Hi Shashank,
Thanks for the detailed explanation about the relationship between the
aspect-ratio, CEA modes and VIC codes.
I will capture these and try to add this as part of man pages for a
better understanding.
Regards,
Ankit
On 7/3/2018 4:05 PM, Sharma, Shashank wrote:
Regards
Shashank
On 7/3/2018 3:26 PM, Pekka Paalanen wrote:
On Tue, 3 Jul 2018 14:42:06 +0530
"Sharma, Shashank" <shashank.sha...@intel.com> wrote:
Hello Pekka,
Thanks for your attention and code review of the patch series.
Ankit will respond on rest of the review comments, I would take one
related to mode with implicit aspect ratio information.
Please find my comment inline.
Regards
Shashank
On 6/28/2018 7:09 PM, Pekka Paalanen wrote:
On Sun, 20 May 2018 18:33:01 +0530
"Nautiyal, Ankit K" <ankit.k.nauti...@intel.com> wrote:
From: Ankit Nautiyal <ankit.k.nauti...@intel.com>
The flag bits 19-22 of the connector modes, provide the aspect-ratio
information. This information can be stored in flags bits of the
weston mode structure, so that it can used for setting a mode with a
particular aspect-ratio.
Currently, DRM layer supports aspect-ratio with atomic-modesetting by
default. For legacy modeset path, the user-space needs to set the
drm client cap for aspect-ratio, if it wants aspect-ratio information
in modes.
This patch:
- preserves aspect-ratio flags from kernel video modes and
accommodates it in wayland mode.
- uses aspect-ratio to pick the appropriate mode during modeset.
- changes the mode format in configuration file weston.ini to
accommodate aspect-ratio information as:
WIDTHxHEIGHT at REFRESH-RATE ASPECT-RATIO
The aspect-ratio should be given as <length:breadth>.
- modifies the man pages to explain the usage of different mode
format
configurations in weston.ini.
v2: As per recommendation from Pekka Paalanen, Quentin Glidic,
Daniel Stone, dropped the aspect-ratio info from wayland protocol,
thereby avoiding exposure of aspect-ratio to the client.
v3: As suggested by Pekka Paalanen, added aspect_ratio field to store
aspect-ratio information from the drm. Also added drm client
capability for aspect-ratio, as recommended by Daniel Vetter.
v4: Minor modifications and fixes as suggested by Pekka Paalanen.
v5: Rebased, fixed some styling issues, and added aspect-ratio
information while printing weston_modes.
Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
Acked-by: Pekka Paalanen <pekka.paala...@collabora.co.uk> (v4)
---
libweston/compositor-drm.c | 115
+++++++++++++++++++++++++++++++++----
libweston/compositor-drm.h | 21 +++++++
libweston/compositor.h | 1 +
man/weston.ini.man | 13 +++--
4 files changed, 136 insertions(+), 14 deletions(-)
Hi Ankit,
it's been a long while since I last looked at this, so forgive me if I
go in circles with my review comments. I see the aspect ratio bits are
in Linus' RC kernel. I would like to get this merged for the next
release which basically means during the next week if you can.
diff --git a/man/weston.ini.man b/man/weston.ini.man
index f237fd60..e982cac9 100644
--- a/man/weston.ini.man
+++ b/man/weston.ini.man
@@ -371,10 +371,15 @@ The DRM backend accepts different modes:
.PP
.RS 10
.nf
-.BR "WIDTHxHEIGHT " "Resolution size width and height in pixels"
-.BR "preferred " "Uses the preferred mode"
-.BR "current " "Uses the current crt controller mode"
-.BR "off " "Disables the output"
+.BR "WIDTHxHEIGHT " "Resolution size width and
height in pixels"
+.BR "WIDTHxHEIGHT@RR " "Resolution as above and
refresh-rate in Hertz"
+.BR "WIDTHxHEIGHT@RR RATIO " "Resolution as above and
aspect-ratio as length:breadth"
I think the length:breadth could be confusing. H:V? hor:vert? Or
simply
A:B, assuming that aspect ratio is general knowledge.
It would also be worth to list all the acceptable values, because
there
are only few. One cannot give e.g. 8:6 and assume Weston figures
out it
means 4:3. If they are explicitly listed, we could just use RATIO and
not split the value further.
Since these are specific to the DRM-backend, they would be more
logical
in weston-drm.man.
