICRO 101
>
>  #define LIBAVDEVICE_VERSION_INT AV_VERSION_INT(LIBAVDEVICE_VERSION_MAJOR, \
>                                                 LIBAVDEVICE_VERSION_MINOR, \
> -- 
> 2.24.0

Otherwise LGTM.

Thanks,
Marton