93 lines
1.8 KiB
C++
93 lines
1.8 KiB
C++
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#include "Decoder.h"
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/*
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* decode headers from one input stream
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* until an End of Sequence or picture start code
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* is found
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*/
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int Decoder::getheader()
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{
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unsigned int sorenson_version;
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/* look for startcode */
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startcode();
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buffer.getbits(PSC_LENGTH);
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sorenson_version = buffer.getbits(5);
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if (sorenson_version <= 1)
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{
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escapemode=sorenson_version;
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getpicturehdr();
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}
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else
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return 0;
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return 1;
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}
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/* align to start of next startcode */
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void Decoder::startcode()
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{
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/* search for new picture start code */
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while (buffer.showbits(PSC_LENGTH)!=1l)
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buffer.flushbits(1);
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}
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/* decode picture header */
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void Decoder::getpicturehdr()
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{
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int pei, tmp;
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buffer.getbits(8);
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tmp = buffer.getbits(3);
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switch(tmp)
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{
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case 0:
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horizontal_size = buffer.getbits(8);
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vertical_size = buffer.getbits(8);
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break;
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case 1:
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horizontal_size = buffer.getbits(16);
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vertical_size = buffer.getbits(16);
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break;
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case 2:
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horizontal_size = 352;
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vertical_size = 288;
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break;
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case 3:
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horizontal_size = 176;
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vertical_size = 144;
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break;
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case 4:
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horizontal_size = 128;
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vertical_size = 96;
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break;
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case 5:
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horizontal_size = 320;
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vertical_size = 240;
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break;
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case 6:
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horizontal_size = 160;
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vertical_size = 120;
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break;
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}
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pict_type = buffer.getbits(2);
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deblock=buffer.getbits(1); // deblocking flag
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quant = buffer.getbits(5);
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pei = buffer.getbits(1);
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pspare:
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if (pei) {
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/* extra info for possible future backward compatible additions */
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buffer.getbits(8); /* not used */
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pei = buffer.getbits(1);
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if (pei) goto pspare; /* keep on reading pspare until pei=0 */
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}
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}
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