Hello,
I'm able to capture from a windows desktop and send that out a Blackmagic
DeckLink card (in NTSC format), however there is a substantial delay, almost
a second, between the windowz direct-connected monitor and the SDI monitor.
Thoughts on why this is happening? The system is not CPU bound, indeed, it's
largely idle. Even scaling from 800x600 to 720x486 and converting the
pix_fmt shouldn't take long and I wouldn't expect any encode/decode or other
processing along the way.
The content I'm testing with is entirely still images played though a
slide-show program; the fades between slides look fairly smooth on the SDI,
just later than expected. (The screen is set to 800x600 as a convenience,
it's the lowest 4:3 resolution the video card will do.)
# ./ffmpeg.exe -f gdigrab -draw_mouse 0 -framerate 30000/1001 -offset_x 1920
-offset_y 0 -video_size 800x600 -i desktop -f decklink -pix_fmt uyvy422 -s
720x486 -r 30000/1001 "DeckLink SDI 4K"
ffmpeg version N-91991-gc02ff77681-static Copyright (c) 2000-2018 the FFmpeg
developers
built with gcc 8.2.0 (Rev1, Built by MSYS2 project)
configuration: --extra-cflags=-I/mingw64/include
--extra-ldflags=-L/mingw64/lib --extra-version=static
--extra-cflags=--static --enable-static --disable-debug --disable-shared
--disable-ffplay --disable-ffprobe --disable-doc --enable-decklink
--enable-avfilter --extra-cflags=-I/mingw64/include/BMD
libavutil 56. 19.101 / 56. 19.101
libavcodec 58. 30.100 / 58. 30.100
libavformat 58. 18.101 / 58. 18.101
libavdevice 58. 4.103 / 58. 4.103
libavfilter 7. 32.100 / 7. 32.100
libswscale 5. 2.100 / 5. 2.100
libswresample 3. 2.100 / 3. 2.100
[gdigrab @ 00000000006ebbc0] Capturing whole desktop as 800x600x32 at (1920,0)
Input #0, gdigrab, from 'desktop':
Duration: N/A, start: 1537916427.265766, bitrate: 460352 kb/s
Stream #0:0: Video: bmp, bgra, 800x600, 460352 kb/s, 29.97 fps, 33 tbr,
1000k tbn, 1000k tbc
Stream mapping:
Stream #0:0 -> #0:0 (bmp (native) -> wrapped_avframe (native))
Press [q] to stop, [?] for help
[decklink @ 000000000079d040] Found Decklink mode 720 x 486 with rate 29.97(i)
Output #0, decklink, to 'DeckLink SDI 4K':
Metadata:
encoder : Lavf58.18.101
Stream #0:0: Video: wrapped_avframe, uyvy422, 720x486, q=2-31, 200
kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
Metadata:
encoder : Lavc58.30.100 wrapped_avframe
frame=2411422 fps= 30 q=-0.0 size=N/A time=22:21:01.11 bitrate=N/A dup=19
drop=4 speed= 1x
(still running after 22 hours :) )
As a side note, I hate dealing with the non-square pixels of NTSC.
Later,
z!
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