p64dump.cpp

网络MPEG4IP流媒体开发源代码

	 * start code.
	 */
	int gob;
	for (;;) {
		GET_BITS(bs_, 4, nbb_, bb_, gob);
		if (gob != 0)
			break;
		/*
		 * should happen only on first iteration
		 * (if at all).  pictures always start on
		 * packet boundaries per section 5 of the
		 * Internet Draft.
		 */
		if (parse_picture_hdr() < 0) {
			++bad_fmt_;
			DUMPBITS('\n');
			return (-1);
		}
		/*
		 * Check to see that the next 16 bits
		 * are a start code and throw them away.
		 * But first check that we have the bits.
		 */
		int nbit = ((es_ - bs_) << 4) + nbb_ - ebit;
		if (nbit < 20)
			return (0);

		if (parse_sc() < 0)
			return (-1);
	}
	gob -= 1;
	if (fmt_ == IT_QCIF)
		/*
		 * Number QCIF GOBs 0,1,2 instead of 0,2,4.
		 */
		gob >>= 1;

	int mq;
	GET_BITS(bs_, 5, nbb_, bb_, mq);
	qt_ = &quant_[mq << 8];

	int v;
	GET_BITS(bs_, 1, nbb_, bb_, v);
	printf("gob %d q %d x%d ", gob_, mq, v);
	while (v != 0) {
		GET_BITS(bs_, 9, nbb_, bb_, v);
		v &= 1;
	}
	DUMPBITS('\n');

	gob_ = gob;

	return (gob);
}

/*
 * Parse a macroblock header.  If there is no mb header because
 * we hit the next start code, return -1, otherwise 0.
 */
int P64Dumper::parse_mb_hdr(u_int& cbp)
{
	/*
	 * Read the macroblock address (MBA), throwing
	 * away any prefixed stuff bits.
	 */
	int v;
	HUFF_DECODE(bs_, ht_mba_, nbb_, bb_, v);
	if (v <= 0) {
		if (v == SYM_STUFFBITS) {
			printf("pad ");
			DUMPBITS('\n');
		}
		/*
		 * (probably) hit a start code; either the
		 * next GOB or the next picture header.
		 */
		return (v);
	}

	/*
	 * MBA is differentially encoded.
	 */
	mba_ += v;
	if (mba_ >= MBPERGOB) {
		printf("mba? %d ", mba_);
		DUMPBITS('\n');
		err("mba too big %d", mba_);
		return (SYM_ILLEGAL);
	}

	u_int omt = mt_;
	HUFF_DECODE(bs_, ht_mtype_, nbb_, bb_, mt_);
	printf("mba %d ", mba_);
	if (mt_ & MT_INTRA) 
		printf("intra ");
	if (mt_ & MT_FILTER)
		printf("filter ");
	if (mt_ & MT_MQUANT) {
		int mq;
		GET_BITS(bs_, 5, nbb_, bb_, mq);
		qt_ = &quant_[mq << 8];
		printf("q %d ", mq);
	}
	if (mt_ & MT_MVD) {
		/*
		 * Read motion vector.
		 */
		int dh;
		int dv;
		HUFF_DECODE(bs_, ht_mvd_, nbb_, bb_, dh);
		HUFF_DECODE(bs_, ht_mvd_, nbb_, bb_, dv);
		printf("mv(%d,%d) ", dh, dv);
		/*
		 * Section 4.2.3.4
		 * The vector is differentially coded unless any of:
		 *   - the current mba delta isn't 1
		 *   - the current mba is 1, 12, or 23 (mba mod 11 = 1)
		 *   - the last block didn't have motion vectors.
		 *
		 * This arithmetic is twos-complement restricted
		 * to 5 bits.  XXX this code is broken
		 */
		if ((omt & MT_MVD) != 0 && v == 1 &&
		    mba_ != 0 && mba_ != 11 && mba_ != 22) {
			dh += mvdh_;
			dv += mvdv_;
		}
		mvdh_ = (dh << 27) >> 27;
		mvdv_ = (dv << 27) >> 27;
	}
	/*
	 * Coded block pattern.
	 */
	if (mt_ & MT_CBP) {
		HUFF_DECODE(bs_, ht_cbp_, nbb_, bb_, cbp);
		printf("cbp %02x ", cbp);
		if (cbp > 63) {
			DUMPBITS('\n');
			err("cbp invalid %x", cbp);
			return (SYM_ILLEGAL);
		}
	} else
		cbp = 0x3f;

	DUMPBITS('\n');
	return (1);
}

/*
 * Handle the next block in the current macroblock.
 * If tc is non-zero, then coeffcients are present
 * in the input stream and they are parsed.  Otherwise,
 * coefficients are not present, but we take action
 * according to the type macroblock that we have.
 */
void P64Dumper::decode_block(u_int tc, u_int x, u_int y, u_int stride,
			      u_char* front, u_char* back, int sf, int n)
{
	if (tc != 0)
		printf("blk %d ", n);
	short blk[64];
#ifdef INT_64
	INT_64 mask;
#define MASK_VAL	mask
#define MASK_REF	&mask
#else
	u_int mask[2];
#define MASK_VAL	mask[0], mask[1]
#define MASK_REF	mask
#endif
	if (tc != 0)
		parse_block(blk, MASK_REF);

	int off = y * stride + x;
	u_char* out = front + off;

	if (mt_ & MT_INTRA) {
		if (tc != 0)
			rdct(blk, MASK_VAL, out, stride, (u_char*)0);
		else {
			u_char* in = back + off;
			mvblka(in, out, stride);
		}
		return;
	}
	if ((mt_ & MT_MVD) == 0) {
		u_char* in = back + off;
		if (tc != 0)
			rdct(blk, MASK_VAL, out, stride, in);
		else
			mvblka(in, out, stride);
		return;
	}
	u_int sx = x + (mvdh_ / sf);
	u_int sy = y + (mvdv_ / sf);
	u_char* in = back + sy * stride + sx;
	if (mt_ & MT_FILTER) {
		filter(in, out, stride);
		if (tc != 0)
			rdct(blk, MASK_VAL, out, stride, out);
	} else {
		if (tc != 0)
			rdct(blk, MASK_VAL, out, stride, in);
		else
			mvblk(in, out, stride);
	}
}