+
+e.g. 720x576@50 4:3, 1920x1080@60 16:9, 2560x1080@60 64:27,
4096x2160@60 256:135 etc.
What is the point of giving the aspect ratio explicitly if the
resolution directly results in the same aspect ratio?
Shouldn't the examples show cases where it actually matters, i.e. when
the display shows non-square pixels? E.g. 1024x768 16:9
The implementation also makes a difference between implicit aspect
ratio (that is, NONE) and explicit aspect ratio even if the two are
equal. Is that intentional? Is there an actual difference?
Yes there is an actual difference, let me try to explain this.
For this, we should first understand difference between CEA-modes Vs
non-CEA-modes. As you might already know, CEA defines timings of a
video
mode, which is considered as standard for HDMI certification and
compliance testing. CEA defines each and every parameter of a video
mode, like h/vactive, h/vfront, h/vback including aspect ratio
information. This unique videmode is given a Video Identification Code
(VIC) which is unique. For example, VIC=4 is 1280x720@60 aspect 16:9.
Hi,
this was new to me, thank you for explaining.
Now, the videomode would be considered a CEA mode, only if it contains
aspect ratio information. In other words:
- 1280x720@60 0:0 is not a CEA mode
- 1280x720@60 16:9 is a CEA mode with VIC=4
But the latter might not be a CEA mode either, if the detailed
parameters are computed with reduced blanking?
Userspace is free to use e.g. CVT to compute a detailed modeline and
also set aspect ratio flags. Will the kernel compare the full detailed
modeline from userspace with the VIC database to find a VIC, or does it
perhaps ignore some bits of the detailed modeline?
Yes, you are right. as kernel compares each video timing parameter, if
Weston picks a VESA reduced blanking mode over a CEA mode, that would
cause a mismatch.
Now, when we apply videomode 1280x720@60 0:0, as this mode timings
doesn't exactly match the CEA information for VIC=4, so would be called
a non-CEA mode. So while setting the HDMI AVI infoframe filed, VIC
parameter will be kept as '0' . But when we apply videomode 1280x720@60
16:9, this matches CEA timings for the mode with VIC=4, so the VIC
information in AVI infoframes would be filled with value 4.
When certification testing is done, in tests like 7-27, the HDMI
analyzer applies a particular CEA mode, and expects the applied mode to
be with exactly same timings, including the aspect ratio and VIC field.
So its important to differentiate between mode with no aspect (NONE)
and
mode with explicit aspect ratio.
I think this is nuanced enough that there should be some documentation
about the difference of modes between with and without aspect ratio in
the man pages for Weston. It was certainly all new to me.
I agree, we can work on adding this documentation about aspect ratios
and their significance to differentiate between videomodes. Ankit, can
you please help here ?
I do wonder if the current modeline behaviour in Weston is good enough.
If user defines a "vague" mode like 1280x720@60 16:9 instead of a
detailed modeline, libweston will search for a compatible mode in the
EDID provided list of video modes. If one is found, it is used, but who
knows if the detailed mode by EDID is actually the VIC mode the user is
wishing for. The only sure way would be to define a detailed modeline
to override EDID. But, I digress. We can talk about choosing a video
modes in another thread if it is an issue.
One good thing is that, in this particular case, while running the
test cases, most of the HDMI analyzers provide one of the following
method:
- They generate EDID on the fly with only 1 mode in it, which is the
CEA test mode. In this way, kernel will register only one mode in the
connector's->modes and userspace would be forced to pick that mode for
modeset.
- They allow a device under test, to run their own utility which can
generate a modeset of a choice, bypassing the UI manager.
I guess in both the cases kernel will parse the test mode, and if
userspace picks a mode from connector;s->modes, it should be good.
But, as you mentioned, in general it's a good idea to refine how to
translate a vague mode of choice from user, into something in kernel's
modedb or monitor's EDID, for example
- If mode is with non-zero aspect ratio, Weston should understand that
its a CEA mode, and search from videomodes in EDID's CEA section
first, than detailed modes.
- If mode is with zero aspect ratio, then we will have to first start
searching from preferred mode/detailed modes and then look for CEA
modes and standard modes.
Probably a separate thread to discus this topic would be a more suitable.
- Shashank
Thanks,
pq
- Shashank
If the kernel or the user defines an aspect ratio that is equal to the
resolution aspect ratio, should we convert the aspect ratio to
WESTON_MODE_PIC_AR_NONE?
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