/**
 * Expand an RLE row into a channel.
 * @param in_buf input buffer
 * @param in_end end of input buffer
 * @param out_buf Points to one line after the output buffer.
 * @param out_end end of line in output buffer
 * @param pixelstride pixel stride of input buffer
 * @return size of output in bytes, -1 if buffer overflows
 */
static int expand_rle_row(const uint8_t *in_buf, const uint8_t* in_end,
            unsigned char *out_buf, uint8_t* out_end, int pixelstride)
{
    unsigned char pixel, count;
    unsigned char *orig = out_buf;

    while (1) {
        if(in_buf + 1 > in_end) return -1;
        pixel = bytestream_get_byte(&in_buf);
        if (!(count = (pixel & 0x7f))) {
            return (out_buf - orig) / pixelstride;
        }

        /* Check for buffer overflow. */
        if(out_buf + pixelstride * count >= out_end) return -1;

        if (pixel & 0x80) {
            while (count--) {
                *out_buf = bytestream_get_byte(&in_buf);
                out_buf += pixelstride;
            }
        } else {
            pixel = bytestream_get_byte(&in_buf);

            while (count--) {
                *out_buf = pixel;
                out_buf += pixelstride;
            }
        }
    }
}

/**
 * Parse the palette segment packet.
 *
 * The palette segment contains details of the palette,
 * a maximum of 256 colors can be defined.
 *
 * @param avctx contains the current codec context
 * @param buf pointer to the packet to process
 * @param buf_size size of packet to process
 */
static void parse_palette_segment(AVCodecContext *avctx,
                                  const uint8_t *buf, int buf_size)
{
    PGSSubContext *ctx = avctx->priv_data;

    const uint8_t *buf_end = buf + buf_size;
    const uint8_t *cm      = ff_cropTbl + MAX_NEG_CROP;
    int color_id;
    int y, cb, cr, alpha;
    int r, g, b, r_add, g_add, b_add;

    /* Skip two null bytes */
    buf += 2;

    while (buf < buf_end) {
        color_id  = bytestream_get_byte(&buf);
        y         = bytestream_get_byte(&buf);
        cr        = bytestream_get_byte(&buf);
        cb        = bytestream_get_byte(&buf);
        alpha     = bytestream_get_byte(&buf);

        YUV_TO_RGB1(cb, cr);
        YUV_TO_RGB2(r, g, b, y);

        av_dlog(avctx, "Color %d := (%d,%d,%d,%d)\n", color_id, r, g, b, alpha);

        /* Store color in palette */
        ctx->clut[color_id] = RGBA(r,g,b,alpha);
    }
}

/**
 * Parse the presentation segment packet.
 *
 * The presentation segment contains details on the video
 * width, video height, x & y subtitle position.
 *
 * @param avctx contains the current codec context
 * @param buf pointer to the packet to process
 * @param buf_size size of packet to process
 * @todo TODO: Implement cropping
 * @todo TODO: Implement forcing of subtitles
 */
static void parse_presentation_segment(AVCodecContext *avctx,
                                       const uint8_t *buf, int buf_size)
{
    PGSSubContext *ctx = avctx->priv_data;

    int x, y;

    int w = bytestream_get_be16(&buf);
    int h = bytestream_get_be16(&buf);

    av_dlog(avctx, "Video Dimensions %dx%d\n",
            w, h);
    if (av_image_check_size(w, h, 0, avctx) >= 0)
        avcodec_set_dimensions(avctx, w, h);

    /* Skip 1 bytes of unknown, frame rate? */
    buf++;

    ctx->presentation.id_number = bytestream_get_be16(&buf);

    /*
     * Skip 3 bytes of unknown:
     *     state
     *     palette_update_flag (0x80),
     *     palette_id_to_use,
     */
    buf += 3;

    ctx->presentation.object_number = bytestream_get_byte(&buf);
    ctx->presentation.composition_flag = 0;
    if (!ctx->presentation.object_number)
        return;

    /*
     * Skip 3 bytes of unknown:
     *     object_id_ref (2 bytes),
     *     window_id_ref,
     */
    buf += 3;
    ctx->presentation.composition_flag = bytestream_get_byte(&buf);

    x = bytestream_get_be16(&buf);
    y = bytestream_get_be16(&buf);

    /* TODO If cropping, cropping_x, cropping_y, cropping_width, cropping_height (all 2 bytes).*/

    av_dlog(avctx, "Subtitle Placement x=%d, y=%d\n", x, y);

    if (x > avctx->width || y > avctx->height) {
        av_log(avctx, AV_LOG_ERROR, "Subtitle out of video bounds. x = %d, y = %d, video width = %d, video height = %d.\n",
               x, y, avctx->width, avctx->height);
        x = 0; y = 0;
    }

