The '-vcodec copy' option is nice, but I've had issues using it in
conjunction with trying to set the frame rate for the output media; any
combination of flags attempting to set either the source or destination
frame rates seem to be ignored, and you always end up with a 25 fps output
file.
Also, for what it's worth, using ffmpeg to re-encode a JPEG sequence doesn't
introduce a gamma shift in any scenario I've encountered.
-Nathan
-----Original Message-----
From: Holger Hummel|Celluloid VFX
Sent: Wednesday, May 01, 2013 7:50 AM
To: Nuke user discussion
Subject: Re: [Nuke-users] ffmpeg Photo-JPEG QuickTimes
unfortunately, i don't know how to get around that nasty
gamma/brightness shift either. i'd be more than happy to find the
solution for this.
but there's another option that you can also use to get a Photo-JPEG
Quicktme with the exact jpg quality you want.
you just render out a jpg sequence with the esact setting as you want
from within Nuke and then use ffmpeg's '-vcodec copy' option.
this will just copy/wrap the jpg files into a Quicktime file without
re-encoding - unfortunately including that nasty gamma shift.
Holger
Nathan Rusch wrote:
I ended up writing an movWriter for Linux for this exact reason. I’m not
exactly sure how to translate Quicktime’s “90%” setting into quantizer and
bitrate parameters, but this should at least give you a bitrate and
quality level somewhere in the same neighborhood.
ffmpeg -r 24 -start_number 1001 -i
/path/to/input_sequence.%04d.jpg -pix_fmt yuvj420p -vcodec mjpeg -f
mov -qmin 0 -qmax 1 /path/to/output/file.mov
You need the '-start_number' flag if your sequence starts at a frame
other than 1 or if you only want to use a subset of a sequence. The '-r'
flag sets the frame rate of the source, and since no target rate is
specified, the same will be used for the output. You can also use
'yuvj422p' for the output '-pix_fmt' value if you want 4:2:2 chroma
subsampling.
Hope this helps.
-Nathan
*From:* Dan Rosen <mailto:[email protected]>
*Sent:* Tuesday, April 30, 2013 4:49 PM
*To:* Foundry <mailto:[email protected]>
*Subject:* [Nuke-users] ffmpeg Photo-JPEG QuickTimes
Hello,
Sorry to use this forum, but hopefully someone can point me in the right
direction to use ffmpeg (given that Nuke cannot properly write out a
Photo-JPEG QuickTime with correct color nor with 90% quality). I am trying
to write out frames from Nuke, with the lut applied in Nuke, and then
compile them into Photo-JPEG QuickTime with 90% quality. There's a
brightness shift that appears to be the pesky gama atom, but the file does
not actually contain the atom so there's no solid way to remove the shift.
I am still testing so the shift maybe something else. Fwiw, I have found
good results with the ProRes codec (no shift).
I have read up on the it online, but all results list "mpeg" as the
format in the Inspector window of QuickTime, but maybe it's correct since
it lists "Photo-Jpeg" in the format int the Properties window.
Any help would be much appreciated. Thanks!
-Dan
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--
Holger Hummel - [email protected]
Celluloid Visual Effects GmbH & Co. KG
Paul-Lincke-Ufer 39/40, 10999 Berlin
phone +49 (0)30 / 54 735 220 - [email protected]
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