Problem with em28xx card, PAL and teletext

Problem with em28xx card, PAL and teletext

[Eugeniy Meshcheryakov]

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Hello,

I have a Pinnacle Hybrid Pro Stick (in kernel source "Pinnacle Hybrid
Pro (2)", driver em28xx). Several kernel releases ago it started to have
problem displaying analog tv correctly. The picture is shifted and
there is green line on the bottom (see http://people.debian.org/~eugen/tv.png).
Also part of the picture is shifted from the right edge to the left
(several columns). TV norm is PAL-BG. I noticed that teletext is also
not correct. I can see some full words, but text itself is not readable.
Picture is correct if i load em28xx with disable_vbi=1.

Please CC me in replies.

Regards,
Eugeniy Meshcheryakov

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Re: Problem with em28xx card, PAL and teletext

[Devin Heitmueller]

On Wed, Mar 17, 2010 at 10:59 AM, Eugeniy Meshcheryakov
<eugen@debian.org> wrote:
> Hello,
>
> I have a Pinnacle Hybrid Pro Stick (in kernel source "Pinnacle Hybrid
> Pro (2)", driver em28xx). Several kernel releases ago it started to have
> problem displaying analog tv correctly. The picture is shifted and
> there is green line on the bottom (see http://people.debian.org/~eugen/tv.png).
> Also part of the picture is shifted from the right edge to the left
> (several columns). TV norm is PAL-BG. I noticed that teletext is also
> not correct. I can see some full words, but text itself is not readable.
> Picture is correct if i load em28xx with disable_vbi=1.
>
> Please CC me in replies.
>
> Regards,
> Eugeniy Meshcheryakov

The green line is because in order to add the VBI support I had to
crop a few lines off of the active video area at the top.  I've
actually made some additional improvements in this area on a
development tree which I am preparing to submit upstream.  Most
applications such as tvtime crop the area in question (around 1.5% on
all edges) to behave comparably to a television, which results in
users not seeing the top and bottom couple of lines.

The teletext should be working (it was tested against a live source).
Which application are you using?  It's been my experience that the
application support for VBI could be described as "crappy at best", so
it wouldn't surprise me to find that there is an application level
issue.

Devin


-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

Re: Problem with em28xx card, PAL and teletext

[Eugeniy Meshcheryakov]

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Hi,

I was waiting with reply to look at improvements you made in the driver.
But the problem did not go away. Actually it became worser. In recent
kernels the picture is not only shifted, but amount of shift changes
with the time. Every second or so picture is shifted 1-2 pixels right
or left. This problem is introduced with this patch:

   V4L/DVB: em28xx: rework buffer pointer tracking for offset to start of video
   5fee334039550bdd5efed9e69af7860a66a9de37

After reverting this patch the picture does not move anymore. Also there
is still green line on the bottom, and still some pixels that should be
on the right edge are on the left edge.

I'm using mplayer to watch tv. If it helps, it is cable tv in Germany.
Some maplyer parameters related to tv:
norm=pal-bg:device=/dev/video1:tdevice=/dev/vbi0:width=640:height=480:alsa=yes:adevice=hw.2,0:amode=1:immediatemode=0:audiorate=48000

Regards,
Eugeniy Meshcheryakov

17 березня 2010 о 11:43 -0400 Devin Heitmueller написав(-ла):
> On Wed, Mar 17, 2010 at 10:59 AM, Eugeniy Meshcheryakov
> <eugen@debian.org> wrote:
> > Hello,
> >
> > I have a Pinnacle Hybrid Pro Stick (in kernel source "Pinnacle Hybrid
> > Pro (2)", driver em28xx). Several kernel releases ago it started to have
> > problem displaying analog tv correctly. The picture is shifted and
> > there is green line on the bottom (see http://people.debian.org/~eugen/tv.png).
> > Also part of the picture is shifted from the right edge to the left
> > (several columns). TV norm is PAL-BG. I noticed that teletext is also
> > not correct. I can see some full words, but text itself is not readable.
> > Picture is correct if i load em28xx with disable_vbi=1.
> >
> > Please CC me in replies.
> >
> > Regards,
> > Eugeniy Meshcheryakov
> 
> The green line is because in order to add the VBI support I had to
> crop a few lines off of the active video area at the top.  I've
> actually made some additional improvements in this area on a
> development tree which I am preparing to submit upstream.  Most
> applications such as tvtime crop the area in question (around 1.5% on
> all edges) to behave comparably to a television, which results in
> users not seeing the top and bottom couple of lines.
> 
> The teletext should be working (it was tested against a live source).
> Which application are you using?  It's been my experience that the
> application support for VBI could be described as "crappy at best", so
> it wouldn't surprise me to find that there is an application level
> issue.
> 
> Devin
> 
> 
> -- 
> Devin J. Heitmueller - Kernel Labs
> http://www.kernellabs.com

