Bugreport for libv4l: error out on webcam: error parsing JPEG header: Bogus jpeg format

Bugreport for libv4l: error out on webcam: error parsing JPEG header: Bogus jpeg format

[Yuri]

I use Logitech QuickCam Deluxe on FreeBSD-8.1.

It shows the image for a while but after 20sec-5min it errors out with 
the message from libv4l, see below.

Could this be a bug in libv4l or it maybe it should be passed some 
tolerance to errors option?

--- log ---
 > pwcview -s vga
Webcam set to: 640x480 (vga) at 5 fps
libv4l2: error converting / decoding frame data: v4l-convert: error 
parsing JPEG header: Bogus jpeg format


Error reading from webcam: Input/output error

Re: Bugreport for libv4l: error out on webcam: error parsing JPEG header: Bogus jpeg format

[Hans de Goede]

Hi,

On 07/15/2010 09:30 PM, Yuri wrote:
> I use Logitech QuickCam Deluxe on FreeBSD-8.1.
>
> It shows the image for a while but after 20sec-5min it errors out with
> the message from libv4l, see below.
>
> Could this be a bug in libv4l or it maybe it should be passed some
> tolerance to errors option?
>

This is not really a bug in libv4l, but more of a problem with error
tolerance in the application you are using. However many apps don't handle
any kind of errors all that well. So the latest libv4l will retry (get a new
frame) jpeg decompression errors a number of times.

I'll send you a mail with instructions how to install the latest libv4l.
The instructions are tailored for people who have an upside down mounted
webcam in their laptop (as that is what I get the most reports about), but
should work fine for you too :)

Regards,

Hans

Re: Bugreport for libv4l: error out on webcam: error parsing JPEG header: Bogus jpeg format

[Yuri]

On 07/19/2010 05:22, Hans de Goede wrote:
> This is not really a bug in libv4l, but more of a problem with error
> tolerance in the application you are using. However many apps don't 
> handle
> any kind of errors all that well. So the latest libv4l will retry (get 
> a new
> frame) jpeg decompression errors a number of times.

You are right, application is quite rough and doesn't have any tolerance.

But why such bad bytes appear in the first place? I think they are sent 
by the
camera deliberately to indicate something and Windows driver must be knowing
what do they mean. But libv4l just can't interpret them correctly.

Yuri

Re: Bugreport for libv4l: error out on webcam: error parsing JPEG header: Bogus jpeg format

[Hans de Goede]

Hi,

On 07/19/2010 06:53 PM, Yuri wrote:
> On 07/19/2010 05:22, Hans de Goede wrote:
>> This is not really a bug in libv4l, but more of a problem with error
>> tolerance in the application you are using. However many apps don't
>> handle
>> any kind of errors all that well. So the latest libv4l will retry (get
>> a new
>> frame) jpeg decompression errors a number of times.
>
> You are right, application is quite rough and doesn't have any tolerance.
>
> But why such bad bytes appear in the first place? I think they are sent
> by the
> camera deliberately to indicate something and Windows driver must be
> knowing
> what do they mean.

That is not very likely as they are in the middle of the jpeg data stream
(special bytes would normally be in the header or footer of each frame).

Most likely the cause is a not 100% usb connection, or some subtle linux
driver bug causing this.

Regards,

Hans