vp3.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

 * This function sets up all of the various blocks mappings:
 * superblocks <-> fragments, macroblocks <-> fragments,
 * superblocks <-> macroblocks
 *
 * Returns 0 is successful; returns 1 if *anything* went wrong.
 */
static int init_block_mapping(Vp3DecodeContext *s)
{
    int i, j;
    signed int hilbert_walk_mb[4];

    int current_fragment = 0;
    int current_width = 0;
    int current_height = 0;
    int right_edge = 0;
    int bottom_edge = 0;
    int superblock_row_inc = 0;
    int *hilbert = NULL;
    int mapping_index = 0;

    int current_macroblock;
    int c_fragment;

    signed char travel_width[16] = {
         1,  1,  0, -1,
         0,  0,  1,  0,
         1,  0,  1,  0,
         0, -1,  0,  1
    };

    signed char travel_height[16] = {
         0,  0,  1,  0,
         1,  1,  0, -1,
         0,  1,  0, -1,
        -1,  0, -1,  0
    };

    signed char travel_width_mb[4] = {
         1,  0,  1,  0
    };

    signed char travel_height_mb[4] = {
         0,  1,  0, -1
    };

    debug_vp3("  vp3: initialize block mapping tables\n");

    hilbert_walk_mb[0] = 1;
    hilbert_walk_mb[1] = s->macroblock_width;
    hilbert_walk_mb[2] = 1;
    hilbert_walk_mb[3] = -s->macroblock_width;

    /* iterate through each superblock (all planes) and map the fragments */
    for (i = 0; i < s->superblock_count; i++) {
        debug_init("    superblock %d (u starts @ %d, v starts @ %d)\n",
            i, s->u_superblock_start, s->v_superblock_start);

        /* time to re-assign the limits? */
        if (i == 0) {

            /* start of Y superblocks */
            right_edge = s->fragment_width;
            bottom_edge = s->fragment_height;
            current_width = -1;
            current_height = 0;
            superblock_row_inc = 3 * s->fragment_width -
                (s->y_superblock_width * 4 - s->fragment_width);

            /* the first operation for this variable is to advance by 1 */
            current_fragment = -1;

        } else if (i == s->u_superblock_start) {

            /* start of U superblocks */
            right_edge = s->fragment_width / 2;
            bottom_edge = s->fragment_height / 2;
            current_width = -1;
            current_height = 0;
            superblock_row_inc = 3 * (s->fragment_width / 2) -
                (s->c_superblock_width * 4 - s->fragment_width / 2);

            /* the first operation for this variable is to advance by 1 */
            current_fragment = s->fragment_start[1] - 1;

        } else if (i == s->v_superblock_start) {

            /* start of V superblocks */
            right_edge = s->fragment_width / 2;
            bottom_edge = s->fragment_height / 2;
            current_width = -1;
            current_height = 0;
            superblock_row_inc = 3 * (s->fragment_width / 2) -
                (s->c_superblock_width * 4 - s->fragment_width / 2);

            /* the first operation for this variable is to advance by 1 */
            current_fragment = s->fragment_start[2] - 1;

        }

        if (current_width >= right_edge - 1) {
            /* reset width and move to next superblock row */
            current_width = -1;
            current_height += 4;

            /* fragment is now at the start of a new superblock row */
            current_fragment += superblock_row_inc;
        }

        /* iterate through all 16 fragments in a superblock */
        for (j = 0; j < 16; j++) {
            current_fragment += travel_width[j] + right_edge * travel_height[j];
            current_width += travel_width[j];
            current_height += travel_height[j];

            /* check if the fragment is in bounds */
            if ((current_width < right_edge) &&
                (current_height < bottom_edge)) {
                s->superblock_fragments[mapping_index] = current_fragment;
                debug_init("    mapping fragment %d to superblock %d, position %d (%d/%d x %d/%d)\n",
                    s->superblock_fragments[mapping_index], i, j,
                    current_width, right_edge, current_height, bottom_edge);
            } else {
                s->superblock_fragments[mapping_index] = -1;
                debug_init("    superblock %d, position %d has no fragment (%d/%d x %d/%d)\n",
                    i, j,
                    current_width, right_edge, current_height, bottom_edge);
            }

            mapping_index++;
        }
    }

    /* initialize the superblock <-> macroblock mapping; iterate through
     * all of the Y plane superblocks to build this mapping */
    right_edge = s->macroblock_width;
    bottom_edge = s->macroblock_height;
    current_width = -1;
    current_height = 0;
    superblock_row_inc = s->macroblock_width -
        (s->y_superblock_width * 2 - s->macroblock_width);;
    hilbert = hilbert_walk_mb;
    mapping_index = 0;
    current_macroblock = -1;
    for (i = 0; i < s->u_superblock_start; i++) {

        if (current_width >= right_edge - 1) {
            /* reset width and move to next superblock row */
            current_width = -1;
            current_height += 2;

            /* macroblock is now at the start of a new superblock row */
            current_macroblock += superblock_row_inc;
        }

        /* iterate through each potential macroblock in the superblock */
        for (j = 0; j < 4; j++) {
            current_macroblock += hilbert_walk_mb[j];
            current_width += travel_width_mb[j];
            current_height += travel_height_mb[j];

