[mythtv] WinTV USB works with mplayer but not with mythtv

Volker Fischer v.fischer at nt.tu-darmstadt.de
Tue Jan 26 18:11:43 UTC 2010


I have an external WinTV USB tv card which works under Ubuntu with 
mplayer but not with mythtv.

Doing some research I found out that the problem is in 
"NuppelVideoRecorder.cpp" in the function "void 
NuppelVideoRecorder::DoV4L2(void)". The number of buffers must always be 
5 ("int numbuffers = 5;" and "if (vrbuf.count < 5)") but with my card 
the call to "ioctl(fd, VIDIOC_REQBUFS, &vrbuf)" results in vrbuf.count 
is equal to 3.

Disabling the buffer length check, I get a segmentation fault in 
"yuyvtoyuv420_MMX2" from "libmythswscale-0.22.so.0". Disabling the line 
"myth_sws_img_convert(&img_out, PIX_FMT_YUV420P, &img_in, 
PIX_FMT_YUYV422, w, h);" resolves the segmentation fault issue but, of 
course, I only get a picture filled with some random noise at the 

Is there an easy way to do the scaling with only 3 buffers? I do not 
really understand whats going on in all these scaling functions so I 
really need some help here.

Thank you in advance for your help, best Regards,

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