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Today's Topics:
1. Re: Dark / contrasted prepared MJPEG videos (Nicolas Ecarnot)
2. Re: Dark / contrasted prepared MJPEG videos (Herman Robak)
--__--__--
Message: 1
Date: Tue, 10 Jul 2012 21:10:38 +0200
From: Nicolas Ecarnot <nico...@ecarnot.net>
Organization: Si peu...
To: cinelerra@skolelinux.no
Subject: Re: [CinCV] Dark / contrasted prepared MJPEG videos
Reply-To: cinelerra@skolelinux.no
Le 28/06/2012 12:11, Nicolas Ecarnot a =E9crit :
Hi,
Following the advices here :
http://www.g-raffa.eu/Cinelerra/HOWTO/get_media_ready.html
I'm converting with ffmpeg / avconv my input media files to MJPEG files=
.
No obvious quality loss occurs, but they result in darker videos - dark
enough to be noticed. In fact, they are getting darker and/or more
contrasted.
Obviously, once mjpeg-converted, they are well managed by Cinelerra.
I'm a completly newbie regarding to details of colorspace, encoding and
so on.
But when I'm converting, here is what I notice in avconv/ffmpeg output:
> Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selectin=
g
format 'yuvj420p'
This happens only on video that have this yuv420p pix format.
How do I have to understand that?
Is that those files will forever have to get darker when converted?
Is there a way to first convert the pixel format with no color/light
change?
Can ffmpeg/avconv managed other pix formats?
As you can see, I'm a bit lost amongst those notions, and though I'm no=
t
looking for a direct and obvious answer, I'd be glad to be lead to
accurate documentation.
Hi,
I'm sorry to insist on that point, but according to every doc I read=20
related to cinelerra, everyone seems to advice to convert to MJPEG.
This format sounds great to nle software, but I can't figure it out how=20
I can manage this contrast problem.
I'm not clear about whether the fault is on my source files, or a=20
limitation of the MJPEG format, or a limitation of the converter=20
(ffmpeg/avconv).
I'm sure many of you have a well established workflow and you can't live=20
with this issue, so maybe your video source formats don't bother you the=20
way I'm bothered...
--=20
Nicolas Ecarnot
--__--__--
Message: 2
To: cinelerra@skolelinux.no
Subject: Re: [CinCV] Dark / contrasted prepared MJPEG videos
Date: Wed, 11 Jul 2012 11:02:04 +0200
From: "Herman Robak" <her...@skolelinux.no>
Reply-To: cinelerra@skolelinux.no
P=C3=A5 Tue, 10 Jul 2012 21:10:38 +0200, skrev Nicolas Ecarnot <nicolas@=
ecarnot.net>:
Le 28/06/2012 12:11, Nicolas Ecarnot a =C3=A9crit :
Hi,
Following the advices here :
http://www.g-raffa.eu/Cinelerra/HOWTO/get_media_ready.html
I'm converting with ffmpeg / avconv my input media files to MJPEG fil=
es.
No obvious quality loss occurs, but they result in darker videos - da=
rk
enough to be noticed. In fact, they are getting darker and/or more
contrasted.
...
But when I'm converting, here is what I notice in avconv/ffmpeg outpu=
t:
> Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-select=
ing
format 'yuvj420p'
This happens only on video that have this yuv420p pix format.
How do I have to understand that?
...
I'm sorry to insist on that point, but according to every doc I read
related to cinelerra, everyone seems to advice to convert to MJPEG.
This format sounds great to nle software, but I can't figure it out ho=
w
I can manage this contrast problem.
I'm not clear about whether the fault is on my source files, or a
limitation of the MJPEG format, or a limitation of the converter
(ffmpeg/avconv).
I'm sure many of you have a well established workflow and you can't li=
ve
with this issue, so maybe your video source formats don't bother you t=
he
way I'm bothered...
It does bother me, for what it is worth. I think the problem is due to
different luma range (MJPEG is full range; 0-255) and chroma sample alig=
nment.
I'd guess that the contrast range is first stretched, then truncated, le=
ading
to higher contrast _and_ some crushed blacks and clipped highlights.
What to do? Find some other intermediate or proxy format. I'd suggest
DNxHD for intermediates and intra-only low-bitrate h.264 for proxies.
-- =
Herman Robak
--__--__--
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End of Cinelerra Digest
