[FFmpeg-user] Causes of color bars?

[Paul Blakeman]

You need to tell ffmpeg the Declink format you wish to use
1) List the formats available
2) Then use in command

e.g. 
1)
ffmpeg -f decklink -list_formats 1 -i "UltraStudio Mini Recorder"
[decklink @ 0x7fe28080b800] Supported formats for 'UltraStudio Mini Recorder':
format_code	description
ntsc	720x486 at 30000/1001 fps (interlaced, lower field first)
nt23	720x486 at 24000/1001 fps
pal 720x576 at 25000/1000 fps (interlaced, upper field first)
ntsp	720x486 at 60000/1001 fps
palp	720x576 at 50000/1000 fps
23ps	1920x1080 at 24000/1001 fps
24ps	1920x1080 at 24000/1000 fps
Hp25	1920x1080 at 25000/1000 fps
Hp29	1920x1080 at 30000/1001 fps
Hp30	1920x1080 at 30000/1000 fps
Hi50	1920x1080 at 25000/1000 fps (interlaced, upper field first)
Hi59	1920x1080 at 30000/1001 fps (interlaced, upper field first)
Hi60	1920x1080 at 30000/1000 fps (interlaced, upper field first)
hp50	1280x720 at 50000/1000 fps
hp59	1280x720 at 60000/1001 fps
hp60	1280x720 at 60000/1000 fps

(And then some examples of usage)
https://ffmpeg.org/ffmpeg-devices.html#Examples-1

e.g.
2)

ffmpeg -format_code Hi59 -f decklink -i "UltraStudio Mini Recorder" -preset superfast -crf 18 -minrate 8M -maxrate 8M -bufsize 10M -acodec libfdk_aac -vcodec libx264  -r 30 -f flv rtmp://xxxxx.com

Hope that helps

Regards,
Paul


On 14 Jul 2020, at 02:28, Simon Roberts <simon at dancingcloudservices.com> wrote:
> 
> Hi all,
> 
> I've been working with a Decklink Quad HDMI card under Ubuntu 20.04. The
> kernel driver is loaded and the Blackmagic software "mediaexpress" displays
> the input signal perfectly. However, when I try to use ffplay, it seems
> like it knows which of the four channels on the card has a signal, because
> it drops out with "can't determine format" on the other three, but when I
> ask to view the valid input signal, I simply get color bars.
> 
> I just built this version of ffmpeg with the decklink support, and it ran
> without any evident errors. I've done this before on another machine that
> didn't have a strong enough CPU for the concurrent capture I want to do,
> and everything worked properly.
> 
> So, my question is, what possible causes of color bars are there? I know
> that one is "if the input signal is lost", but it's claiming that it has a
> signal and it correctly identifies it as 1080 60p. I'm wondering if the
> bars are from the Decklink drivers, and not actually anything to do with
> ffmpeg/ffplay. How could I determine that?
> 
> This is the log output:
> 
> $ ffplay -f decklink -i 'DeckLink Quad HDMI Recorder (1)'
> ffplay version N-98470-g7772666 Copyright (c) 2003-2020 the FFmpeg
> developers
>  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
>  configuration: --prefix=/home/simon/ffmpeg_build
> --pkg-config-flags=--static
> --extra-cflags='-I/home/simon/ffmpeg_build/include
> -I/home/simon/ffmpeg_sources/BMD_SDK/include'
> --extra-ldflags=-L/home/simon/ffmpeg_build/lib --extra-libs='-lpthread -lm'
> --bindir=/home/simon/bin --enable-gpl --enable-libass --enable-libfdk-aac
> --enable-libfreetype --enable-libmp3lame --enable-libopus
> --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265
> --enable-nonfree --enable-decklink
>  libavutil      56. 55.100 / 56. 55.100
>  libavcodec     58. 95.100 / 58. 95.100
>  libavformat    58. 48.100 / 58. 48.100
>  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 @ 0x7fb628000bc0] Autodetected the input mode  0B f=0/0
> [decklink @ 0x7fb628000bc0] Found Decklink mode 1920 x 1080 with rate 59.94
> [decklink @ 0x7fb628000bc0] Frame received (#1) - No input signal detected
> - Frames dropped 1
> Input #0, decklink, from 'DeckLink Quad HDMI Recorder (1)': f=0/0
>  Duration: N/A, start: 0.000000, bitrate: 1990203 kb/s
>    Stream #0:0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
>    Stream #0:1: Video: rawvideo (UYVY / 0x59565955), uyvy422(progressive),
> 1920x1080, 1988667 kb/s, 59.94 tbr, 1000k tbn, 1000k tbc
>   1.23 A-V: -1.453 fd=  62 aq=  261KB vq=16200KB sq=    0B f=0/0
> 
> Thanks for any help!
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