vqavideo.c

ffmpeg源码分析

    int cbf0_chunk = -1;
    int cbfz_chunk = -1;
    int cbp0_chunk = -1;
    int cbpz_chunk = -1;
    int cpl0_chunk = -1;
    int cplz_chunk = -1;
    int vptz_chunk = -1;

    int x, y;
    int lines = 0;
    int pixel_ptr;
    int vector_index = 0;
    int lobyte = 0;
    int hibyte = 0;
    int lobytes = 0;
    int hibytes = s->decode_buffer_size / 2;

    /* first, traverse through the frame and find the subchunks */
    while (index < s->size) {

        chunk_type = BE_32(&s->buf[index]);
        chunk_size = BE_32(&s->buf[index + 4]);

        switch (chunk_type) {

        case CBF0_TAG:
            cbf0_chunk = index;
            break;

        case CBFZ_TAG:
            cbfz_chunk = index;
            break;

        case CBP0_TAG:
            cbp0_chunk = index;
            break;

        case CBPZ_TAG:
            cbpz_chunk = index;
            break;

        case CPL0_TAG:
            cpl0_chunk = index;
            break;

        case CPLZ_TAG:
            cplz_chunk = index;
            break;

        case VPTZ_TAG:
            vptz_chunk = index;
            break;

        default:
            av_log(s->avctx, AV_LOG_ERROR, "  VQA video: Found unknown chunk type: %c%c%c%c (%08X)\n",
            (chunk_type >> 24) & 0xFF,
            (chunk_type >> 16) & 0xFF,
            (chunk_type >>  8) & 0xFF,
            (chunk_type >>  0) & 0xFF,
            chunk_type);
            break;
        }

        byte_skip = chunk_size & 0x01;
        index += (CHUNK_PREAMBLE_SIZE + chunk_size + byte_skip);
    }

    /* next, deal with the palette */
    if ((cpl0_chunk != -1) && (cplz_chunk != -1)) {

        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "  VQA video: problem: found both CPL0 and CPLZ chunks\n");
        return;
    }

    /* decompress the palette chunk */
    if (cplz_chunk != -1) {

/* yet to be handled */

    }

    /* convert the RGB palette into the machine's endian format */
    if (cpl0_chunk != -1) {

        chunk_size = BE_32(&s->buf[cpl0_chunk + 4]);
        /* sanity check the palette size */
        if (chunk_size / 3 > 256) {
            av_log(s->avctx, AV_LOG_ERROR, "  VQA video: problem: found a palette chunk with %d colors\n",
                chunk_size / 3);
            return;
        }
        cpl0_chunk += CHUNK_PREAMBLE_SIZE;
        for (i = 0; i < chunk_size / 3; i++) {
            /* scale by 4 to transform 6-bit palette -> 8-bit */
            r = s->buf[cpl0_chunk++] * 4;
            g = s->buf[cpl0_chunk++] * 4;
            b = s->buf[cpl0_chunk++] * 4;
            s->palette[i] = (r << 16) | (g << 8) | (b);
        }
    }

    /* next, look for a full codebook */
    if ((cbf0_chunk != -1) && (cbfz_chunk != -1)) {

        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "  VQA video: problem: found both CBF0 and CBFZ chunks\n");
        return;
    }

    /* decompress the full codebook chunk */
    if (cbfz_chunk != -1) {

        chunk_size = BE_32(&s->buf[cbfz_chunk + 4]);
        cbfz_chunk += CHUNK_PREAMBLE_SIZE;
        decode_format80(&s->buf[cbfz_chunk], chunk_size,
            s->codebook, s->codebook_size, 0);
    }

    /* copy a full codebook */
    if (cbf0_chunk != -1) {

        chunk_size = BE_32(&s->buf[cbf0_chunk + 4]);
        /* sanity check the full codebook size */
        if (chunk_size > MAX_CODEBOOK_SIZE) {
            av_log(s->avctx, AV_LOG_ERROR, "  VQA video: problem: CBF0 chunk too large (0x%X bytes)\n",
                chunk_size);
            return;
        }
        cbf0_chunk += CHUNK_PREAMBLE_SIZE;

        memcpy(s->codebook, &s->buf[cbf0_chunk], chunk_size);
    }

    /* decode the frame */
    if (vptz_chunk == -1) {

        /* something is wrong if there is no VPTZ chunk */
        av_log(s->avctx, AV_LOG_ERROR, "  VQA video: problem: no VPTZ chunk found\n");
        return;
    }

    chunk_size = BE_32(&s->buf[vptz_chunk + 4]);
    vptz_chunk += CHUNK_PREAMBLE_SIZE;
    decode_format80(&s->buf[vptz_chunk], chunk_size,
        s->decode_buffer, s->decode_buffer_size, 1);

