mlpdec.c

ffmpeg移植到symbian的全部源代码

        return -1;
    }

    memset(&m->bypassed_lsbs[s->blockpos][0], 0,
           s->blocksize * sizeof(m->bypassed_lsbs[0]));

    for (i = 0; i < s->blocksize; i++) {
        if (read_huff_channels(m, gbp, substr, i) < 0)
            return -1;
    }

    for (ch = s->min_channel; ch <= s->max_channel; ch++) {
        filter_channel(m, substr, ch);
    }

    s->blockpos += s->blocksize;

    if (s->data_check_present) {
        if (get_bits_count(gbp) != expected_stream_pos)
            av_log(m->avctx, AV_LOG_ERROR, "block data length mismatch\n");
        skip_bits(gbp, 8);
    }

    return 0;
}

/** Data table used for TrueHD noise generation function. */

static const int8_t noise_table[256] = {
     30,  51,  22,  54,   3,   7,  -4,  38,  14,  55,  46,  81,  22,  58,  -3,   2,
     52,  31,  -7,  51,  15,  44,  74,  30,  85, -17,  10,  33,  18,  80,  28,  62,
     10,  32,  23,  69,  72,  26,  35,  17,  73,  60,   8,  56,   2,   6,  -2,  -5,
     51,   4,  11,  50,  66,  76,  21,  44,  33,  47,   1,  26,  64,  48,  57,  40,
     38,  16, -10, -28,  92,  22, -18,  29, -10,   5, -13,  49,  19,  24,  70,  34,
     61,  48,  30,  14,  -6,  25,  58,  33,  42,  60,  67,  17,  54,  17,  22,  30,
     67,  44,  -9,  50, -11,  43,  40,  32,  59,  82,  13,  49, -14,  55,  60,  36,
     48,  49,  31,  47,  15,  12,   4,  65,   1,  23,  29,  39,  45,  -2,  84,  69,
      0,  72,  37,  57,  27,  41, -15, -16,  35,  31,  14,  61,  24,   0,  27,  24,
     16,  41,  55,  34,  53,   9,  56,  12,  25,  29,  53,   5,  20, -20,  -8,  20,
     13,  28,  -3,  78,  38,  16,  11,  62,  46,  29,  21,  24,  46,  65,  43, -23,
     89,  18,  74,  21,  38, -12,  19,  12, -19,   8,  15,  33,   4,  57,   9,  -8,
     36,  35,  26,  28,   7,  83,  63,  79,  75,  11,   3,  87,  37,  47,  34,  40,
     39,  19,  20,  42,  27,  34,  39,  77,  13,  42,  59,  64,  45,  -1,  32,  37,
     45,  -5,  53,  -6,   7,  36,  50,  23,   6,  32,   9, -21,  18,  71,  27,  52,
    -25,  31,  35,  42,  -1,  68,  63,  52,  26,  43,  66,  37,  41,  25,  40,  70,
};

/** Noise generation functions.
 *  I'm not sure what these are for - they seem to be some kind of pseudorandom
 *  sequence generators, used to generate noise data which is used when the
 *  channels are rematrixed. I'm not sure if they provide a practical benefit
 *  to compression, or just obfuscate the decoder. Are they for some kind of
 *  dithering? */

/** Generate two channels of noise, used in the matrix when
 *  restart sync word == 0x31ea. */

static void generate_2_noise_channels(MLPDecodeContext *m, unsigned int substr)
{
    SubStream *s = &m->substream[substr];
    unsigned int i;
    uint32_t seed = s->noisegen_seed;
    unsigned int maxchan = s->max_matrix_channel;

    for (i = 0; i < s->blockpos; i++) {
        uint16_t seed_shr7 = seed >> 7;
        m->sample_buffer[i][maxchan+1] = ((int8_t)(seed >> 15)) << s->noise_shift;
        m->sample_buffer[i][maxchan+2] = ((int8_t) seed_shr7)   << s->noise_shift;

        seed = (seed << 16) ^ seed_shr7 ^ (seed_shr7 << 5);
    }

    s->noisegen_seed = seed;
}

/** Generate a block of noise, used when restart sync word == 0x31eb. */

static void fill_noise_buffer(MLPDecodeContext *m, unsigned int substr)
{
    SubStream *s = &m->substream[substr];
    unsigned int i;
    uint32_t seed = s->noisegen_seed;

    for (i = 0; i < m->access_unit_size_pow2; i++) {
        uint8_t seed_shr15 = seed >> 15;
        m->noise_buffer[i] = noise_table[seed_shr15];
        seed = (seed << 8) ^ seed_shr15 ^ (seed_shr15 << 5);
    }

    s->noisegen_seed = seed;
}


/** Apply the channel matrices in turn to reconstruct the original audio
 *  samples. */

static void rematrix_channels(MLPDecodeContext *m, unsigned int substr)
{
    SubStream *s = &m->substream[substr];
    unsigned int mat, src_ch, i;
    unsigned int maxchan;

    maxchan = s->max_matrix_channel;
    if (!s->noise_type) {
        generate_2_noise_channels(m, substr);
        maxchan += 2;
    } else {
        fill_noise_buffer(m, substr);
    }

    for (mat = 0; mat < s->num_primitive_matrices; mat++) {
        int matrix_noise_shift = s->matrix_noise_shift[mat];
        unsigned int dest_ch = s->matrix_out_ch[mat];
        int32_t mask = MSB_MASK(s->quant_step_size[dest_ch]);

