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

                case MODE_INTER_PLUS_MV:
                case MODE_GOLDEN_MV:
                    /* all 6 fragments use the same motion vector */
                    if (coding_mode == 0) {
                        motion_x[0] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                        motion_y[0] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                    } else {
                        motion_x[0] = fixed_motion_vector_table[get_bits(gb, 6)];
                        motion_y[0] = fixed_motion_vector_table[get_bits(gb, 6)];
                    }

                    for (k = 1; k < 6; k++) {
                        motion_x[k] = motion_x[0];
                        motion_y[k] = motion_y[0];
                    }

                    /* vector maintenance, only on MODE_INTER_PLUS_MV */
                    if (s->macroblock_coding[current_macroblock] ==
                        MODE_INTER_PLUS_MV) {
                        prior_last_motion_x = last_motion_x;
                        prior_last_motion_y = last_motion_y;
                        last_motion_x = motion_x[0];
                        last_motion_y = motion_y[0];
                    }
                    break;

                case MODE_INTER_FOURMV:
                    /* fetch 4 vectors from the bitstream, one for each
                     * Y fragment, then average for the C fragment vectors */
                    motion_x[4] = motion_y[4] = 0;
                    for (k = 0; k < 4; k++) {
                        if (coding_mode == 0) {
                            motion_x[k] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                            motion_y[k] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                        } else {
                            motion_x[k] = fixed_motion_vector_table[get_bits(gb, 6)];
                            motion_y[k] = fixed_motion_vector_table[get_bits(gb, 6)];
                        }
                        motion_x[4] += motion_x[k];
                        motion_y[4] += motion_y[k];
                    }

                    motion_x[5]=
                    motion_x[4]= RSHIFT(motion_x[4], 2);
                    motion_y[5]=
                    motion_y[4]= RSHIFT(motion_y[4], 2);

                    /* vector maintenance; vector[3] is treated as the
                     * last vector in this case */
                    prior_last_motion_x = last_motion_x;
                    prior_last_motion_y = last_motion_y;
                    last_motion_x = motion_x[3];
                    last_motion_y = motion_y[3];
                    break;

                case MODE_INTER_LAST_MV:
                    /* all 6 fragments use the last motion vector */
                    motion_x[0] = last_motion_x;
                    motion_y[0] = last_motion_y;
                    for (k = 1; k < 6; k++) {
                        motion_x[k] = motion_x[0];
                        motion_y[k] = motion_y[0];
                    }

                    /* no vector maintenance (last vector remains the
                     * last vector) */
                    break;

                case MODE_INTER_PRIOR_LAST:
                    /* all 6 fragments use the motion vector prior to the
                     * last motion vector */
                    motion_x[0] = prior_last_motion_x;
                    motion_y[0] = prior_last_motion_y;
                    for (k = 1; k < 6; k++) {
                        motion_x[k] = motion_x[0];
                        motion_y[k] = motion_y[0];
                    }

                    /* vector maintenance */
                    prior_last_motion_x = last_motion_x;
                    prior_last_motion_y = last_motion_y;
                    last_motion_x = motion_x[0];
                    last_motion_y = motion_y[0];
                    break;

                default:
                    /* covers intra, inter without MV, golden without MV */
                    memset(motion_x, 0, 6 * sizeof(int));
                    memset(motion_y, 0, 6 * sizeof(int));

                    /* no vector maintenance */
                    break;
                }

                /* assign the motion vectors to the correct fragments */
                debug_vectors("    vectors for macroblock starting @ fragment %d (coding method %d):\n",
                    current_fragment,
                    s->macroblock_coding[current_macroblock]);
                for (k = 0; k < 6; k++) {
                    current_fragment =
                        s->macroblock_fragments[current_macroblock * 6 + k];
                    if (current_fragment == -1)
                        continue;
                    if (current_fragment >= s->fragment_count) {
                        av_log(s->avctx, AV_LOG_ERROR, "  vp3:unpack_vectors(): bad fragment number (%d >= %d)\n",
                            current_fragment, s->fragment_count);
                        return 1;
                    }
                    s->all_fragments[current_fragment].motion_x = motion_x[k];
                    s->all_fragments[current_fragment].motion_y = motion_y[k];
                    debug_vectors("    vector %d: fragment %d = (%d, %d)\n",
                        k, current_fragment, motion_x[k], motion_y[k]);
                }
            }
        }
    }

