unpack.c

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// This monster actually unpacks the WavPack bitstream(s) into the specified
// buffer as 32-bit integers or floats (depending on orignal data). Lossy
// samples will be clipped to their original limits (i.e. 8-bit samples are
// clipped to -128/+127) but are still returned in longs. It is up to the
// caller to potentially reformat this for the final output including any
// multichannel distribution, block alignment or endian compensation. The
// function unpack_init() must have been called and the entire WavPack block
// must still be visible (although wps->blockbuff will not be accessed again).
// For maximum clarity, the function is broken up into segments that handle
// various modes. This makes for a few extra infrequent flag checks, but
// makes the code easier to follow because the nesting does not become so
// deep. For maximum efficiency, the conversion is isolated to tight loops
// that handle an entire buffer. The function returns the total number of
// samples unpacked, which can be less than the number requested if an error
// occurs or the end of the block is reached.

static void fixup_samples (WavpackStream *wps, long *buffer, ulong sample_count);

long unpack_samples (WavpackContext *wpc, long *buffer, ulong sample_count)
{
    WavpackStream *wps = &wpc->stream;
    ulong flags = wps->wphdr.flags, crc = wps->crc, i;
    long mute_limit = (1L << ((flags & MAG_MASK) >> MAG_LSB)) + 2;
    struct decorr_pass *dpp;
    long read_word, *bptr;
    int tcount, m = 0;

    if (wps->sample_index + sample_count > wps->wphdr.block_index + wps->wphdr.block_samples)
	sample_count = wps->wphdr.block_index + wps->wphdr.block_samples - wps->sample_index;

    if (wps->mute_error) {
	memset (buffer, 0, sample_count * (flags & MONO_FLAG ? 4 : 8));
	wps->sample_index += sample_count;
	return sample_count;
    }

    if (flags & HYBRID_FLAG)
	mute_limit *= 2;

    ///////////////////// handle version 4 mono data /////////////////////////

    if (flags & MONO_FLAG)
	for (bptr = buffer, i = 0; i < sample_count; ++i) {
	    if ((read_word = get_word (wps, 0)) == WORD_EOF)
		break;

	    for (tcount = wps->num_terms, dpp = wps->decorr_passes; tcount--; dpp++) {
		long sam, temp;
		int k;

		if (dpp->term > MAX_TERM) {
		    if (dpp->term & 1)
			sam = 2 * dpp->samples_A [0] - dpp->samples_A [1];
		    else
			sam = (3 * dpp->samples_A [0] - dpp->samples_A [1]) >> 1;

		    dpp->samples_A [1] = dpp->samples_A [0];
		    k = 0;
		}
		else {
		    sam = dpp->samples_A [m];
		    k = (m + dpp->term) & (MAX_TERM - 1);
		}

		temp = apply_weight (dpp->weight_A, sam) + read_word;
		update_weight (dpp->weight_A, dpp->delta, sam, read_word);
		dpp->samples_A [k] = read_word = temp;
	    }

	    if (labs (read_word) > mute_limit)
		break;

	    m = (m + 1) & (MAX_TERM - 1);
	    crc = crc * 3 + read_word;
	    *bptr++ = read_word;
	}

    //////////////////// handle version 4 stereo data ////////////////////////

    else
	for (bptr = buffer, i = 0; i < sample_count; ++i) {
	    long left, right, left2, right2;

	    if ((left = get_word (wps, 0)) == WORD_EOF ||
		(right = get_word (wps, 1)) == WORD_EOF)
		    break;

	    for (tcount = wps->num_terms, dpp = wps->decorr_passes; tcount--; dpp++)
		if (dpp->term > 0) {
		    long sam_A, sam_B;
		    int k;

		    if (dpp->term > MAX_TERM) {
			if (dpp->term & 1) {
			    sam_A = 2 * dpp->samples_A [0] - dpp->samples_A [1];
			    sam_B = 2 * dpp->samples_B [0] - dpp->samples_B [1];
			}
			else {
			    sam_A = (3 * dpp->samples_A [0] - dpp->samples_A [1]) >> 1;
			    sam_B = (3 * dpp->samples_B [0] - dpp->samples_B [1]) >> 1;
			}

			dpp->samples_A [1] = dpp->samples_A [0];
			dpp->samples_B [1] = dpp->samples_B [0];
			k = 0;
		    }
		    else {
			sam_A = dpp->samples_A [m];
			sam_B = dpp->samples_B [m];
			k = (m + dpp->term) & (MAX_TERM - 1);
		    }

		    left2 = apply_weight (dpp->weight_A, sam_A) + left;
		    right2 = apply_weight (dpp->weight_B, sam_B) + right;

		    update_weight (dpp->weight_A, dpp->delta, sam_A, left);
		    update_weight (dpp->weight_B, dpp->delta, sam_B, right);

		    dpp->samples_A [k] = left = left2;
		    dpp->samples_B [k] = right = right2;
		}
		else if (dpp->term == -1) {
		    left2 = left + apply_weight (dpp->weight_A, dpp->samples_A [0]);
		    update_weight_clip (dpp->weight_A, dpp->delta, dpp->samples_A [0], left);
		    left = left2;
		    right2 = right + apply_weight (dpp->weight_B, left2);
		    update_weight_clip (dpp->weight_B, dpp->delta, left2, right);
		    dpp->samples_A [0] = right = right2;
		}
		else {
		    right2 = right + apply_weight (dpp->weight_B, dpp->samples_B [0]);
		    update_weight_clip (dpp->weight_B, dpp->delta, dpp->samples_B [0], right);
		    right = right2;

