static void check_stream_type(APEG_LAYER *layer)
{
// Assume a non-system stream
layer->system_stream_flag = NO_SYSTEM;
// Initialize the buffer
_apeg_initialize_buffer(layer);
// Transport streams (what'r those?) aren't supported
if(show_bits(layer, 8) == 0x47)
apeg_error_jump("Transport streams not supported");
/* Get the first start code */
recheck:
switch(show_bits32(layer))
{
case VIDEO_ELEMENTARY_STREAM:
/* Found video, system stream */
layer->system_stream_flag = MPEG_SYSTEM;
/* fall-through; set flag and break */
case SEQUENCE_HEADER_CODE:
/* Found video */
if(!_apeg_ignore_video)
layer->stream.flags |= APEG_MPG_VIDEO;
break;
case AUDIO_ELEMENTARY_STREAM:
/* apeg_start_audio will set APEG_MPG_AUDIO later */
layer->system_stream_flag = MPEG_SYSTEM;
apeg_start_code(layer);
goto recheck;
default:
if(layer->system_stream_flag == NO_SYSTEM)
{
if(show_bits32(layer) == (('O'<<24)|('g'<<16)|('g'<<8)|('S')))
{
layer->system_stream_flag = OGG_SYSTEM;
_apeg_initialize_buffer(layer);
if(alogg_open(layer) != APEG_OK)
apeg_error_jump("Error opening Ogg stream");
return;
}
#ifndef DISABLE_MPEG_AUDIO
if(almpa_head_backcheck(show_bits32(layer)))
break;
#endif
}
/* no positive stream identified; recheck */
apeg_flush_bits8(layer, 8);
goto recheck;
}
_apeg_initialize_buffer(layer);
}
static int Get_Chroma_DC_dct_diff(APEG_LAYER *layer)
{
int code, size;
/* decode length */
code = show_bits(layer, 5);
if (code<31)
{
/* Table B-13, dct_dc_size_chrominance, codes 00xxx ... 11110 */
static const VLCtab DCchromtab0[32] = {
{0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2}, {0, 2},
{1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2}, {1, 2},
{2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2}, {2, 2},
{3, 3}, {3, 3}, {3, 3}, {3, 3}, {4, 4}, {4, 4}, {5, 5}, {0, 0}
};
size = DCchromtab0[code].val;
apeg_flush_bits8(layer, DCchromtab0[code].len);
if(size == 0)
return 0;
}
else
{
/* Table B-13, dct_dc_size_chrominance, codes 111110xxxx ... 1111111111 */
static const VLCtab DCchromtab1[32] = {
{6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, { 6, 6}, { 6, 6},
{6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, {6, 6}, { 6, 6}, { 6, 6},
{7, 7}, {7, 7}, {7, 7}, {7, 7}, {7, 7}, {7, 7}, { 7, 7}, { 7, 7},
{8, 8}, {8, 8}, {8, 8}, {8, 8}, {9, 9}, {9, 9}, {10,10}, {11,10}
};
code = show_bits(layer, 10) - 992;
size = DCchromtab1[code].val;
apeg_flush_bits(layer, DCchromtab1[code].len);
}
{
const int dct_diff = apeg_get_bits(layer, size);
const int f = ((dct_diff >> (size-1))&1)^1;
return dct_diff - ((f<<size) - f);
/* int dct_diff = apeg_get_bits(layer, size);
if (( dct_diff & (1 << (size-1)) ) == 0)
return dct_diff - ((1<<size) - 1);
return dct_diff;*/
}
}
static void p_picture(APEG_LAYER *layer)
{
const int MBAmax = layer->mb_cols*layer->mb_rows;
int macroblock_type;
int coded_block_pattern;
int MBA, MBAinc;
int dc_dct_pred[3];
int PMV[2];
int bx, by;
unsigned int code;
slice_start:
dc_dct_pred[0] = dc_dct_pred[1] = dc_dct_pred[2] = 0;
PMV[0] = PMV[1] = 0;
code = apeg_start_code(layer);
if(code < SLICE_START_CODE_MIN || code > SLICE_START_CODE_MAX)
return;
apeg_flush_bits32(layer);
slice_header(layer);
bx = get_mba_inc(layer);
by = (code&255) - 1;
MBA = by*layer->mb_cols + bx;
bx <<= 4;
by <<= 4;
block_start:
code = show_bits(layer, 6);
if(code >= 8)
{
code >>= 3;
apeg_flush_bits8(layer, PMBtab0[code].len);
macroblock_type = PMBtab0[code].val;
dc_dct_pred[0] = dc_dct_pred[1] = dc_dct_pred[2] = 0;
switch(macroblock_type & (MACROBLOCK_MOTION_FORWARD|MACROBLOCK_PATTERN))
{
case MACROBLOCK_MOTION_FORWARD|MACROBLOCK_PATTERN:
apeg_motion_vector(layer,PMV,forward_code,full_forward_vector);
apeg_form_f_pred(layer, bx, by, PMV);
break;
case MACROBLOCK_PATTERN:
PMV[0] = PMV[1] = 0;
apeg_empty_pred(layer->forward_frame, layer->current_frame, bx, by, layer->coded_width);
break;
default:
apeg_motion_vector(layer,PMV,forward_code,full_forward_vector);
apeg_form_f_pred(layer, bx, by, PMV);
goto next;
}
}