    /* Fill in dimensions */
    ctx->presentation.x = x;
    ctx->presentation.y = y;
}

static int gif_read_header1(GifState *s)
{
    uint8_t sig[6];
    int v, n;
    int background_color_index;

    if (s->bytestream_end < s->bytestream + 13)
        return AVERROR_INVALIDDATA;

    /* read gif signature */
    bytestream_get_buffer(&s->bytestream, sig, 6);
    if (memcmp(sig, gif87a_sig, 6) != 0 &&
        memcmp(sig, gif89a_sig, 6) != 0)
        return AVERROR_INVALIDDATA;

    /* read screen header */
    s->transparent_color_index = -1;
    s->screen_width = bytestream_get_le16(&s->bytestream);
    s->screen_height = bytestream_get_le16(&s->bytestream);
    if(   (unsigned)s->screen_width  > 32767
       || (unsigned)s->screen_height > 32767){
        av_log(s->avctx, AV_LOG_ERROR, "picture size too large\n");
        return AVERROR_INVALIDDATA;
    }

    av_fast_malloc(&s->idx_line, &s->idx_line_size, s->screen_width);
    if (!s->idx_line)
        return AVERROR(ENOMEM);

    v = bytestream_get_byte(&s->bytestream);
    s->color_resolution = ((v & 0x70) >> 4) + 1;
    s->has_global_palette = (v & 0x80);
    s->bits_per_pixel = (v & 0x07) + 1;
    background_color_index = bytestream_get_byte(&s->bytestream);
    n = bytestream_get_byte(&s->bytestream);
    if (n) {
        s->avctx->sample_aspect_ratio.num = n + 15;
        s->avctx->sample_aspect_ratio.den = 64;
    }

    av_dlog(s->avctx, "screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
           s->screen_width, s->screen_height, s->bits_per_pixel,
           s->has_global_palette);

    if (s->has_global_palette) {
        s->background_color_index = background_color_index;
        n = 1 << s->bits_per_pixel;
        if (s->bytestream_end < s->bytestream + n * 3)
            return AVERROR_INVALIDDATA;

        gif_read_palette(&s->bytestream, s->global_palette, n);
        s->bg_color = s->global_palette[s->background_color_index];
    } else
        s->background_color_index = -1;

    return 0;
}

/**
 * Decode the RLE data.
 *
 * The subtitle is stored as an Run Length Encoded image.
 *
 * @param avctx contains the current codec context
 * @param sub pointer to the processed subtitle data
 * @param buf pointer to the RLE data to process
 * @param buf_size size of the RLE data to process
 */
static int decode_rle(AVCodecContext *avctx, AVSubtitle *sub,
                      const uint8_t *buf, unsigned int buf_size)
{
    const uint8_t *rle_bitmap_end;
    int pixel_count, line_count;

    rle_bitmap_end = buf + buf_size;

    sub->rects[0]->pict.data[0] = av_malloc(sub->rects[0]->w * sub->rects[0]->h);

    if (!sub->rects[0]->pict.data[0])
        return -1;

    pixel_count = 0;
    line_count  = 0;

    while (buf < rle_bitmap_end && line_count < sub->rects[0]->h) {
        uint8_t flags, color;
        int run;

        color = bytestream_get_byte(&buf);
        run   = 1;

        if (color == 0x00) {
            flags = bytestream_get_byte(&buf);
            run   = flags & 0x3f;
            if (flags & 0x40)
                run = (run << 8) + bytestream_get_byte(&buf);
            color = flags & 0x80 ? bytestream_get_byte(&buf) : 0;
        }

        if (run > 0 && pixel_count + run <= sub->rects[0]->w * sub->rects[0]->h) {
            memset(sub->rects[0]->pict.data[0] + pixel_count, color, run);
            pixel_count += run;
        } else if (!run) {
            /*
             * New Line. Check if correct pixels decoded, if not display warning
             * and adjust bitmap pointer to correct new line position.
             */
            if (pixel_count % sub->rects[0]->w > 0)
                av_log(avctx, AV_LOG_ERROR, "Decoded %d pixels, when line should be %d pixels\n",
                       pixel_count % sub->rects[0]->w, sub->rects[0]->w);
            line_count++;
        }
    }

    if (pixel_count < sub->rects[0]->w * sub->rects[0]->h) {
        av_log(avctx, AV_LOG_ERROR, "Insufficient RLE data for subtitle\n");
        return -1;
    }

