vp3.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.10平台上编译为嵌入式图形界面操作系统。

        debug_dequantizers(" %4d,", s->inter_dequant[j]);
      }
      debug_dequantizers("\n");
    }
    debug_dequantizers("\n");
}

/*
 * This function is used to fetch runs of 1s or 0s from the bitstream for
 * use in determining which superblocks are fully and partially coded.
 *
 *  Codeword                RunLength
 *  0                       1
 *  10x                     2-3
 *  110x                    4-5
 *  1110xx                  6-9
 *  11110xxx                10-17
 *  111110xxxx              18-33
 *  111111xxxxxxxxxxxx      34-4129
 */
static int get_superblock_run_length(GetBitContext *gb)
{

    if (get_bits(gb, 1) == 0)
        return 1;

    else if (get_bits(gb, 1) == 0)
        return (2 + get_bits(gb, 1));

    else if (get_bits(gb, 1) == 0)
        return (4 + get_bits(gb, 1));

    else if (get_bits(gb, 1) == 0)
        return (6 + get_bits(gb, 2));

    else if (get_bits(gb, 1) == 0)
        return (10 + get_bits(gb, 3));

    else if (get_bits(gb, 1) == 0)
        return (18 + get_bits(gb, 4));

    else
        return (34 + get_bits(gb, 12));

}

/*
 * This function is used to fetch runs of 1s or 0s from the bitstream for
 * use in determining which particular fragments are coded.
 *
 * Codeword                RunLength
 * 0x                      1-2
 * 10x                     3-4
 * 110x                    5-6
 * 1110xx                  7-10
 * 11110xx                 11-14
 * 11111xxxx               15-30
 */
static int get_fragment_run_length(GetBitContext *gb)
{

    if (get_bits(gb, 1) == 0)
        return (1 + get_bits(gb, 1));

    else if (get_bits(gb, 1) == 0)
        return (3 + get_bits(gb, 1));

    else if (get_bits(gb, 1) == 0)
        return (5 + get_bits(gb, 1));

    else if (get_bits(gb, 1) == 0)
        return (7 + get_bits(gb, 2));

    else if (get_bits(gb, 1) == 0)
        return (11 + get_bits(gb, 2));

    else
        return (15 + get_bits(gb, 4));

}

/*
 * This function decodes a VLC from the bitstream and returns a number
 * that ranges from 0..7. The number indicates which of the 8 coding
 * modes to use.
 *
 *  VLC       Number
 *  0            0
 *  10           1
 *  110          2
 *  1110         3
 *  11110        4
 *  111110       5
 *  1111110      6
 *  1111111      7
 *
 */
static int get_mode_code(GetBitContext *gb)
{

    if (get_bits(gb, 1) == 0)
        return 0;

    else if (get_bits(gb, 1) == 0)
        return 1;

    else if (get_bits(gb, 1) == 0)
        return 2;

    else if (get_bits(gb, 1) == 0)
        return 3;

    else if (get_bits(gb, 1) == 0)
        return 4;

    else if (get_bits(gb, 1) == 0)
        return 5;

    else if (get_bits(gb, 1) == 0)
        return 6;

    else
        return 7;

}

/*
 * This function extracts a motion vector from the bitstream using a VLC
 * scheme. 3 bits are fetched from the bitstream and 1 of 8 actions is
 * taken depending on the value on those 3 bits:
 *
 *  0: return 0
 *  1: return 1
 *  2: return -1
 *  3: if (next bit is 1) return -2, else return 2
 *  4: if (next bit is 1) return -3, else return 3
 *  5: return 4 + (next 2 bits), next bit is sign
 *  6: return 8 + (next 3 bits), next bit is sign
 *  7: return 16 + (next 4 bits), next bit is sign
 */
static int get_motion_vector_vlc(GetBitContext *gb)
{
    int bits;

    bits = get_bits(gb, 3);

    switch(bits) {

    case 0:
        bits = 0;
        break;

    case 1:
        bits = 1;
        break;

    case 2:
        bits = -1;
        break;