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Re: Problem with em28xx card, PAL and teletext

[Devin Heitmueller]

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On Sun, Jun 13, 2010 at 11:09 AM, Eugeniy Meshcheryakov
<eugen@debian.org> wrote:
> Hi,
>
> I was waiting with reply to look at improvements you made in the driver.
> But the problem did not go away. Actually it became worser. In recent
> kernels the picture is not only shifted, but amount of shift changes
> with the time. Every second or so picture is shifted 1-2 pixels right
> or left. This problem is introduced with this patch:
>
>   V4L/DVB: em28xx: rework buffer pointer tracking for offset to start of video
>   5fee334039550bdd5efed9e69af7860a66a9de37
>
> After reverting this patch the picture does not move anymore. Also there
> is still green line on the bottom, and still some pixels that should be
> on the right edge are on the left edge.
>
> I'm using mplayer to watch tv. If it helps, it is cable tv in Germany.
> Some maplyer parameters related to tv:
> norm=pal-bg:device=/dev/video1:tdevice=/dev/vbi0:width=640:height=480:alsa=yes:adevice=hw.2,0:amode=1:immediatemode=0:audiorate=48000
>
> Regards,
> Eugeniy Meshcheryakov

Hello Eugeniy,

I finally found a couple of hours to debug this issue.  Please try the
attached patch and report back whether it addresses the problem you
were seeing with the fields shifting left/right.

Regarding the green lines at the bottom, this is an artifact of the
VBI changes, resulting from the fact that there is some important VBI
content inside of the Active Video area (line 23 WSS in particular),
and the chip cannot handle providing it both in YUYV format for the
video area as well as in 8 bit greyscale for the VBI.  As a result, we
had to drop the lines from the video area.

What probably needs to happen is I will need to change the driver to
inject black lines into each field to make up for the two lines per
field we're not sending in the video area.  In the meantime though,
you can work around the issue by cropping out the lines with the
following command:

/usr/bin/mplayer -vo xv,x11 tv:// -tv
driver=v4l2:device=/dev/video0:norm=PAL:width=720:height=576:input=1
-vf crop=720:572:0:0

(in particular, look at the "-vf crop=720:572:0:0" portion)

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

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Fix case where fields were not at the correct start location.

From: Devin Heitmueller <dheitmueller@kernellabs.com>

This patch address an arithmetic error for the case where the only remaining
content in the USB packet was the "225Axxxx" start of active video.  In cases
where that happened to be at the end of the frame, we would inject it into the
videobuf (which is incorrect).  This caused fields to be intermittently
rendered off by two pixels.

Thanks to Eugeniy Meshcheryakov for bringing this issue to my attention

Priority: high

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Cc: Eugeniy Meshcheryakov <eugen@debian.org>

diff -r b594029d762f linux/drivers/media/video/em28xx/em28xx-video.c
--- a/linux/drivers/media/video/em28xx/em28xx-video.c	Thu May 13 16:59:15 2010 -0300
+++ b/linux/drivers/media/video/em28xx/em28xx-video.c	Sun Jun 13 15:42:27 2010 -0400
@@ -684,12 +684,12 @@
 		}
 
 		if (buf != NULL && dev->capture_type == 2) {
-			if (len > 4 && p[0] == 0x88 && p[1] == 0x88 &&
+			if (len >= 4 && p[0] == 0x88 && p[1] == 0x88 &&
 			    p[2] == 0x88 && p[3] == 0x88) {
 				p += 4;
 				len -= 4;
 			}
-			if (len > 4 && p[0] == 0x22 && p[1] == 0x5a) {
+			if (len >= 4 && p[0] == 0x22 && p[1] == 0x5a) {
 				em28xx_isocdbg("Video frame %d, len=%i, %s\n",
 					       p[2], len, (p[2] & 1) ?
 					       "odd" : "even");

Re: Problem with em28xx card, PAL and teletext

[Eugeniy Meshcheryakov]

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Hi,

13 червня 2010 о 15:46 -0400 Devin Heitmueller написав(-ла):
> I finally found a couple of hours to debug this issue.  Please try the
> attached patch and report back whether it addresses the problem you
> were seeing with the fields shifting left/right.
Thanks, that patch fixes the shifting problem, all the pixels are in the
right place.

