truemotion1.c

arm平台下的H264编码和解码源代码

        if (compression_types[header.compression].algorithm == ALGO_RGB24H)
        {
            av_log(s->avctx, AV_LOG_ERROR, "24bit compression not yet supported\n");
        }
        else
            gen_vector_table(s, sel_vector_table);
    }

    /* set up pointers to the other key data chunks */
    s->mb_change_bits = s->buf + header.header_size;
    if (s->flags & FLAG_KEYFRAME) {
        /* no change bits specified for a keyframe; only index bytes */
        s->index_stream = s->mb_change_bits;
    } else {
        /* one change bit per 4x4 block */
        s->index_stream = s->mb_change_bits + 
            (s->mb_change_bits_row_size * (s->avctx->height >> 2));
    }
    s->index_stream_size = s->size - (s->index_stream - s->buf);

    s->last_deltaset = header.deltaset;
    s->last_vectable = header.vectable;
    s->compression = header.compression;
    s->block_width = compression_types[header.compression].block_width;
    s->block_height = compression_types[header.compression].block_height;
    s->block_type = compression_types[header.compression].block_type;

    return header.header_size;    
}

static int truemotion1_decode_init(AVCodecContext *avctx)
{
    TrueMotion1Context *s = (TrueMotion1Context *)avctx->priv_data;

    s->avctx = avctx;

    avctx->pix_fmt = PIX_FMT_RGB555;
    avctx->has_b_frames = 0;
    s->frame.data[0] = s->prev_frame.data[0] = NULL;

    /* there is a vertical predictor for each pixel in a line; each vertical
     * predictor is 0 to start with */
    s->vert_pred = 
        (unsigned int *)av_malloc(s->avctx->width * sizeof(unsigned short));

    return 0;
}

#define GET_NEXT_INDEX() \
{\
    if (index_stream_index >= s->index_stream_size) { \
        av_log(s->avctx, AV_LOG_INFO, " help! truemotion1 decoder went out of bounds\n"); \
        return; \
    } \
    index = s->index_stream[index_stream_index++] * 4; \
}

#define APPLY_C_PREDICTOR() \
    predictor_pair = s->c_predictor_table[index]; \
    horiz_pred += (predictor_pair >> 1); \
    if (predictor_pair & 1) { \
        GET_NEXT_INDEX() \
        if (!index) { \
            GET_NEXT_INDEX() \
            predictor_pair = s->c_predictor_table[index]; \
            horiz_pred += ((predictor_pair >> 1) * 5); \
            if (predictor_pair & 1) \
                GET_NEXT_INDEX() \
            else \
                index++; \
        } \
    } else \
        index++;

#define APPLY_Y_PREDICTOR() \
    predictor_pair = s->y_predictor_table[index]; \
    horiz_pred += (predictor_pair >> 1); \
    if (predictor_pair & 1) { \
        GET_NEXT_INDEX() \
        if (!index) { \
            GET_NEXT_INDEX() \
            predictor_pair = s->y_predictor_table[index]; \
            horiz_pred += ((predictor_pair >> 1) * 5); \
            if (predictor_pair & 1) \
                GET_NEXT_INDEX() \
            else \
                index++; \
        } \
    } else \
        index++;

#define OUTPUT_PIXEL_PAIR() \
    *current_pixel_pair = *vert_pred + horiz_pred; \
    *vert_pred++ = *current_pixel_pair++; \
    prev_pixel_pair++;

static void truemotion1_decode_16bit(TrueMotion1Context *s)
{
    int y;
    int pixels_left;  /* remaining pixels on this line */
    unsigned int predictor_pair;
    unsigned int horiz_pred;
    unsigned int *vert_pred;
    unsigned int *current_pixel_pair;
    unsigned int *prev_pixel_pair;
    unsigned char *current_line = s->frame.data[0];
    unsigned char *prev_line = s->prev_frame.data[0];
    int keyframe = s->flags & FLAG_KEYFRAME;

    /* these variables are for managing the stream of macroblock change bits */
    unsigned char *mb_change_bits = s->mb_change_bits;
    unsigned char mb_change_byte;
    unsigned char mb_change_byte_mask;
    int mb_change_index;

    /* these variables are for managing the main index stream */
    int index_stream_index = 0;  /* yes, the index into the index stream */
    int index;

    /* clean out the line buffer */
    memset(s->vert_pred, 0, s->avctx->width * sizeof(unsigned short));

