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Detect 1 sec black at the end of files
Posted: Thu Jul 21, 2022 11:32 am
by Ian_Grey
Hi,
I am using FFAStrans to check master files against various broadcaster tech specs and it is working remarkable well.
One broadcaster needs to have 1 sec of black at the end of a file that operators sometimes miss. Is there a way to detect if a file has black for the last 25frames of the file?
Re: Detect 1 sec black at the end of files
Posted: Thu Jul 21, 2022 12:16 pm
by emcodem
Hey Mr Grey,
lucky you just yesterday i did the same but 1 frame at start. I did alter it for you:
Please try out this one. Check out the commandline processor parameters,
Tells ffmpeg to seek -1 second from end.
Tells ffmpeg to alert if 0.9 seconds were black.
Just edit the values until it detects exactly what you like.
Take care, you cannot seek to -1 seconds and seek for 1 second black because the blackdetect would only report if black is longer than 1 second, so it would never detect because you only check exactly 1 second.
Also, if you seek -2 seconds and detect 1 second black, you would be notified that there is 1 second black WITHIN the last 2 seconds, not at the very end where you are looking for it to be.
Also, if there is too much black detected, you might want to add a thresshold, e.g.
blackdetect=d=2:pix_th=0.00
https://ffmpeg.org/ffmpeg-filters.html#blackdetect
Re: Detect 1 sec black at the end of files
Posted: Thu Jul 21, 2022 3:19 pm
by emcodem
and @Ian_Grey please don't forget to report if it worked or if you maybe did it totally different in the end. It is always helpful for forum readers to know if the proposed stuff worked or not
Re: Detect 1 sec black at the end of files
Posted: Thu Feb 09, 2023 6:39 pm
by movalex
I think the -sseof -1 option does not work for the blacks detect.
Code: Select all
ffmpeg -i "D:\RENDER\test_black.avi" -sseof -1 -vf "blackframe=thresh=32:amount=50" -an -f null - 2>&1 | findstr "Parsed_blackframe" >> "blacks.txt"
At least for me it does not return anything despite there's some blacks frames present at the end.
However if I manually run blackframe check over the whole file, I receive a list of black frames relatively quickly:
Code: Select all
ffmpeg -i "D:\RENDER\test_black.avi" -vf "blackframe=thresh=32:amount=50" -an -f null - 2>&1 | findstr "Parsed_blackframe" >> "blacks.txt"
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:0 pblack:100 pts:0 t:0.000000 type:I last_keyframe:0
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:1 pblack:100 pts:1 t:0.040000 type:I last_keyframe:1
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:2 pblack:99 pts:2 t:0.080000 type:I last_keyframe:2
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:3 pblack:57 pts:3 t:0.120000 type:I last_keyframe:3
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:42 pblack:93 pts:42 t:1.680000 type:I last_keyframe:42
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:43 pblack:100 pts:43 t:1.720000 type:I last_keyframe:43
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:44 pblack:100 pts:44 t:1.760000 type:I last_keyframe:44
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:45 pblack:100 pts:45 t:1.800000 type:I last_keyframe:45
[Parsed_blackframe_0 @ 00000238859ba1c0] frame:46 pblack:100 pts:46 t:1.840000 type:I last_keyframe:46
Basically I need to check if the first and last frame of the file are black. Is it possible to get and parse this list with FFAStrans?
UPD:
Ok, it actually works, I should have put the -sseof -1 BEFORE the -i option... Sorry, false alarm:
Code: Select all
ffmpeg -sseof -1 -i "D:\RENDER\test_black.avi" -vf "blackframe=thresh=32:amount=50" -an -f null - 2>&1 | findstr "Parsed_blackframe" >> "blacks.txt"
Works beautifully, thanks!
Re: Detect 1 sec black at the end of files
Posted: Fri Feb 10, 2023 9:47 am
by emcodem
movalex wrote: ↑Thu Feb 09, 2023 6:39 pm
Ok, it actually works, I should have put the -sseof -1 BEFORE the -i option...
Yeey, congrats on getting it working
And thanks for the response!
It is possible that it don't work exactly with -sseof (before -i) but in that case ffmepg is not able to seek in the container. But i guess such file formats are not subject to be sources for this kind of professional operations and they should be normalized to professional formats anyways.
Re: Detect 1 sec black at the end of files
Posted: Sat Feb 11, 2023 12:26 am
by Conniver
Is there any example workflows or resources where I can find info about checking tech specs with the tools available to FFastrans?
I've managed to create a decent proxy generating workflow (thanks emcodem), and next on the list is a QC / tech spec workflow.
Re: Detect 1 sec black at the end of files
Posted: Sat Feb 11, 2023 7:16 am
by emcodem
@Conniver that's definitely worth another thread
It's like no, we don't have anything in general and there is much possibilities. It depends on what you plan to do. E.g. Simple basic values checking like width, height, bitrate, audio layout... well we got inbuilt variables, functions and a conditional processor for that
Also, for very specialized XDCAM compliance error i had this example:
viewtopic.php?f=5&t=1270&p=6881&hilit=silicon#p6881