    case 3:
        if (get_bits(gb, 1) == 0)
            bits = 2;
        else
            bits = -2;
        break;

    case 4:
        if (get_bits(gb, 1) == 0)
            bits = 3;
        else
            bits = -3;
        break;

    case 5:
        bits = 4 + get_bits(gb, 2);
        if (get_bits(gb, 1) == 1)
            bits = -bits;
        break;

    case 6:
        bits = 8 + get_bits(gb, 3);
        if (get_bits(gb, 1) == 1)
            bits = -bits;
        break;

    case 7:
        bits = 16 + get_bits(gb, 4);
        if (get_bits(gb, 1) == 1)
            bits = -bits;
        break;

    }

    return bits;
}

/*
 * This function fetches a 5-bit number from the stream followed by
 * a sign and calls it a motion vector.
 */
static int get_motion_vector_fixed(GetBitContext *gb)
{

    int bits;

    bits = get_bits(gb, 5);

    if (get_bits(gb, 1) == 1)
        bits = -bits;

    return bits;
}

/*
 * This function unpacks all of the superblock/macroblock/fragment coding 
 * information from the bitstream.
 */
static int unpack_superblocks(Vp3DecodeContext *s, GetBitContext *gb)
{
    int bit = 0;
    int current_superblock = 0;
    int current_run = 0;
    int decode_fully_flags = 0;
    int decode_partial_blocks = 0;
    int first_c_fragment_seen;

    int i, j;
    int current_fragment;

    debug_vp3("  vp3: unpacking superblock coding\n");

    if (s->keyframe) {

        debug_vp3("    keyframe-- all superblocks are fully coded\n");
        memset(s->superblock_coding, SB_FULLY_CODED, s->superblock_count);

    } else {

        /* unpack the list of partially-coded superblocks */
        bit = get_bits(gb, 1);
        /* toggle the bit because as soon as the first run length is 
         * fetched the bit will be toggled again */
        bit ^= 1;
        while (current_superblock < s->superblock_count) {
            if (current_run == 0) {
                bit ^= 1;
                current_run = get_superblock_run_length(gb);
                debug_block_coding("      setting superblocks %d..%d to %s\n",
                    current_superblock,
                    current_superblock + current_run - 1,
                    (bit) ? "partially coded" : "not coded");

                /* if any of the superblocks are not partially coded, flag
                 * a boolean to decode the list of fully-coded superblocks */
                if (bit == 0) {
                    decode_fully_flags = 1;
                } else {

                    /* make a note of the fact that there are partially coded
                     * superblocks */
                    decode_partial_blocks = 1;
                }
            }
            s->superblock_coding[current_superblock++] = 
                (bit) ? SB_PARTIALLY_CODED : SB_NOT_CODED;
            current_run--;
        }

        /* unpack the list of fully coded superblocks if any of the blocks were
         * not marked as partially coded in the previous step */
        if (decode_fully_flags) {

            current_superblock = 0;
            current_run = 0;
            bit = get_bits(gb, 1);
            /* toggle the bit because as soon as the first run length is 
             * fetched the bit will be toggled again */
            bit ^= 1;
            while (current_superblock < s->superblock_count) {

                /* skip any superblocks already marked as partially coded */
                if (s->superblock_coding[current_superblock] == SB_NOT_CODED) {

                    if (current_run == 0) {
                        bit ^= 1;
                        current_run = get_superblock_run_length(gb);
                    }

                    debug_block_coding("      setting superblock %d to %s\n",
                        current_superblock,
                        (bit) ? "fully coded" : "not coded");
                    s->superblock_coding[current_superblock] = 
                        (bit) ? SB_FULLY_CODED : SB_NOT_CODED;
                    current_run--;
                }
                current_superblock++;
            }
        }

        /* if there were partial blocks, initialize bitstream for
         * unpacking fragment codings */
        if (decode_partial_blocks) {

            current_run = 0;
            bit = get_bits(gb, 1);
            /* toggle the bit because as soon as the first run length is 
             * fetched the bit will be toggled again */
            bit ^= 1;
        }
    }