        /* TODO: DSPContext? */

        for (i = 0; i < s->blockpos; i++) {
            int64_t accum = 0;
            for (src_ch = 0; src_ch <= maxchan; src_ch++) {
                accum += (int64_t)m->sample_buffer[i][src_ch]
                                  * s->matrix_coeff[mat][src_ch];
            }
            if (matrix_noise_shift) {
                uint32_t index = s->num_primitive_matrices - mat;
                index = (i * (index * 2 + 1) + index) & (m->access_unit_size_pow2 - 1);
                accum += m->noise_buffer[index] << (matrix_noise_shift + 7);
            }
            m->sample_buffer[i][dest_ch] = ((accum >> 14) & mask)
                                             + m->bypassed_lsbs[i][mat];
        }
    }
}

/** Write the audio data into the output buffer. */

static int output_data_internal(MLPDecodeContext *m, unsigned int substr,
                                uint8_t *data, unsigned int *data_size, int is32)
{
    SubStream *s = &m->substream[substr];
    unsigned int i, ch = 0;
    int32_t *data_32 = (int32_t*) data;
    int16_t *data_16 = (int16_t*) data;

    if (*data_size < (s->max_channel + 1) * s->blockpos * (is32 ? 4 : 2))
        return -1;

    for (i = 0; i < s->blockpos; i++) {
        for (ch = 0; ch <= s->max_channel; ch++) {
            int32_t sample = m->sample_buffer[i][ch] << s->output_shift[ch];
            s->lossless_check_data ^= (sample & 0xffffff) << ch;
            if (is32) *data_32++ = sample << 8;
            else      *data_16++ = sample >> 8;
        }
    }

    *data_size = i * ch * (is32 ? 4 : 2);

    return 0;
}

static int output_data(MLPDecodeContext *m, unsigned int substr,
                       uint8_t *data, unsigned int *data_size)
{
    if (m->avctx->sample_fmt == SAMPLE_FMT_S32)
        return output_data_internal(m, substr, data, data_size, 1);
    else
        return output_data_internal(m, substr, data, data_size, 0);
}


/** XOR together all the bytes of a buffer.
 *  Does this belong in dspcontext? */

static uint8_t calculate_parity(const uint8_t *buf, unsigned int buf_size)
{
    uint32_t scratch = 0;
    const uint8_t *buf_end = buf + buf_size;

    for (; buf < buf_end - 3; buf += 4)
        scratch ^= *((const uint32_t*)buf);

    scratch ^= scratch >> 16;
    scratch ^= scratch >> 8;

    for (; buf < buf_end; buf++)
        scratch ^= *buf;

    return scratch;
}

/** Read an access unit from the stream.
 *  Returns < 0 on error, 0 if not enough data is present in the input stream
 *  otherwise returns the number of bytes consumed. */

static int read_access_unit(AVCodecContext *avctx, void* data, int *data_size,
                            const uint8_t *buf, int buf_size)
{
    MLPDecodeContext *m = avctx->priv_data;
    GetBitContext gb;
    unsigned int length, substr;
    unsigned int substream_start;
    unsigned int header_size = 4;
    unsigned int substr_header_size = 0;
    uint8_t substream_parity_present[MAX_SUBSTREAMS];
    uint16_t substream_data_len[MAX_SUBSTREAMS];
    uint8_t parity_bits;

    if (buf_size < 4)
        return 0;

    length = (AV_RB16(buf) & 0xfff) * 2;

    if (length > buf_size)
        return -1;

    init_get_bits(&gb, (buf + 4), (length - 4) * 8);

    if (show_bits_long(&gb, 31) == (0xf8726fba >> 1)) {
        dprintf(m->avctx, "Found major sync.\n");
        if (read_major_sync(m, &gb) < 0)
            goto error;
        header_size += 28;
    }

    if (!m->params_valid) {
        av_log(m->avctx, AV_LOG_WARNING,
               "Stream parameters not seen; skipping frame.\n");
        *data_size = 0;
        return length;
    }

    substream_start = 0;

    for (substr = 0; substr < m->num_substreams; substr++) {
        int extraword_present, checkdata_present, end;

        extraword_present = get_bits1(&gb);
        skip_bits1(&gb);
        checkdata_present = get_bits1(&gb);
        skip_bits1(&gb);

