libv4l: problem with 2x downscaling + Labtec Webcam 2200

Hello Hans,

I am using your libv4l 0.6.0 [1] together with the driver gspca_pac7311 from Linux kernel 2.6.31-rc4 and with Labtec Webcam 2200 hardware [2]. I am using the svv.c [3] to display the webcam image.

When I'm using the webcam in 640x480 the image is displayed correctly. However, when I set the resolution to 320x240, the image is not correct:
the image contains horizontal lines and doubled vertically. I guess the conversion from 640x480 is not done just the pixels are shown as it would be 320x240.

$ ./svv -f 320x240
raw pixfmt: PJPG 640x480
pixfmt: RGB3 320x240
mmap method

What do you think the problem could be?

References:
[1] libv4l
http://freshmeat.net/projects/libv4l

[2] Labtec Webcam 2200
http://labtec.com/index.cfm/service/listing/EUR/EN,crid=68,crid2=1764

[3] svv.c
http://moinejf.free.fr/svv.c

$ v4l-info

### v4l2 device info [/dev/video0] ###
general info

    VIDIOC_QUERYCAP
        driver                  : "pac7311"
        card                    : "USB Camera (093a:2626)"
        bus_info                : "usb-0000:00:10.1-1"
        version                 : 2.6.0
        capabilities            : 0x5000001 [VIDEO_CAPTURE,READWRITE,STREAMING]

standards

inputs
VIDIOC_ENUMINPUT(0)
index : 0
name : "pac7311"
type : CAMERA
audioset : 0
tuner : 0
std : 0x0 []
status : 0x0 []

video capture
VIDIOC_ENUM_FMT(0,VIDEO_CAPTURE)
index : 0
type : VIDEO_CAPTURE
flags : 0
description : "PJPG"
pixelformat : 0x47504a50 [PJPG]
VIDIOC_G_FMT(VIDEO_CAPTURE)
type : VIDEO_CAPTURE
fmt.pix.width : 640
fmt.pix.height : 480
fmt.pix.pixelformat : 0x47504a50 [PJPG]
fmt.pix.field : NONE
fmt.pix.bytesperline : 640
fmt.pix.sizeimage : 115790
fmt.pix.colorspace : JPEG
fmt.pix.priv : 0

controls
VIDIOC_QUERYCTRL(BASE+0)
id : 9963776
type : INTEGER
name : "Brightness"
minimum : 0
maximum : 32
step : 1
default_value : 16
flags : 0
VIDIOC_QUERYCTRL(BASE+1)
id : 9963777
type : INTEGER
name : "Contrast"
minimum : 0
maximum : 255
step : 1
default_value : 127
flags : 0
VIDIOC_QUERYCTRL(BASE+2)
id : 9963778
type : INTEGER
name : "Saturation"
minimum : 0
maximum : 255
step : 1
default_value : 127
flags : 0

### video4linux device info [/dev/video0] ###
general info
VIDIOCGCAP
name : "USB Camera (093a:2626)"
type : 0x1 [CAPTURE]
channels : 1
audios : 0
maxwidth : 640
maxheight : 480
minwidth : 48
minheight : 32

channels
VIDIOCGCHAN(0)
channel : 0
name : "pac7311"
tuners : 0
flags : 0x0 []
type : CAMERA
norm : 0

tuner
ioctl VIDIOCGTUNER: Invalid argument

audio
VIDIOCGAUDIO
audio : 0
volume : 0
bass : 0
treble : 0

picture
VIDIOCGPICT
brightness : 32768
hue : 0
colour : 32639
contrast : 32639
whiteness : 0
depth : 8
palette : unknown

buffer
ioctl VIDIOCGFBUF: Invalid argument

window
VIDIOCGWIN
x : 0
y : 0
width : 640
height : 480
chromakey : 0
flags : 0

Regards,

Márton Németh

Hi,

This is a known problem in 0.6.0 fixed by this commit:
http://linuxtv.org/hg/~hgoede/libv4l/rev/89fba654c7ea

You can get a snapshot of what will eventually
(soonish) become 0.6.1 here:
http://people.atrpms.net/~hdegoede/libv4l-0.6.1-test.tar.gz

Upgrading to this should fix your problems.

Regards,

Hans

Hello Hans,

Thanks, the libv4l 0.6.1-test fixed the problem for me.

Regards,

Márton Németh