directfb

fbdev · 07-07-2011, 12:53 PM

i am trying to write an application for directfb but it seems unable to switch to 4 bpp mode, the mode required by the e-ink framebuffer to render properly.

it seems to be unable to use LUT4; instead insisting on LUT8.

does anyone know how to either switch the framebuffer to 8 bpp or coerce directfb into a 4 bpp mode?

thanks.

hawhill · 07-07-2011, 03:17 PM

It doesn't even provide a definition of LUT4, does it? So LUT8 is probably all it provides (on API side). Did you check if LUT8 works out of the box? Or maybe what IDirectFB::EnumVideoModes provides?

fbdev · 07-07-2011, 04:50 PM

LUT8 doesn't work.
the framebuffer only has 4bpp, so it ends up rendering everything at 2x magnification with white stripes (from the extra bits) between the lines.
i'm working on forcing A4 by mmap()ing the framebuffer to a surface but it's being....well, a computer about it. :]

fbdev · 07-07-2011, 06:00 PM

what i wanted most was anti-aliased fonts (they're gorgeous with this hack!).
anti-aliasing needs A8 pixel format.
i created a surface:

einkdsc.flags
= DSDESC_CAPS|DSDESC_WIDTH|DSDESC_HEIGHT
|DSDESC_PIXELFORMAT|DSDESC_PREALLOCATED;
einkdsc.caps = 0;
einkdsc.width = 600;
einkdsc.height = 800;
einkdsc.pixelformat = DSPF_A8;
einkdsc.preallocated[0].data = screenbuffer;
einkdsc.preallocated[0].pitch = 600;
einkdsc.preallocated[1].data = screenbuffer;
einkdsc.preallocated[1].pitch = 600;
dfb->CreateSurface(dfb,&einkdsc,&eink);

then mmap()ed the framebuffer:
framebuffer
= mmap(NULL,(800 * 600) / 2,PROT_READ|PROT_WRITE,MAP_SHARED,fb,0);

and i blit between the two:

void fbblit(char* dst,char* src)
{
unsigned aa;
aa = 0;
for(;

{
dst[aa] = ((src[aa * 2] & 0xf) << 4) | (src[1 + (aa * 2)] & 0xf);
dst[aa] ^= 0xff;
++aa;
if(((600 * 800) / 2) == aa) break;
}
}

hawhill · 07-08-2011, 06:23 AM

Hm. I really wonder how the Amazon stack does this. I think I'll put v3 on my Kindle DX this weekend and try myself (2.x firmware doesn't seem to include a ready-built DirectFB). But please update this thread if you stumble upon more information, much appreciated.

geekmaster · 12-16-2011, 09:57 PM

It appears that my kindle 4 (no keyboard) uses 8 bpp. The Touch is probably the same.

07-07-2011, 12:53 PM	#1
fbdev fbdev Posts: 107 Karma: 70177 Join Date: Jul 2011 Device: kindle	directfb i am trying to write an application for directfb but it seems unable to switch to 4 bpp mode, the mode required by the e-ink framebuffer to render properly. it seems to be unable to use LUT4; instead insisting on LUT8. does anyone know how to either switch the framebuffer to 8 bpp or coerce directfb into a 4 bpp mode? thanks.

07-07-2011, 04:50 PM	#3
fbdev fbdev Posts: 107 Karma: 70177 Join Date: Jul 2011 Device: kindle	no LUT4 LUT8 doesn't work. the framebuffer only has 4bpp, so it ends up rendering everything at 2x magnification with white stripes (from the extra bits) between the lines. i'm working on forcing A4 by mmap()ing the framebuffer to a surface but it's being....well, a computer about it. :]

07-07-2011, 06:00 PM	#4
fbdev fbdev Posts: 107 Karma: 70177 Join Date: Jul 2011 Device: kindle	fixed (kind of) what i wanted most was anti-aliased fonts (they're gorgeous with this hack!). anti-aliasing needs A8 pixel format. i created a surface: einkdsc.flags = DSDESC_CAPS\|DSDESC_WIDTH\|DSDESC_HEIGHT \|DSDESC_PIXELFORMAT\|DSDESC_PREALLOCATED; einkdsc.caps = 0; einkdsc.width = 600; einkdsc.height = 800; einkdsc.pixelformat = DSPF_A8; einkdsc.preallocated[0].data = screenbuffer; einkdsc.preallocated[0].pitch = 600; einkdsc.preallocated[1].data = screenbuffer; einkdsc.preallocated[1].pitch = 600; dfb->CreateSurface(dfb,&einkdsc,&eink); then mmap()ed the framebuffer: framebuffer = mmap(NULL,(800 * 600) / 2,PROT_READ\|PROT_WRITE,MAP_SHARED,fb,0); and i blit between the two: void fbblit(char* dst,char* src) { unsigned aa; aa = 0; for(; { dst[aa] = ((src[aa * 2] & 0xf) << 4) \| (src[1 + (aa * 2)] & 0xf); dst[aa] ^= 0xff; ++aa; if(((600 * 800) / 2) == aa) break; } }

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07-07-2011, 03:17 PM	#2
hawhill Wizard Posts: 1,379 Karma: 2155307 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kobo Mini	It doesn't even provide a definition of LUT4, does it? So LUT8 is probably all it provides (on API side). Did you check if LUT8 works out of the box? Or maybe what IDirectFB::EnumVideoModes provides?

07-08-2011, 06:23 AM	#5
hawhill Wizard Posts: 1,379 Karma: 2155307 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kobo Mini	Hm. I really wonder how the Amazon stack does this. I think I'll put v3 on my Kindle DX this weekend and try myself (2.x firmware doesn't seem to include a ready-built DirectFB). But please update this thread if you stumble upon more information, much appreciated.

12-16-2011, 09:57 PM	#6
geekmaster Carpe diem, c'est la vie. Posts: 6,433 Karma: 10773668 Join Date: Nov 2011 Location: Multiverse 6627A Device: K1 to PW3	It appears that my kindle 4 (no keyboard) uses 8 bpp. The Touch is probably the same.

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