[FFmpeg-user] Causes of color bars?
simon at dancingcloudservices.com
Tue Jul 14 16:17:02 EEST 2020
Thanks Paul and Marton for the input. I will note that the simple command,
entirely defaults-based, is what I used on a previous machine running with
the same card (same, not merely "same model"), and with the same input
device. That machine wasn't powerful enough to prores-encode four channels
simultaneously, so I built a bigger box. Also, the input source is not
adjustable, so it has not changed. The three things that have changed are
a) the new box has Ubuntu 20.04, while the old one has 18.04 (Decklink
claims support for 18.04, but doesn't mention 20.04), b) the CPU (was i7
and is now Ryzen 7) and c) the build of ffmpeg / the installation of the
decklink drivers (obviously in this context, I built both ffmpegs and
though there were no reported errors in the build, I wonder if I might have
done something wrong).
Regardless, I'll try setting the input format explicitly (I know for sure
that it's 1080, 60p, but I don't actually know for sure what the pixel
format is--it's reporting as 4:2:2 in the decklink "media player" that
reads the data successfully, so that seems a good start--but regardless,
there's likely to be some experimenting there.
I have also tried running with the verbose flag, but that didn't report
Is there a chance there is a permission issue, or a library location issue,
even though there are no errors reported?
Anyway, I'll go tinker with the format specifications and see if anything
changes. Fingers are crossed.
Thanks again for the suggestions!
On Tue, Jul 14, 2020 at 2:07 AM Paul Blakeman via ffmpeg-user <
ffmpeg-user at ffmpeg.org> wrote:
> You need to tell ffmpeg the Declink format you wish to use
> 1) List the formats available
> 2) Then use in command
> ffmpeg -f decklink -list_formats 1 -i "UltraStudio Mini Recorder"
> [decklink @ 0x7fe28080b800] Supported formats for 'UltraStudio Mini
> 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)
> 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
> On 14 Jul 2020, at 02:28, Simon Roberts <simon at dancingcloudservices.com>
> > 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"
> > 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,
> > 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
> > 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
> > --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
> > [decklink @ 0x7fb628000bc0] Frame received (#1) - No input signal
> > - 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),
> > 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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