        end = get_bits(&gb, 12) * 2;

        substr_header_size += 2;

        if (extraword_present) {
            skip_bits(&gb, 16);
            substr_header_size += 2;
        }

        if (end + header_size + substr_header_size > length) {
            av_log(m->avctx, AV_LOG_ERROR,
                   "Indicated length of substream %d data goes off end of "
                   "packet.\n", substr);
            end = length - header_size - substr_header_size;
        }

        if (end < substream_start) {
            av_log(avctx, AV_LOG_ERROR,
                   "Indicated end offset of substream %d data "
                   "is smaller than calculated start offset.\n",
                   substr);
            goto error;
        }

        if (substr > m->max_decoded_substream)
            continue;

        substream_parity_present[substr] = checkdata_present;
        substream_data_len[substr] = end - substream_start;
        substream_start = end;
    }

    parity_bits  = calculate_parity(buf, 4);
    parity_bits ^= calculate_parity(buf + header_size, substr_header_size);

    if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
        av_log(avctx, AV_LOG_ERROR, "Parity check failed.\n");
        goto error;
    }

    buf += header_size + substr_header_size;

    for (substr = 0; substr <= m->max_decoded_substream; substr++) {
        SubStream *s = &m->substream[substr];
        init_get_bits(&gb, buf, substream_data_len[substr] * 8);

        s->blockpos = 0;
        do {
            if (get_bits1(&gb)) {
                if (get_bits1(&gb)) {
                    /* A restart header should be present. */
                    if (read_restart_header(m, &gb, buf, substr) < 0)
                        goto next_substr;
                    s->restart_seen = 1;
                }

                if (!s->restart_seen) {
                    av_log(m->avctx, AV_LOG_ERROR,
                           "No restart header present in substream %d.\n",
                           substr);
                    goto next_substr;
                }

                if (read_decoding_params(m, &gb, substr) < 0)
                    goto next_substr;
            }

            if (!s->restart_seen) {
                av_log(m->avctx, AV_LOG_ERROR,
                       "No restart header present in substream %d.\n",
                       substr);
                goto next_substr;
            }

            if (read_block_data(m, &gb, substr) < 0)
                return -1;

        } while ((get_bits_count(&gb) < substream_data_len[substr] * 8)
                 && get_bits1(&gb) == 0);

        skip_bits(&gb, (-get_bits_count(&gb)) & 15);
        if (substream_data_len[substr] * 8 - get_bits_count(&gb) >= 32 &&
            (show_bits_long(&gb, 32) == 0xd234d234 ||
             show_bits_long(&gb, 20) == 0xd234e)) {
            skip_bits(&gb, 18);
            if (substr == m->max_decoded_substream)
                av_log(m->avctx, AV_LOG_INFO, "End of stream indicated.\n");

            if (get_bits1(&gb)) {
                int shorten_by = get_bits(&gb, 13);
                shorten_by = FFMIN(shorten_by, s->blockpos);
                s->blockpos -= shorten_by;
            } else
                skip_bits(&gb, 13);
        }
        if (substream_data_len[substr] * 8 - get_bits_count(&gb) >= 16 &&
            substream_parity_present[substr]) {
            uint8_t parity, checksum;

            parity = calculate_parity(buf, substream_data_len[substr] - 2);
            if ((parity ^ get_bits(&gb, 8)) != 0xa9)
                av_log(m->avctx, AV_LOG_ERROR,
                       "Substream %d parity check failed.\n", substr);

            checksum = mlp_checksum8(buf, substream_data_len[substr] - 2);
            if (checksum != get_bits(&gb, 8))
                av_log(m->avctx, AV_LOG_ERROR, "Substream %d checksum failed.\n",
                       substr);
        }
        if (substream_data_len[substr] * 8 != get_bits_count(&gb)) {
            av_log(m->avctx, AV_LOG_ERROR, "substream %d length mismatch\n",
                   substr);
            return -1;
        }

next_substr:
        buf += substream_data_len[substr];
    }

    rematrix_channels(m, m->max_decoded_substream);

#ifdef __CW32__
    if (output_data(m, m->max_decoded_substream, data, (unsigned int*)data_size) < 0)
#else
    if (output_data(m, m->max_decoded_substream, data, data_size) < 0)
#endif
        return -1;

    return length;

error:
    m->params_valid = 0;
    return -1;
}

AVCodec mlp_decoder = {
    "mlp",
    CODEC_TYPE_AUDIO,
    CODEC_ID_MLP,
    sizeof(MLPDecodeContext),
    mlp_decode_init,
    NULL,
    NULL,
    read_access_unit,
#ifdef __CW32__
    0,
    0,
    0,
    0,
    0,
    NULL_IF_CONFIG_SMALL("Meridian Lossless Packing"),
#else
    .long_name = NULL_IF_CONFIG_SMALL("Meridian Lossless Packing"),
#endif
};