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 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;
}
}
/* decode all macroblocks of the current picture */
static void i_picture(APEG_LAYER *layer)
{
const int MBAmax = layer->mb_cols*layer->mb_rows;
int MBA, MBAinc;
int dc_dct_pred[3];
int bx, by;
unsigned int code;
slice_start:
dc_dct_pred[0] = dc_dct_pred[1] = dc_dct_pred[2] = 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:
switch(show_bits(layer, 2))
{
case 0:
goto slice_start;
case 1:
layer->quantizer_scale = apeg_get_bits(layer, 7) & MASK_BITS(5);
break;
default:
apeg_flush_bits1(layer);
}
apeg_decode_intra_blocks(layer, dc_dct_pred);
apeg_fast_idct(apeg_block[0]);
apeg_fast_idct(apeg_block[1]);
apeg_fast_idct(apeg_block[2]);
apeg_fast_idct(apeg_block[3]);
apeg_fast_idct(apeg_block[4]);
apeg_fast_idct(apeg_block[5]);
Move_Blocks(layer, bx, by);
if(++MBA >= MBAmax)
return;
if(show_bits(layer, 24) == 1)
goto slice_start;
MBAinc = get_mba_inc(layer);
if(MBAinc == 0)
{
if((bx += 16) == layer->coded_width)
{
bx = 0;
by += 16;
}
goto block_start;
}
dc_dct_pred[0] = dc_dct_pred[1] = dc_dct_pred[2] = 0;
MBA += MBAinc;
if(MBA >= MBAmax)
return;
bx = (MBA%layer->mb_cols) << 4;
by = (MBA/layer->mb_cols) << 4;
goto block_start;
}