    return 0;
}

/*
 * This function is called by unpack_dct_coeffs() to extract the VLCs from
 * the bitstream. The VLCs encode tokens which are used to unpack DCT
 * data. This function unpacks all the VLCs for either the Y plane or both
 * C planes, and is called for DC coefficients or different AC coefficient
 * levels (since different coefficient types require different VLC tables.
 *
 * This function returns a residual eob run. E.g, if a particular token gave
 * instructions to EOB the next 5 fragments and there were only 2 fragments
 * left in the current fragment range, 3 would be returned so that it could
 * be passed into the next call to this same function.
 */
static int unpack_vlcs(Vp3DecodeContext *s, GetBitContext *gb,
                        VLC *table, int coeff_index,
                        int first_fragment, int last_fragment,
                        int eob_run)
{
    int i;
    int token;
    int zero_run = 0;
    DCTELEM coeff = 0;
    Vp3Fragment *fragment;
    uint8_t *perm= s->scantable.permutated;
    int bits_to_get;

    if ((first_fragment >= s->fragment_count) ||
        (last_fragment >= s->fragment_count)) {

        av_log(s->avctx, AV_LOG_ERROR, "  vp3:unpack_vlcs(): bad fragment number (%d -> %d ?)\n",
            first_fragment, last_fragment);
        return 0;
    }

    for (i = first_fragment; i <= last_fragment; i++) {

        fragment = &s->all_fragments[s->coded_fragment_list[i]];
        if (fragment->coeff_count > coeff_index)
            continue;

        if (!eob_run) {
            /* decode a VLC into a token */
            token = get_vlc2(gb, table->table, 5, 3);
            debug_vlc(" token = %2d, ", token);
            /* use the token to get a zero run, a coefficient, and an eob run */
            if (token <= 6) {
                eob_run = eob_run_base[token];
                if (eob_run_get_bits[token])
                    eob_run += get_bits(gb, eob_run_get_bits[token]);
                coeff = zero_run = 0;
            } else {
                bits_to_get = coeff_get_bits[token];
                if (!bits_to_get)
                    coeff = coeff_tables[token][0];
                else
                    coeff = coeff_tables[token][get_bits(gb, bits_to_get)];

                zero_run = zero_run_base[token];
                if (zero_run_get_bits[token])
                    zero_run += get_bits(gb, zero_run_get_bits[token]);
            }
        }

        if (!eob_run) {
            fragment->coeff_count += zero_run;
            if (fragment->coeff_count < 64){
                fragment->next_coeff->coeff= coeff;
                fragment->next_coeff->index= perm[fragment->coeff_count++]; //FIXME perm here already?
                fragment->next_coeff->next= s->next_coeff;
                s->next_coeff->next=NULL;
                fragment->next_coeff= s->next_coeff++;
            }
            debug_vlc(" fragment %d coeff = %d\n",
                s->coded_fragment_list[i], fragment->next_coeff[coeff_index]);
        } else {
            fragment->coeff_count |= 128;
            debug_vlc(" fragment %d eob with %d coefficients\n",
                s->coded_fragment_list[i], fragment->coeff_count&127);
            eob_run--;
        }
    }

    return eob_run;
}

/*
 * This function unpacks all of the DCT coefficient data from the
 * bitstream.
 */
static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb)
{
    int i;
    int dc_y_table;
    int dc_c_table;
    int ac_y_table;
    int ac_c_table;
    int residual_eob_run = 0;

    /* fetch the DC table indices */
    dc_y_table = get_bits(gb, 4);
    dc_c_table = get_bits(gb, 4);

