Re: em28xx: success report for KWORLD DVD Maker USB 2.0 (VS-USB2800) [eb1a:2860]

[Ivan <ivan.q.public@gmail.com>]

On 07/08/2010 04:35 PM, Ivan wrote:
> On 07/08/2010 04:02 PM, Devin Heitmueller wrote:
>> On Thu, Jul 8, 2010 at 3:52 PM, Ivan<ivan.q.public@gmail.com> wrote:
>>> Yep, that gets rid of the vertical stripes but adds in a lovely
>>> horizontal
>>> shift:
>>>
>>> http://www3.picturepush.com/photo/a/3763906/img/3763906.png
>>
>> The "horizontal shift" issue is interesting. Does that happen every
>> time? And did you unplug/replug the device? Try to reboot?
>
> Reboot? What is this, Windoze? :^D
>
> But yeah, it's consistent across unplugs/replugs/reboots.

Ok, the horizontal shift disappears if I switch to 720x480 instead of 
640x480.

Does the card always output 720x480 (in NTSC mode anyway), then, and any 
scaling is done by V4L?

I also have a question about dropped frames. After running mplayer or 
mencoder, I see a line like:

v4l2: 1199 frames successfully processed, -3 frames dropped.

I can only guess that the negative number means that V4L received frames 
at a slightly faster rate than the expected 30000/1001 fps. In my case, 
it would seem that my SNES is producing something more like 30.05 fps, 
and so V4L reports a "negative" dropped frame every 12.5 seconds or so.

It would also seem that V4L doesn't actually discard any frames, but 
still passes them on to mplayer/mencoder, because mencoder shows an 
encoding fps of 30.04 (and it will skip a frame every 12.5 seconds or so 
unless you pass it -noskip).

Am I right about all this?

Ivan