v4l2_libs/libv4lconvert/sn9c10x.c

/*
# sonix decoder
#               Bertrik.Sikken. (C) 2005

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License, version 2.1,
# as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335  USA

# Note this code was originally licensed under the GNU GPL instead of the
# GNU LGPL, its license has been changed with permission, see the permission
# mail at the end of this file.
 */

#include "libv4lconvert-priv.h"

#define CLAMP(x)	((x) < 0 ? 0 : ((x) > 255) ? 255 : (x))

struct code_table {
	int is_abs;
	int len;
	int val;
	int unk;
};


/* local storage */
/* FIXME not thread safe !! */
static struct code_table table[256];
static int init_done;

/*
   sonix_decompress_init
   =====================
   pre-calculates a locally stored table for efficient huffman-decoding.

   Each entry at index x in the table represents the codeword
   present at the MSB of byte x.

 */
static void sonix_decompress_init(void)
{
	int i;
	int is_abs, val, len, unk;

	for (i = 0; i < 256; i++) {
		is_abs = 0;
		val = 0;
		len = 0;
		unk = 0;
		if ((i & 0x80) == 0) {
			/* code 0 */
			val = 0;
			len = 1;
		} else if ((i & 0xE0) == 0x80) {
			/* code 100 */
			val = 4;
			len = 3;
		} else if ((i & 0xE0) == 0xA0) {
			/* code 101 */
			val = -4;
			len = 3;
		} else if ((i & 0xF0) == 0xD0) {
			/* code 1101 */
			val = 11;
			len = 4;
		} else if ((i & 0xF0) == 0xF0) {
			/* code 1111 */
			val = -11;
			len = 4;
		} else if ((i & 0xF8) == 0xC8) {
			/* code 11001 */
			val = 20;
			len = 5;
		} else if ((i & 0xFC) == 0xC0) {
			/* code 110000 */
			val = -20;
			len = 6;
		} else if ((i & 0xFC) == 0xC4) {
			/* code 110001xx: unknown */
			val = 0;
			len = 8;
			unk = 1;
		} else if ((i & 0xF0) == 0xE0) {
			/* code 1110xxxx */
			is_abs = 1;
			val = (i & 0x0F) << 4;
			len = 8;
		}
		table[i].is_abs = is_abs;
		table[i].val = val;
		table[i].len = len;
		table[i].unk = unk;
	}

	init_done = 1;
}


/*
   sonix_decompress
   ================
   decompresses an image encoded by a SN9C101 camera controller chip.

   IN	width
   height
   inp		pointer to compressed frame (with header already stripped)
   OUT	outp	pointer to decompressed frame

   Returns 0 if the operation was successful.
   Returns <0 if operation failed.

 */
void v4lconvert_decode_sn9c10x(const unsigned char *inp, unsigned char *outp,
		int width, int height)
{
	int row, col;
	int val;
	int bitpos;
	unsigned char code;
	const unsigned char *addr;

	if (!init_done)
		sonix_decompress_init();

	bitpos = 0;
	for (row = 0; row < height; row++) {
		col = 0;

		/* first two pixels in first two rows are stored as raw 8-bit */
		if (row < 2) {
			addr = inp + (bitpos >> 3);
			code = (addr[0] << (bitpos & 7)) | (addr[1] >> (8 - (bitpos & 7)));
			bitpos += 8;
			*outp++ = code;

			addr = inp + (bitpos >> 3);
			code = (addr[0] << (bitpos & 7)) | (addr[1] >> (8 - (bitpos & 7)));
			bitpos += 8;
			*outp++ = code;

			col += 2;
		}

		while (col < width) {
			/* get bitcode from bitstream */
			addr = inp + (bitpos >> 3);
			code = (addr[0] << (bitpos & 7)) | (addr[1] >> (8 - (bitpos & 7)));

			/* update bit position */
			bitpos += table[code].len;

			/* Skip unknown codes (most likely they indicate
			   a change of the delta's the various codes encode) */
			if (table[code].unk)
				continue;

			/* calculate pixel value */
			val = table[code].val;
			if (!table[code].is_abs) {
				/* value is relative to top and left pixel */
				if (col < 2) {
					/* left column: relative to top pixel */
					val += outp[-2 * width];
				} else if (row < 2) {
					/* top row: relative to left pixel */
					val += outp[-2];
				} else {
					/* main area: average of left pixel and top pixel */
					val += (outp[-2] + outp[-2 * width]) / 2;
				}
			}

			/* store pixel */
			*outp++ = CLAMP(val);
			col++;
		}
	}
}

/*
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Date: Thu, 03 Jul 2008 15:19:53 +0200
From: Bertrik Sikken <bertrik@sikken.nl>
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To: Hans de Goede <j.w.r.degoede@hhs.nl>
Subject: Re: pac207 bayer decompression algorithm license question
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hans de Goede wrote:
| Bertrik Sikken wrote:
|> Hallo Hans,
|>
|> Hans de Goede wrote:
|>> I would like to also add support for decompressing the pac207's
|>> compressed
|>> bayer to this lib (and remove it from the kernel driver) and I've
|>> heard from Thomas Kaiser that you are a co-author of the
|>> decompression code. In order to add support for decompressing pac207
|>> compressed bayer to libv4l I need
|>> permission to relicense the decompression code under the LGPL
|>> (version 2 or later).
|>>
|>> Can you give me permission for this?
|>
|> Ja, vind ik goed.
|>
|
| Thanks!
|
| I'm currently working on adding support for the sn9c10x bayer
| compression to libv4l too, and I noticed this was written by you too.
|
| May I have your permission to relicense the sn9c10x bayer decompression
| code under the LGPL (version 2 or later)?

I hereby grant you permission to relicense the sn9c10x bayer
decompression code under the LGPL (version 2 or later).

Kind regards,
     Bertrik
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	*/