    /* unpack the Y plane DC coefficients */
    debug_vp3("  vp3: unpacking Y plane DC coefficients using table %d\n",
        dc_y_table);
    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_y_table], 0,
        s->first_coded_y_fragment, s->last_coded_y_fragment, residual_eob_run);

    /* unpack the C plane DC coefficients */
    debug_vp3("  vp3: unpacking C plane DC coefficients using table %d\n",
        dc_c_table);
    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_c_table], 0,
        s->first_coded_c_fragment, s->last_coded_c_fragment, residual_eob_run);

    /* fetch the AC table indices */
    ac_y_table = get_bits(gb, 4);
    ac_c_table = get_bits(gb, 4);

    /* unpack the group 1 AC coefficients (coeffs 1-5) */
    for (i = 1; i <= 5; i++) {

        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
            i, ac_y_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_1[ac_y_table], i,
            s->first_coded_y_fragment, s->last_coded_y_fragment, residual_eob_run);

        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
            i, ac_c_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_1[ac_c_table], i,
            s->first_coded_c_fragment, s->last_coded_c_fragment, residual_eob_run);
    }

    /* unpack the group 2 AC coefficients (coeffs 6-14) */
    for (i = 6; i <= 14; i++) {

        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
            i, ac_y_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_2[ac_y_table], i,
            s->first_coded_y_fragment, s->last_coded_y_fragment, residual_eob_run);

        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
            i, ac_c_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_2[ac_c_table], i,
            s->first_coded_c_fragment, s->last_coded_c_fragment, residual_eob_run);
    }

    /* unpack the group 3 AC coefficients (coeffs 15-27) */
    for (i = 15; i <= 27; i++) {

        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
            i, ac_y_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_3[ac_y_table], i,
            s->first_coded_y_fragment, s->last_coded_y_fragment, residual_eob_run);

        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
            i, ac_c_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_3[ac_c_table], i,
            s->first_coded_c_fragment, s->last_coded_c_fragment, residual_eob_run);
    }

    /* unpack the group 4 AC coefficients (coeffs 28-63) */
    for (i = 28; i <= 63; i++) {

        debug_vp3("  vp3: unpacking level %d Y plane AC coefficients using table %d\n",
            i, ac_y_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_4[ac_y_table], i,
            s->first_coded_y_fragment, s->last_coded_y_fragment, residual_eob_run);

        debug_vp3("  vp3: unpacking level %d C plane AC coefficients using table %d\n",
            i, ac_c_table);
        residual_eob_run = unpack_vlcs(s, gb, &s->ac_vlc_4[ac_c_table], i,
            s->first_coded_c_fragment, s->last_coded_c_fragment, residual_eob_run);
    }

    return 0;
}

/*
 * This function reverses the DC prediction for each coded fragment in
 * the frame. Much of this function is adapted directly from the original
 * VP3 source code.
 */
#define COMPATIBLE_FRAME(x) \
  (compatible_frame[s->all_fragments[x].coding_method] == current_frame_type)
#define FRAME_CODED(x) (s->all_fragments[x].coding_method != MODE_COPY)
#define DC_COEFF(u) (s->coeffs[u].index ? 0 : s->coeffs[u].coeff) //FIXME do somethin to simplify this

static void reverse_dc_prediction(Vp3DecodeContext *s,
                                  int first_fragment,
                                  int fragment_width,
                                  int fragment_height)
{

#define PUL 8
#define PU 4
#define PUR 2
#define PL 1

    int x, y;
    int i = first_fragment;

    int predicted_dc;

    /* DC values for the left, up-left, up, and up-right fragments */
    int vl, vul, vu, vur;

    /* indices for the left, up-left, up, and up-right fragments */
    int l, ul, u, ur;

    /*
     * The 6 fields mean:
     *   0: up-left multiplier
     *   1: up multiplier
     *   2: up-right multiplier
     *   3: left multiplier
     */
    int predictor_transform[16][4] = {