		    if (dpp->term == -3) {
			right2 = dpp->samples_A [0];
			dpp->samples_A [0] = right;
		    }

		    left2 = left + apply_weight (dpp->weight_A, right2);
		    update_weight_clip (dpp->weight_A, dpp->delta, right2, left);
		    dpp->samples_B [0] = left = left2;
		}

	    m = (m + 1) & (MAX_TERM - 1);

	    if (flags & JOINT_STEREO)
		left += (right -= (left >> 1));

	    if (labs (left) > mute_limit || labs (right) > mute_limit)
		break;

	    crc = (crc * 3 + left) * 3 + right;
	    *bptr++ = left;
	    *bptr++ = right;
	}

    if (i != sample_count) {
	memset (buffer, 0, sample_count * (flags & MONO_FLAG ? 4 : 8));
	wps->mute_error = TRUE;
	i = sample_count;
    }

    while (m--)
	for (tcount = wps->num_terms, dpp = wps->decorr_passes; tcount--; dpp++)
	    if (dpp->term > 0 && dpp->term <= MAX_TERM) {
		long temp = dpp->samples_A [0];
		memcpy (dpp->samples_A, dpp->samples_A + 1, sizeof (dpp->samples_A) - sizeof (dpp->samples_A [0]));
		dpp->samples_A [MAX_TERM - 1] = temp;
		temp = dpp->samples_B [0];
		memcpy (dpp->samples_B, dpp->samples_B + 1, sizeof (dpp->samples_B) - sizeof (dpp->samples_B [0]));
		dpp->samples_B [MAX_TERM - 1] = temp;
	    }

    fixup_samples (wps, buffer, i);

    if (flags & FLOAT_DATA)
	float_normalize (buffer, (flags & MONO_FLAG) ? i : i * 2,
	    127 - wps->float_norm_exp + wpc->norm_offset);

    wps->sample_index += i;
    wps->crc = crc;

    return i;
}

// This is a helper function for unpack_samples() that applies several final
// operations. First, if the data is 32-bit float data, then that conversion
// is done in the float.c module (whether lossy or lossless) and we return.
// Otherwise, if the extended integer data applies, then that operation is
// executed first. If the unpacked data is lossy (and not corrected) then
// it is clipped and shifted in a single operation. Otherwise, if it's
// lossless then the last step is to apply the final shift (if any).

static void fixup_samples (WavpackStream *wps, long *buffer, ulong sample_count)
{
    ulong flags = wps->wphdr.flags;
    int shift = (flags & SHIFT_MASK) >> SHIFT_LSB;

    if (flags & FLOAT_DATA) {
	float_values (wps, buffer, (flags & MONO_FLAG) ? sample_count : sample_count * 2);
	return;
    }

    if (flags & INT32_DATA) {
	ulong count = (flags & MONO_FLAG) ? sample_count : sample_count * 2;
	int sent_bits = wps->int32_sent_bits, zeros = wps->int32_zeros;
	int ones = wps->int32_ones, dups = wps->int32_dups;
//	ulong mask = (1 << sent_bits) - 1;
	long *dptr = buffer;

	if (!(flags & HYBRID_FLAG) && !sent_bits && (zeros + ones + dups))
	    while (count--) {
		if (zeros)
		    *dptr <<= zeros;
		else if (ones)
		    *dptr = ((*dptr + 1) << ones) - 1;
		else if (dups)
		    *dptr = ((*dptr + (*dptr & 1)) << dups) - (*dptr & 1);

		dptr++;
	    }
	else
	    shift += zeros + sent_bits + ones + dups;
    }

    if (flags & HYBRID_FLAG) {
	long min_value, max_value, min_shifted, max_shifted;

	switch (flags & BYTES_STORED) {
	    case 0:
		min_shifted = (min_value = -128 >> shift) << shift;
		max_shifted = (max_value = 127 >> shift) << shift;
		break;

	    case 1:
		min_shifted = (min_value = -32768 >> shift) << shift;
		max_shifted = (max_value = 32767 >> shift) << shift;
		break;

	    case 2:
		min_shifted = (min_value = -8388608 >> shift) << shift;
		max_shifted = (max_value = 8388607 >> shift) << shift;
		break;

	    case 3:
		min_shifted = (min_value = -(long)2147483648 >> shift) << shift;
		max_shifted = (max_value = (long) 2147483647 >> shift) << shift;
		break;
	}

	if (!(flags & MONO_FLAG))
	    sample_count *= 2;

	while (sample_count--) {
	    if (*buffer < min_value)
		*buffer++ = min_shifted;
	    else if (*buffer > max_value)
		*buffer++ = max_shifted;
	    else
		*buffer++ <<= shift;
	}
    }
    else if (shift) {
	if (!(flags & MONO_FLAG))
	    sample_count *= 2;

	while (sample_count--)
	    *buffer++ <<= shift;
    }
}

// This function checks the crc value(s) for an unpacked block, returning the
// number of actual crc errors detected for the block. The block must be
// completely unpacked before this test is valid. For losslessly unpacked
// blocks of float or extended integer data the extended crc is also checked.
// Note that WavPack's crc is not a CCITT approved polynomial algorithm, but
// is a much simpler method that is virtually as robust for real world data.

int check_crc_error (WavpackContext *wpc)
{
    WavpackStream *wps = &wpc->stream;
    int result = 0;

    if (wps->crc != wps->wphdr.crc)
	++result;

    return result;
}