    GET_NEXT_INDEX();

    for (y = 0; y < s->avctx->height; y++) {

        /* re-init variables for the next line iteration */
        horiz_pred = 0;
        current_pixel_pair = (unsigned int *)current_line;
        prev_pixel_pair = (unsigned int *)prev_line;
        vert_pred = s->vert_pred;
        mb_change_index = 0;
        mb_change_byte = mb_change_bits[mb_change_index++];
        mb_change_byte_mask = 0x01;
        pixels_left = s->avctx->width;

        while (pixels_left > 0) {

            if (keyframe || ((mb_change_byte & mb_change_byte_mask) == 0)) {

                switch (y & 3) {
                case 0:
                    /* if macroblock width is 2, apply C-Y-C-Y; else 
                     * apply C-Y-Y */
                    if (s->block_width == 2) {
                        APPLY_C_PREDICTOR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                        APPLY_C_PREDICTOR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                    } else {
                        APPLY_C_PREDICTOR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                    }
                    break;

                case 1:
                case 3:
                    /* always apply 2 Y predictors on these iterations */
                    APPLY_Y_PREDICTOR();
                    OUTPUT_PIXEL_PAIR();
                    APPLY_Y_PREDICTOR();
                    OUTPUT_PIXEL_PAIR();
                    break;

                case 2:
                    /* this iteration might be C-Y-C-Y, Y-Y, or C-Y-Y 
                     * depending on the macroblock type */
                    if (s->block_type == BLOCK_2x2) {
                        APPLY_C_PREDICTOR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                        APPLY_C_PREDICTOR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                    } else if (s->block_type == BLOCK_4x2) {
                        APPLY_C_PREDICTOR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                    } else {
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                        APPLY_Y_PREDICTOR();
                        OUTPUT_PIXEL_PAIR();
                    }
                    break;
                }

            } else {

                /* skip (copy) four pixels, but reassign the horizontal 
                 * predictor */
                *current_pixel_pair = *prev_pixel_pair++;
                *vert_pred++ = *current_pixel_pair++;
                *current_pixel_pair = *prev_pixel_pair++;
                horiz_pred = *current_pixel_pair - *vert_pred;
                *vert_pred++ = *current_pixel_pair++;
                
            }

            if (!keyframe) {
                mb_change_byte_mask <<= 1;

                /* next byte */
                if (!mb_change_byte_mask) {
                    mb_change_byte = mb_change_bits[mb_change_index++];
                    mb_change_byte_mask = 0x01;
                }
            }

            pixels_left -= 4;
        }

        /* next change row */
        if (((y + 1) & 3) == 0)
            mb_change_bits += s->mb_change_bits_row_size;

        current_line += s->frame.linesize[0];
        prev_line += s->prev_frame.linesize[0];
    }
}

static int truemotion1_decode_frame(AVCodecContext *avctx,
                                    void *data, int *data_size,
                                    uint8_t *buf, int buf_size)
{
    TrueMotion1Context *s = (TrueMotion1Context *)avctx->priv_data;

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

    s->frame.reference = 1;
    if (avctx->get_buffer(avctx, &s->frame) < 0) {
        av_log(s->avctx, AV_LOG_ERROR, "truemotion1: get_buffer() failed\n");
        return -1;
    }

    /* no supplementary picture */
    if (buf_size == 0)
        return 0;

    *data_size = 0;
    
    if (truemotion1_decode_header(s) == -1)
        return -1;

    /* check for a do-nothing frame and copy the previous frame */
    if (compression_types[s->compression].algorithm == ALGO_NOP)
    {
        memcpy(s->frame.data[0], s->prev_frame.data[0],
            s->frame.linesize[0] * s->avctx->height);
    } else if (compression_types[s->compression].algorithm == ALGO_RGB24H) {
        av_log(s->avctx, AV_LOG_ERROR, "24bit compression not yet supported\n");
    } else {
        truemotion1_decode_16bit(s);
    }

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

    /* shuffle frames */
    s->prev_frame = s->frame;

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

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

static int truemotion1_decode_end(AVCodecContext *avctx)
{
    TrueMotion1Context *s = (TrueMotion1Context *)avctx->priv_data;

    /* release the last frame */
    if (s->prev_frame.data[0])
        avctx->release_buffer(avctx, &s->prev_frame);

    av_free(s->vert_pred);

    return 0;
}

AVCodec truemotion1_decoder = {
    "truemotion1",
    CODEC_TYPE_VIDEO,
    CODEC_ID_TRUEMOTION1,
    sizeof(TrueMotion1Context),
    truemotion1_decode_init,
    NULL,
    truemotion1_decode_end,
    truemotion1_decode_frame,
    CODEC_CAP_DR1,
};