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[Spca50x-devs] Need Help: Number_of_Image Data Bytes_Clarification


I am trying to interface a webcam to AVR USB Microcontroller. The webcam is having an SPCA561 bridge,

I try snooping the image data while connecting the webcam to PC, then i am getting image data as Isochronous packets.

There are 32 Isochronous packets of 896 bytes each obtained in one stretch, out of which there are

1) some NULL packets [First Byte 0xFF]

2) A start of frame packet [First Byte 0x00]

3) Then another 22 packets [First byte 0x01 to 0x16]

4) In between random occurrence of NULL packets [First Byte 0xFF]

5) After the last packet [First byte 0x16] the start of frame packet [First Byte 0x00] re-appears.

Which means the valid bytes for a FRAME = 23 * 896 bytes = 20608 bytes

But the expected number of bytes for a FRAME
            = Total no of pixels * No.of bytes per pixel
            = [352 * 288] * 3
            = 304128 bytes

                [where resolution = 352 X 288
                compression = RGB 24 , ie 3 bytes per pixel]

Then please explain how the full image[304128 bytes] is produced from just 20608 bytes..!!
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