            /* check if the macroblock is in bounds */
            if ((current_width < right_edge) &&
                (current_height < bottom_edge)) {
                s->superblock_macroblocks[mapping_index] = current_macroblock;
                debug_init("    mapping macroblock %d to superblock %d, position %d (%d/%d x %d/%d)\n",
                    s->superblock_macroblocks[mapping_index], i, j,
                    current_width, right_edge, current_height, bottom_edge);
            } else {
                s->superblock_macroblocks[mapping_index] = -1;
                debug_init("    superblock %d, position %d has no macroblock (%d/%d x %d/%d)\n",
                    i, j,
                    current_width, right_edge, current_height, bottom_edge);
            }

            mapping_index++;
        }
    }

    /* initialize the macroblock <-> fragment mapping */
    current_fragment = 0;
    current_macroblock = 0;
    mapping_index = 0;
    for (i = 0; i < s->fragment_height; i += 2) {

        for (j = 0; j < s->fragment_width; j += 2) {

            debug_init("    macroblock %d contains fragments: ", current_macroblock);
            s->all_fragments[current_fragment].macroblock = current_macroblock;
            s->macroblock_fragments[mapping_index++] = current_fragment;
            debug_init("%d ", current_fragment);

            if (j + 1 < s->fragment_width) {
                s->all_fragments[current_fragment + 1].macroblock = current_macroblock;
                s->macroblock_fragments[mapping_index++] = current_fragment + 1;
                debug_init("%d ", current_fragment + 1);
            } else
                s->macroblock_fragments[mapping_index++] = -1;

            if (i + 1 < s->fragment_height) {
                s->all_fragments[current_fragment + s->fragment_width].macroblock =
                    current_macroblock;
                s->macroblock_fragments[mapping_index++] =
                    current_fragment + s->fragment_width;
                debug_init("%d ", current_fragment + s->fragment_width);
            } else
                s->macroblock_fragments[mapping_index++] = -1;

            if ((j + 1 < s->fragment_width) && (i + 1 < s->fragment_height)) {
                s->all_fragments[current_fragment + s->fragment_width + 1].macroblock =
                    current_macroblock;
                s->macroblock_fragments[mapping_index++] =
                    current_fragment + s->fragment_width + 1;
                debug_init("%d ", current_fragment + s->fragment_width + 1);
            } else
                s->macroblock_fragments[mapping_index++] = -1;

            /* C planes */
            c_fragment = s->fragment_start[1] +
                (i * s->fragment_width / 4) + (j / 2);
            s->all_fragments[c_fragment].macroblock = s->macroblock_count;
            s->macroblock_fragments[mapping_index++] = c_fragment;
            debug_init("%d ", c_fragment);

            c_fragment = s->fragment_start[2] +
                (i * s->fragment_width / 4) + (j / 2);
            s->all_fragments[c_fragment].macroblock = s->macroblock_count;
            s->macroblock_fragments[mapping_index++] = c_fragment;
            debug_init("%d ", c_fragment);

            debug_init("\n");

            if (j + 2 <= s->fragment_width)
                current_fragment += 2;
            else
                current_fragment++;
            current_macroblock++;
        }

        current_fragment += s->fragment_width;
    }

    return 0;  /* successful path out */
}

/*
 * This function wipes out all of the fragment data.
 */
static void init_frame(Vp3DecodeContext *s, GetBitContext *gb)
{
    int i;

    /* zero out all of the fragment information */
    s->coded_fragment_list_index = 0;
    for (i = 0; i < s->fragment_count; i++) {
        s->all_fragments[i].coeff_count = 0;
        s->all_fragments[i].motion_x = 127;
        s->all_fragments[i].motion_y = 127;
        s->all_fragments[i].next_coeff= NULL;
        s->coeffs[i].index=
        s->coeffs[i].coeff=0;
        s->coeffs[i].next= NULL;
    }
}

/*
 * This function sets up the dequantization tables used for a particular
 * frame.
 */
static void init_dequantizer(Vp3DecodeContext *s)
{
    int ac_scale_factor = s->coded_ac_scale_factor[s->quality_index];
    int dc_scale_factor = s->coded_dc_scale_factor[s->quality_index];
    int i, plane, inter, qri, bmi, bmj, qistart;

    debug_vp3("  vp3: initializing dequantization tables\n");

    for(inter=0; inter<2; inter++){
        for(plane=0; plane<3; plane++){
            int sum=0;
            for(qri=0; qri<s->qr_count[inter][plane]; qri++){
                sum+= s->qr_size[inter][plane][qri];
                if(s->quality_index <= sum)
                    break;
            }
            qistart= sum - s->qr_size[inter][plane][qri];
            bmi= s->qr_base[inter][plane][qri  ];
            bmj= s->qr_base[inter][plane][qri+1];
            for(i=0; i<64; i++){
                int coeff= (  2*(sum    -s->quality_index)*s->base_matrix[bmi][i]
                            - 2*(qistart-s->quality_index)*s->base_matrix[bmj][i]
                            + s->qr_size[inter][plane][qri])
                           / (2*s->qr_size[inter][plane][qri]);

                int qmin= 8<<(inter + !i);
                int qscale= i ? ac_scale_factor : dc_scale_factor;

                s->qmat[inter][plane][i]= av_clip((qscale * coeff)/100 * 4, qmin, 4096);
            }
        }
    }

    memset(s->qscale_table, (FFMAX(s->qmat[0][0][1], s->qmat[0][1][1])+8)/16, 512); //FIXME finetune
}

/*
 * This function initializes the loop filter boundary limits if the frame's
 * quality index is different from the previous frame's.
 */
static void init_loop_filter(Vp3DecodeContext *s)
{
    int *bounding_values= s->bounding_values_array+127;
    int filter_limit;
    int x;

    filter_limit = s->filter_limit_values[s->quality_index];

    /* set up the bounding values */
    memset(s->bounding_values_array, 0, 256 * sizeof(int));
    for (x = 0; x < filter_limit; x++) {
        bounding_values[-x - filter_limit] = -filter_limit + x;
        bounding_values[-x] = -x;
        bounding_values[x] = x;
        bounding_values[x + filter_limit] = filter_limit - x;
    }
}

/*
 * 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;