    /* figure out which fragments are coded; iterate through each
     * superblock (all planes) */
    s->coded_fragment_list_index = 0;
    s->first_coded_y_fragment = s->first_coded_c_fragment = 0;
    s->last_coded_y_fragment = s->last_coded_c_fragment = -1;
    first_c_fragment_seen = 0;
    memset(s->macroblock_coding, MODE_COPY, s->macroblock_count);
    for (i = 0; i < s->superblock_count; i++) {

        /* iterate through all 16 fragments in a superblock */
        for (j = 0; j < 16; j++) {

            /* if the fragment is in bounds, check its coding status */
            current_fragment = s->superblock_fragments[i * 16 + j];
            if (current_fragment >= s->fragment_count) {
                av_log(s->avctx, AV_LOG_ERROR, "  vp3:unpack_superblocks(): bad fragment number (%d >= %d)\n",
                    current_fragment, s->fragment_count);
                return 1;
            }
            if (current_fragment != -1) {
                if (s->superblock_coding[i] == SB_NOT_CODED) {

                    /* copy all the fragments from the prior frame */
                    s->all_fragments[current_fragment].coding_method = 
                        MODE_COPY;

                } else if (s->superblock_coding[i] == SB_PARTIALLY_CODED) {

                    /* fragment may or may not be coded; this is the case
                     * that cares about the fragment coding runs */
                    if (current_run == 0) {
                        bit ^= 1;
                        current_run = get_fragment_run_length(gb);
                    }

                    if (bit) {
                        /* default mode; actual mode will be decoded in 
                         * the next phase */
                        s->all_fragments[current_fragment].coding_method = 
                            MODE_INTER_NO_MV;
                        s->coded_fragment_list[s->coded_fragment_list_index] = 
                            current_fragment;
                        if ((current_fragment >= s->u_fragment_start) &&
                            (s->last_coded_y_fragment == -1) &&
                            (!first_c_fragment_seen)) {
                            s->first_coded_c_fragment = s->coded_fragment_list_index;
                            s->last_coded_y_fragment = s->first_coded_c_fragment - 1;
                            first_c_fragment_seen = 1;
                        }
                        s->coded_fragment_list_index++;
                        s->macroblock_coding[s->all_fragments[current_fragment].macroblock] = MODE_INTER_NO_MV;
                        debug_block_coding("      superblock %d is partially coded, fragment %d is coded\n",
                            i, current_fragment);
                    } else {
                        /* not coded; copy this fragment from the prior frame */
                        s->all_fragments[current_fragment].coding_method =
                            MODE_COPY;
                        debug_block_coding("      superblock %d is partially coded, fragment %d is not coded\n",
                            i, current_fragment);
                    }

                    current_run--;

                } else {

                    /* fragments are fully coded in this superblock; actual
                     * coding will be determined in next step */
                    s->all_fragments[current_fragment].coding_method = 
                        MODE_INTER_NO_MV;
                    s->coded_fragment_list[s->coded_fragment_list_index] = 
                        current_fragment;
                    if ((current_fragment >= s->u_fragment_start) &&
                        (s->last_coded_y_fragment == -1) &&
                        (!first_c_fragment_seen)) {
                        s->first_coded_c_fragment = s->coded_fragment_list_index;
                        s->last_coded_y_fragment = s->first_coded_c_fragment - 1;
                        first_c_fragment_seen = 1;
                    }
                    s->coded_fragment_list_index++;
                    s->macroblock_coding[s->all_fragments[current_fragment].macroblock] = MODE_INTER_NO_MV;
                    debug_block_coding("      superblock %d is fully coded, fragment %d is coded\n",
                        i, current_fragment);
                }
            }
        }
    }

    if (!first_c_fragment_seen)
        /* only Y fragments coded in this frame */
        s->last_coded_y_fragment = s->coded_fragment_list_index - 1;
    else 
        /* end the list of coded C fragments */
        s->last_coded_c_fragment = s->coded_fragment_list_index - 1;

    debug_block_coding("    %d total coded fragments, y: %d -> %d, c: %d -> %d\n",
        s->coded_fragment_list_index,