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/* Copyright (C) 2005 Ole Andr� Vadla Ravn�s <oleavr@gmail.com>
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#include "mimic-private.h"
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static gboolean decode(MimCtx *ctx, gboolean is_pframe);
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* Decode a MIMIC-encoded frame into RGB data.
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* @param ctx the mimic context
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* @param input_buffer buffer containing the MIMIC-encoded frame to decode
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* @param output_buffer buffer that will receive the decoded frame in RGB 24-bpp packed pixel top-down format
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* (use #mimic_get_property to determine the required buffer size, as well as frame width and height)
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* @returns #TRUE on success
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gboolean mimic_decode_frame(MimCtx *ctx,
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const guchar *input_buffer,
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guchar *output_buffer)
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gboolean result, is_pframe;
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guchar *input_y, *input_cr, *input_cb;
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if (ctx == NULL || input_buffer == NULL || output_buffer == NULL)
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if (!ctx->decoder_initialized)
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* Get frame dimensions.
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width = GUINT16_FROM_LE(*((guint16 *) (input_buffer + 4)));
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height = GUINT16_FROM_LE(*((guint16 *) (input_buffer + 6)));
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* Resolution changing is not supported.
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if (width != ctx->frame_width ||
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height != ctx->frame_height)
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* Increment frame counter.
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ctx->quality = GUINT16_FROM_LE(*((guint16 *) (input_buffer + 2)));
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is_pframe = GUINT32_FROM_LE(*((guint32 *) (input_buffer + 12)));
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ctx->num_coeffs = input_buffer[16];
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ctx->data_buffer = (gchar *) (input_buffer + 20);
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ctx->cur_chunk_len = 16;
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ctx->read_odd = FALSE;
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if (!(is_pframe && ctx->prev_frame_buf == NULL))
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result = decode(ctx, is_pframe);
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* Perform YUV 420 to RGB conversion.
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input_y = ctx->cur_frame_buf;
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input_cr = ctx->cur_frame_buf + ctx->y_size;
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input_cb = ctx->cur_frame_buf + ctx->y_size + ctx->crcb_size;
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* Main decoding loop.
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static gboolean decode(MimCtx *ctx, gboolean is_pframe)
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gint y, x, i, j, chrom_ch, *bptr, base_offset, offset;
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guchar *src, *dst, *p;
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* Clear Cr and Cb planes.
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p = ctx->cur_frame_buf + ctx->y_size;
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memset(p, 128, 2 * ctx->crcb_size);
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for (y = 0; y < ctx->num_vblocks_y; y++) {
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base_offset = ctx->y_stride * 8 * y;
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src = ctx->prev_frame_buf + base_offset;
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dst = ctx->cur_frame_buf + base_offset;
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for (x = 0; x < ctx->num_hblocks_y; x++) {
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/* Check for a change condition in the current block. */
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bit = _read_bits(ctx, 1);
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/* Yes: Is the new content the same as it was in one of
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* the 15 last frames preceding the previous? */
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bit = _read_bits(ctx, 1);
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if (_vlc_decode_block(ctx, dct_block, ctx->num_coeffs) == FALSE) {
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/* Corruped frame, return. */
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_idct_dequant_block(ctx, dct_block, 0);
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for (i = 0; i < 8; i++) {
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offset = ctx->y_stride * i;
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for (j = 0; j < 8; j++) {
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v = (bptr[j] >= 0) ? bptr[j] : 0;
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*(dst + offset + j) = v;
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/* Yes: read the backreference (4 bits) and copy. */
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backref = _read_bits(ctx, 4);
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p = ctx->buf_ptrs[(ctx->ptr_index + backref) % 16];
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p += base_offset + (x * 8);
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for (i = 0; i < 8; i++) {
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offset = ctx->y_stride * i;
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memcpy(dst + offset, p + offset, 8);
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/* No change no worries: just copy from the previous frame. */
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for (i = 0; i < 8; i++) {
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offset = ctx->y_stride * i;
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memcpy(dst + offset, src + offset, 8);
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* Decode Cr and Cb planes.
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for (chrom_ch = 0; chrom_ch < 2; chrom_ch++) {
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base_offset = ctx->y_size + (ctx->crcb_size * chrom_ch);
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for (y = 0; y < ctx->num_vblocks_cbcr; y++) {
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/* The last row of blocks in chrominance for 160x120 resolution
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* is half the normal height and must be accounted for. */
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if (y + 1 == ctx->num_vblocks_cbcr && ctx->frame_height % 16 != 0)
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offset = base_offset + (ctx->crcb_stride * 8 * y);
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src = ctx->prev_frame_buf + offset;
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dst = ctx->cur_frame_buf + offset;
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for (x = 0; x < ctx->num_hblocks_cbcr; x++) {
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/* Check for a change condition in the current block. */
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bit = _read_bits(ctx, 1);
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/* Yes: decode it. */
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if (_vlc_decode_block(ctx, dct_block, ctx->num_coeffs) == FALSE) {
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/* Corrupted frame: clear Cr and Cb planes and return. */
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p = ctx->cur_frame_buf + ctx->y_size;
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memset(p, 128, ctx->crcb_size * 2);
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_idct_dequant_block(ctx, dct_block, 1);
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for (i = 0; i < num_rows; i++) {
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p = dst + (ctx->crcb_stride * i);
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for (j = 0; j < 8; j++)
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p[j] = dct_block[(i * 8) + j];
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/* No change no worries: just copy from the previous frame. */
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for (i = 0; i < num_rows; i++) {
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offset = ctx->crcb_stride * i;
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memcpy(dst + offset, src + offset, 8);
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* Make a copy of the current frame and store in
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* the circular pointer list of 16 entries.
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ctx->prev_frame_buf = ctx->buf_ptrs[ctx->ptr_index];
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memcpy(ctx->prev_frame_buf, ctx->cur_frame_buf,
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ctx->y_size + (ctx->crcb_size * 2));
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if (--ctx->ptr_index < 0)
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* Perform deblocking on all planes.
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_deblock(ctx->cur_frame_buf,
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ctx->y_stride, ctx->y_row_count);
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_deblock(ctx->cur_frame_buf + ctx->y_size,
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ctx->crcb_stride, ctx->crcb_row_count);
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_deblock(ctx->cur_frame_buf + ctx->y_size + ctx->crcb_size,
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ctx->crcb_stride, ctx->crcb_row_count);
added
removed
utils/webcamsn/src/decode.c
