From: Kirill Smelkov Date: Mon, 13 Jun 2011 12:18:32 +0000 (+0400) Subject: staging/easycap: Fix bytesperline calculation X-Git-Tag: next-20110726~5^2~231 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=378af483331d429bff3318e69f4ff5534f92c750;p=karo-tx-linux.git staging/easycap: Fix bytesperline calculation As described above fillin_formats() """ /* * THE 16-BIT easycap_format.mask HAS MEANING: * (least significant) BIT 0: 0 => PAL, 25 FPS; 1 => NTSC, 30 FPS * BITS 2-4: RESERVED FOR DIFFERENTIATING STANDARDS * BITS 5-7: NUMBER OF BYTES PER PIXEL * BIT 8: 0 => NATIVE BYTE ORDER; 1 => SWAPPED * BITS 9-10: RESERVED FOR OTHER BYTE PERMUTATIONS * BIT 11: 0 => UNDECIMATED; 1 => DECIMATED * BIT 12: 0 => OFFER FRAMES; 1 => OFFER FIELDS * BIT 13: 0 => FULL FRAMERATE; 1 => REDUCED * (most significant) BITS 14-15: RESERVED FOR OTHER FIELD/FRAME OPTIONS * IT FOLLOWS THAT: * bytesperpixel IS ((0x00E0 & easycap_format.mask) >> 5) * byteswaporder IS true IF (0 != (0x0100 & easycap_format.mask)) * * decimatepixel IS true IF (0 != (0x0800 & easycap_format.mask)) * * offerfields IS true IF (0 != (0x1000 & easycap_format.mask)) */ """ bytes-per-pixel is stored in bits 5-7 of calculated mask. But when calculating bytes-per-line we were extracting wrong value instead of bytes-per-pixel, which was usually 2 times bigger -- e.g. for PAL YUV 422 I was getting ((mask3 & 0x00F0) >> 4) = 4 bytes instead of 2. The error here is that even in comments there is a line saying * bytesperpixel IS ((0x00E0 & easycap_format.mask) >> 5) but we were using ((0x00F0 & easycap_format.mask) >> 4) With 2 times bigger bytesperpixel and automatically bytesperline, the video was shown halfheight'ed, which is understandable if we look at video-memory layout: <------- bytesperline --------> <- real bpl -> x0----------y0 x1-----------y1 x2----------y2 x3-----------y3 xn----------yn xn-----------yn for each line, we should display width pixels, then move to next line with bytesperline, and oops, if bytesperline = 2*real-bytesperlin, we'll skip one line and move to next-next line, and so only half lines will be shown. Initially I've debugged the problem with my video application[1], but I've checked that after this patch both rawv (mine app) and tvtime work correctly. [1] http://repo.or.cz/w/rawv.git P.S. why at all we use those mask/shifts? Why not use bitfields? Cc: Mike Thomas Signed-off-by: Kirill Smelkov Acked-by: Tomas Winkler Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/staging/easycap/easycap_settings.c b/drivers/staging/easycap/easycap_settings.c index 898559dad704..70f59b13c34d 100644 --- a/drivers/staging/easycap/easycap_settings.c +++ b/drivers/staging/easycap/easycap_settings.c @@ -567,7 +567,7 @@ int fillin_formats(void) default: return -3; } - bytesperline = width * ((mask3 & 0x00F0) >> 4); + bytesperline = width * ((mask3 & 0x00E0) >> 5); sizeimage = bytesperline * height; for (m = 0; m < INTERLACE_MANY; m++) {