    /* render the final PAL8 frame */
    if (s->vector_height == 4)
        index_shift = 4;
    else
        index_shift = 3;
    for (y = 0; y < s->frame.linesize[0] * s->height;
        y += s->frame.linesize[0] * s->vector_height) {

        for (x = y; x < y + s->width; x += 4, lobytes++, hibytes++) {
            pixel_ptr = x;

            /* get the vector index, the method for which varies according to
             * VQA file version */
            switch (s->vqa_version) {

            case 1:
/* still need sample media for this case (only one game, "Legend of
 * Kyrandia III : Malcolm's Revenge", is known to use this version) */
                lines = 0;
                break;

            case 2:
                lobyte = s->decode_buffer[lobytes];
                hibyte = s->decode_buffer[hibytes];
                vector_index = (hibyte << 8) | lobyte;
                vector_index <<= index_shift;
                lines = s->vector_height;
                break;

            case 3:
/* not implemented yet */
                lines = 0;
                break;
            }

            while (lines--) {
                s->frame.data[0][pixel_ptr + 0] = s->codebook[vector_index++];
                s->frame.data[0][pixel_ptr + 1] = s->codebook[vector_index++];
                s->frame.data[0][pixel_ptr + 2] = s->codebook[vector_index++];
                s->frame.data[0][pixel_ptr + 3] = s->codebook[vector_index++];
                pixel_ptr += s->frame.linesize[0];
            }
        }
    }

    /* handle partial codebook */
    if ((cbp0_chunk != -1) && (cbpz_chunk != -1)) {
        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "  VQA video: problem: found both CBP0 and CBPZ chunks\n");
        return;
    }

    if (cbp0_chunk != -1) {

        chunk_size = BE_32(&s->buf[cbp0_chunk + 4]);
        cbp0_chunk += CHUNK_PREAMBLE_SIZE;

        /* accumulate partial codebook */
        memcpy(&s->next_codebook_buffer[s->next_codebook_buffer_index],
            &s->buf[cbp0_chunk], chunk_size);
        s->next_codebook_buffer_index += chunk_size;

        s->partial_countdown--;
        if (s->partial_countdown == 0) {

            /* time to replace codebook */
            memcpy(s->codebook, s->next_codebook_buffer,
                s->next_codebook_buffer_index);

            /* reset accounting */
            s->next_codebook_buffer_index = 0;
            s->partial_countdown = s->partial_count;
        }
    }

    if (cbpz_chunk != -1) {

        chunk_size = BE_32(&s->buf[cbpz_chunk + 4]);
        cbpz_chunk += CHUNK_PREAMBLE_SIZE;

        /* accumulate partial codebook */
        memcpy(&s->next_codebook_buffer[s->next_codebook_buffer_index],
            &s->buf[cbpz_chunk], chunk_size);
        s->next_codebook_buffer_index += chunk_size;

        s->partial_countdown--;
        if (s->partial_countdown == 0) {

            /* decompress codebook */
            decode_format80(s->next_codebook_buffer,
                s->next_codebook_buffer_index,
                s->codebook, s->codebook_size, 0);

            /* reset accounting */
            s->next_codebook_buffer_index = 0;
            s->partial_countdown = s->partial_count;
        }
    }
}

static int vqa_decode_frame(AVCodecContext *avctx,
                            void *data, int *data_size,
                            uint8_t *buf, int buf_size)
{
    VqaContext *s = (VqaContext *)avctx->priv_data;

    s->buf = buf;
    s->size = buf_size;

    if (s->frame.data[0])
        avctx->release_buffer(avctx, &s->frame);

    if (avctx->get_buffer(avctx, &s->frame)) {
        av_log(s->avctx, AV_LOG_ERROR, "  VQA Video: get_buffer() failed\n");
        return -1;
    }

    vqa_decode_chunk(s);

    /* make the palette available on the way out */
    memcpy(s->frame.data[1], s->palette, PALETTE_COUNT * 4);
    s->frame.palette_has_changed = 1;

    *data_size = sizeof(AVFrame);
    *(AVFrame*)data = s->frame;

    /* report that the buffer was completely consumed */
    return buf_size;
}

static int vqa_decode_end(AVCodecContext *avctx)
{
    VqaContext *s = (VqaContext *)avctx->priv_data;

    av_free(s->codebook);
    av_free(s->next_codebook_buffer);
    av_free(s->decode_buffer);

    if (s->frame.data[0])
        avctx->release_buffer(avctx, &s->frame);

    return 0;
}

AVCodec vqa_decoder = {
    "vqavideo",
    CODEC_TYPE_VIDEO,
    CODEC_ID_WS_VQA,
    sizeof(VqaContext),
    vqa_decode_init,
    NULL,
    vqa_decode_end,
    vqa_decode_frame,
    CODEC_CAP_DR1,
};