/*
 * Decompress the next macroblock.  Return 0 if the macroblock
 * was present (with no errors).  Return SYM_STARTCODE (-1),
 * if there was no macroblock but instead the start of the
 * next GOB or picture (in which case the start code has
 * been consumed).  Return SYM_ILLEGAL (-2) if there was an error.
 */
int P64Dumper::decode_mb()
{
	u_int cbp;
	//register int mba = mba_ + 1;
	register int v;

	if ((v = parse_mb_hdr(cbp)) <= 0)
		return (v);

	/*
	 * Lookup the base coordinate for this MBA.
	 * Convert from a block to a pixel coord.
	 */
	register u_int x, y;
	x = coord_[mba_];
	y = (x & 0xff) << 3;
	x >>= 8;
	x <<= 3;

	/* Update bounding box */
	if (x < minx_)
		minx_ = x;
	if (x > maxx_)
		maxx_ = x;
	if (y < miny_)
		miny_ = y;
	if (y > maxy_)
		maxy_ = y;

	/*
	 * Decode the six blocks in the MB (4Y:1U:1V).
	 * (This code assumes MT_TCOEFF is 1.)
	 */
	register u_int tc = mt_ & MT_TCOEFF;
	register u_int s = width_;
	decode_block(tc & (cbp >> 5), x, y, s, front_, back_, 1, 1);
	decode_block(tc & (cbp >> 4), x + 8, y, s, front_, back_, 1, 2);
	decode_block(tc & (cbp >> 3), x, y + 8, s, front_, back_, 1, 3);
	decode_block(tc & (cbp >> 2), x + 8, y + 8, s, front_, back_, 1, 4);
	s >>= 1;
	int off = size_;
	decode_block(tc & (cbp >> 1), x >> 1, y >> 1, s,
		     front_ + off, back_ + off, 2, 5);
	off += size_ >> 2;
	decode_block(tc & (cbp >> 0), x >> 1, y >> 1, s,
		     front_ + off, back_ + off, 2, 6);

	mbst_[mba_] = MBST_NEW;
	/*
	 * If a marking table was attached, take note.
	 * This allows us to dither only the blocks that have changed,
	 * rather than the entire image on each frame.
	 */
	if (marks_) {
		/* convert to 8x8 block offset */
		off = (x >> 3) + (y >> 3) * (width_ >> 3);
		int m = mark_;
		marks_[off] = m;
		marks_[off + 1] = m;
		off += width_ >> 3;
		marks_[off] = m;
		marks_[off + 1] = m;
	}
	return (0);
}

/*
 * Decode H.261 stream.  Decoding can begin on either
 * a GOB or macroblock header.  All the macroblocks of
 * a given frame can be decoded in any order, but chunks
 * cannot be reordered across frame boundaries.  Since data
 * can be decoded in any order, this entry point can't tell
 * when a frame is fully decoded (actually, we could count
 * macroblocks but if there is loss, we would not know when
 * to sync).  Instead, the callee should sync the decoder
 * by calling the sync() method after the entire frame 
 * has been decoded (modulo loss).
 *
 * This routine should not be called with more than
 * one frame present since there is no callback mechanism
 * for renderering frames (i.e., don't call this routine
 * with a buffer that has a picture header that's not
 * at the front).
 */
int P64Dumper::decode(const u_char* bp, int cc, int sbit, int ebit,
		      int mba, int gob, int mq, int mvdh, int mvdv)
{
	ps_ = (u_short*)bp;
	/*
	 * If cc is even, ignore 8 extra bits in last short.
	 */
	int odd = cc & 1;
	ebit += (odd ^ 1) << 3;
	pebit_ = ebit;
	cc -= odd;
	es_ = (u_short*)(bp + cc);

	/*
	 * If input buffer not aligned, prime bit-buffer
	 * with 8 bits; otherwise, prime it with a 16.
	 */
	if ((int)bp & 1) {
		bs_ = (u_short*)(bp + 1);
		bb_ = *bp;
		nbb_ = 8 - sbit;
	} else {
		bs_ = (u_short*)bp;
		HUFFRQ(bs_, bb_);
		nbb_ = 16 - sbit;
	}
	dbs_ = bs_;
	dnbb_ = nbb_;
	dbb_ = bb_;

	mba_ = mba;
	qt_ = &quant_[mq << 8];
	mvdh_ = mvdh;
	mvdv_ = mvdv;
	/*XXX don't rely on this*/
	if (gob != 0) {
		gob -= 1;
		if (fmt_ == IT_QCIF)
			gob >>= 1;
	}

	while (bs_ < es_ || (bs_ == es_ && nbb_ > ebit)) {
		mbst_ = &mb_state_[gob << 6];
		coord_ = &base_[gob << 6];

		int v = decode_mb();
		if (v == 0)
			continue;

		if (v != SYM_STARTCODE) {
			++bad_bits_;
			return (0);
		}
		gob = parse_gob_hdr(ebit);
		if (gob < 0) {
			/*XXX*/
			++bad_bits_;
			return (0);
		}
	}
	fflush(stdout);
	return (1);
}