> Regarding the green lines at the bottom, this is an artifact of the
> VBI changes, resulting from the fact that there is some important VBI
> content inside of the Active Video area (line 23 WSS in particular),
> and the chip cannot handle providing it both in YUYV format for the
> video area as well as in 8 bit greyscale for the VBI.  As a result, we
> had to drop the lines from the video area.
> 
> What probably needs to happen is I will need to change the driver to
> inject black lines into each field to make up for the two lines per
> field we're not sending in the video area.
Anything that makes the picture centered will be great.

> In the meantime though,
> you can work around the issue by cropping out the lines with the
> following command:
> 
> /usr/bin/mplayer -vo xv,x11 tv:// -tv
> driver=v4l2:device=/dev/video0:norm=PAL:width=720:height=576:input=1
> -vf crop=720:572:0:0
Thanks for the tip. It worked with 640x480. But when I tried to use
720x576 I got a picture with a lot of noise made of horizontal white
lines. However maybe it is because of damaged USB connector...

Also teletext is still unreadable (both with 640x480 and 720x576). Does
mplayer support teletext correctly? And can it work with resolution
640x480?

Regards,
Eugeniy Meshcheryakov

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Re: Problem with em28xx card, PAL and teletext

[Devin Heitmueller]

On Sun, Jun 13, 2010 at 11:21 PM, Eugeniy Meshcheryakov
<eugen@debian.org> wrote:
> Thanks, that patch fixes the shifting problem, all the pixels are in the
> right place.

Ok, I'll issue a PULL request to get that upstream.  Thanks for testing.

>> In the meantime though,
>> you can work around the issue by cropping out the lines with the
>> following command:
>>
>> /usr/bin/mplayer -vo xv,x11 tv:// -tv
>> driver=v4l2:device=/dev/video0:norm=PAL:width=720:height=576:input=1
>> -vf crop=720:572:0:0
> Thanks for the tip. It worked with 640x480. But when I tried to use
> 720x576 I got a picture with a lot of noise made of horizontal white
> lines. However maybe it is because of damaged USB connector...

If you email me a screenshot (preferably off list due to the size), I
can probably provide some additional advice.  Also please provide the
exact mplayer command you used so I can try to reproduce it here.

> Also teletext is still unreadable (both with 640x480 and 720x576). Does
> mplayer support teletext correctly? And can it work with resolution
> 640x480?

I don't know how good mplayer's teletext support is.  When I did the
original work, I did the testing using "mtt", and in fact I had to do
it over an SSH link since I didn't have a teletext feed here.  It
should work at 640x480 though.

I would suggest you try it with mtt/tvtime at 720x576 and see if it
works.  If it does, then we have a starting point to narrow down
whether it's an issue with the application, the selected capture
resolution, the driver itself, or something strange about the teletext
feed itself.

Cheers,

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

Re: Problem with em28xx card, PAL and teletext

[Eugeniy Meshcheryakov]

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Hello Devin,

14 червня 2010 о 10:19 -0400 Devin Heitmueller написав(-ла):
> > Thanks for the tip. It worked with 640x480. But when I tried to use
> > 720x576 I got a picture with a lot of noise made of horizontal white
> > lines. However maybe it is because of damaged USB connector...
> 
> If you email me a screenshot (preferably off list due to the size), I
> can probably provide some additional advice.  Also please provide the
> exact mplayer command you used so I can try to reproduce it here.
The lines do not look white for me now, it is probably depends on
picture. You can see screenshots here:
http://people.debian.org/~eugen/em28xx/

I had the following in mplayer config file:
ao=alsa
vo=xv
framedrop=1
panscan=0
tv=width=640:height=480:norm=pal-bg:device=/dev/video1:tdevice=/dev/vbi0:alsa=yes:adevice=hw.2,0:amode=1:immediatemode=0:audiorate=48000:chanlist=europe-west:channels=<long list of channels>
lavdopts=threads=2
vf=yadif=0,screenshot=1

Regards,
Eugeniy Meshcheryakov

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