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3d3215c4e4
Silvercrest mt9v011 sensor produces a 640x480 image. However, previously, the code were getting only half of the lines and merging two consecutive frames to "produce" a 640x480 image. With the addition of progressive mode, now em28xx is working with a full image. However, when the number of lines is bigger than 240, the beginning of some odd lines are filled with blank. After lots of testing, and physically checking the device for a Xtal, it was noticed experimentally that mt9v011 is using em28xx XCLK as its clock. Due to that, changing XCLK value changes the maximum speed of the stream. At the tests, it were possible to produce up to 32 fps, using a 30 MHz XCLK. However, at that rate, the artifacts happen even at 320x240. Lower values of XCLK produces artifacts only at 640x480. At some values of xclk (for example XCLKK = 6 MHz, 640x480), it is possible to see an invalid sucession of artifacts with this pattern: .xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ..xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ...xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ....xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ..xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ...xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx ....xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (where the dots represent the blanked pixels) So, it seems that a waveform in the format of a ramp is interferring at the image. The cause of this interference is currently unknown. Some possibilities are: - electrical interference (maybe this device is broken?); - some issue at mt9v011 programming; - some bug at em28xx chip. So, for now, let's be conservative and use a value of XCLK that we know for sure that it won't cause artifacts. As I'm waiting for more of such devices with different em28xx chipset revisions, I'll have the opportunity to double check the issue with other pieces of hardware. Later patches can vary XCLK depending on the vertical resolutions, if a proper fix is not discovered. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com> |
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