no timecode via serial for decklink device

[dave rice]

Summary of the bug:

I'm able to get several of the timecode_formats options for the decklink device to work but have never gotten any input via the 'serial' timecode option, although other decklink tools can access this data.

How to reproduce:

I have an UltraStudio Express card with a remote RS422 cable set up for deckcontrol and timecode.

With the deckcontrol app at ​https://github.com/bavc/deckcontrol/blob/61616bb599a4458697d6e2d36d60a940a21ea3b6/deckcontrol.cpp#L267-L275, I can access the timecode over serial like this:

% deckcontrol gettimecode

Issued command 'gettimecode'
TC=02:05:39:11
Command sucessfully issued
Error sending command (No error)

But with ffmpeg, I only get an N/A value for timecode.

% ffprobe -f decklink -timecode_format serial -format_code ntsc -video_input composite -audio_input analog -i 'UltraStudio Express' -show_streams

ffprobe version git-2020-07-28-a45935f Copyright (c) 2007-2020 the FFmpeg developers
  built with Apple LLVM version 10.0.1 (clang-1001.0.46.4)
  configuration: --prefix=/usr/local/Cellar/ffmpegdecklink/HEAD-a45935f --disable-shared --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-libfreetype --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libsnappy --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-libfontconfig --disable-libjack --disable-indev=jack --enable-nonfree --enable-decklink --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/include
  libavutil      56. 57.100 / 56. 57.100
  libavcodec     58. 97.102 / 58. 97.102
  libavformat    58. 49.100 / 58. 49.100
  libavdevice    58. 11.101 / 58. 11.101
  libavfilter     7. 87.100 /  7. 87.100
  libswscale      5.  8.100 /  5.  8.100
  libswresample   3.  8.100 /  3.  8.100
  libpostproc    55.  8.100 / 55.  8.100
[decklink @ 0x7fd330802a00] Found Decklink mode 720 x 486 with rate 29.97(i)
[decklink @ 0x7fd330802a00] Frame received (#3) - No input signal detected - Frames dropped 1
[decklink @ 0x7fd330802a00] Frame received (#5) - Input returned - Frames dropped 2
Input #0, decklink, from 'UltraStudio Express':
  Duration: N/A, start: 0.000000, bitrate: 169329 kb/s
    Stream #0:0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
    Stream #0:1: Video: rawvideo (UYVY / 0x59565955), uyvy422(bottom first), 720x486, 167793 kb/s, 29.97 fps, 29.97 tbr, 1000k tbn, 1000k tbc
[STREAM]
index=0
codec_name=pcm_s16le
codec_long_name=PCM signed 16-bit little-endian
profile=unknown
codec_type=audio
codec_time_base=1/48000
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
sample_fmt=s16
sample_rate=48000
channels=2
channel_layout=unknown
bits_per_sample=16
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/1000000
start_pts=0
start_time=0.000000
duration_ts=N/A
duration=N/A
bit_rate=1536000
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
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
[/STREAM]
[STREAM]
index=1
codec_name=rawvideo
codec_long_name=raw video
profile=unknown
codec_type=video
codec_time_base=1001/30000
codec_tag_string=UYVY
codec_tag=0x59565955
width=720
height=486
coded_width=720
coded_height=486
closed_captions=0
has_b_frames=0
sample_aspect_ratio=N/A
display_aspect_ratio=N/A
pix_fmt=uyvy422
level=-99
color_range=unknown
color_space=unknown
color_transfer=unknown
color_primaries=unknown
chroma_location=unspecified
field_order=bb
timecode=N/A
refs=1
id=N/A
r_frame_rate=30000/1001
avg_frame_rate=30000/1001
time_base=1/1000000
start_pts=0
start_time=0.000000
duration_ts=N/A
duration=N/A
bit_rate=167793806
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
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
[/STREAM]

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.