    av_dlog(avctx, "Pixel Count = %d, Area = %d\n", pixel_count, sub->rects[0]->w * sub->rects[0]->h);

    return 0;
}

static void tgq_decode_mb(TgqContext *s, int mb_y, int mb_x, const uint8_t **bs, const uint8_t *buf_end){
    int mode;
    int i;
    int8_t dc[6];

    mode = bytestream_get_byte(bs);
    if (mode>buf_end-*bs) {
        av_log(s->avctx, AV_LOG_ERROR, "truncated macroblock\n");
        return;
    }

    if (mode>12) {
        GetBitContext gb;
        init_get_bits(&gb, *bs, mode*8);
        for(i=0; i<6; i++)
            tgq_decode_block(s, s->block[i], &gb);
        tgq_idct_put_mb(s, s->block, mb_x, mb_y);
    }else{
        if (mode==3) {
            memset(dc, (*bs)[0], 4);
            dc[4] = (*bs)[1];
            dc[5] = (*bs)[2];
        }else if (mode==6) {
            memcpy(dc, *bs, 6);
        }else if (mode==12) {
            for(i=0; i<6; i++)
                dc[i] = (*bs)[i*2];
        }else{
            av_log(s->avctx, AV_LOG_ERROR, "unsupported mb mode %i\n", mode);
        }
        tgq_idct_put_mb_dconly(s, mb_x, mb_y, dc);
    }
    *bs += mode;
}

static int gif_parse_next_image(GifState *s)
{
    int ret, code;

    for (;;) {
        code = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
        dprintf("gif: code=%02x '%c'\n", code, code);
#endif
        switch (code) {
        case ',':
            if (gif_read_image(s) < 0)
                return -1;
            ret = 0;
            goto the_end;
        case ';':
            /* end of image */
            ret = -1;
            goto the_end;
        case '!':
            if (gif_read_extension(s) < 0)
                return -1;
            break;
        case EOF:
        default:
            /* error or errneous EOF */
            ret = -1;
            goto the_end;
        }
    }
  the_end:
    return ret;
}

static int gif_parse_next_image(GifState *s, int *got_picture)
{
    int ret;
    *got_picture = sizeof(AVPicture);
    while (s->bytestream < s->bytestream_end) {
        int code = bytestream_get_byte(&s->bytestream);

        av_dlog(s->avctx, "code=%02x '%c'\n", code, code);

        switch (code) {
        case GIF_IMAGE_SEPARATOR:
            return gif_read_image(s);
        case GIF_EXTENSION_INTRODUCER:
            if ((ret = gif_read_extension(s)) < 0)
                return ret;
            break;
        case GIF_TRAILER:
            /* end of image */
            *got_picture = 0;
            return 0;
        default:
            /* erroneous block label */
            return AVERROR_INVALIDDATA;
        }
    }
    return AVERROR_EOF;
}

/**
 * Parse the presentation segment packet.
 *
 * The presentation segment contains details on the video
 * width, video height, x & y subtitle position.
 *
 * @param avctx contains the current codec context
 * @param buf pointer to the packet to process
 * @param buf_size size of packet to process
 * @todo TODO: Implement cropping
 * @todo TODO: Implement forcing of subtitles
 * @todo TODO: Blanking of subtitle
 */
static void parse_presentation_segment(AVCodecContext *avctx,
                                       const uint8_t *buf, int buf_size)
{
    PGSSubContext *ctx = avctx->priv_data;

    int x, y;
    uint8_t block;

    int w = bytestream_get_be16(&buf);
    int h = bytestream_get_be16(&buf);

    dprintf(avctx, "Video Dimensions %dx%d\n",
            w, h);
    if (av_image_check_size(w, h, 0, avctx) >= 0)
        avcodec_set_dimensions(avctx, w, h);

    /* Skip 1 bytes of unknown, frame rate? */
    buf++;

    ctx->presentation.id_number = bytestream_get_be16(&buf);

    /* Next byte is the state. */
    block = bytestream_get_byte(&buf);;
    if (block == 0x80) {
        /*
         * Skip 7 bytes of unknown:
         *     palette_update_flag (0x80),
         *     palette_id_to_use,
         *     Object Number (if > 0 determines if more data to process),
         *     object_id_ref (2 bytes),
         *     window_id_ref,
         *     composition_flag (0x80 - object cropped, 0x40 - object forced)
         */
        buf += 7;

        x = bytestream_get_be16(&buf);
        y = bytestream_get_be16(&buf);

        /* TODO If cropping, cropping_x, cropping_y, cropping_width, cropping_height (all 2 bytes).*/

        dprintf(avctx, "Subtitle Placement x=%d, y=%d\n", x, y);

        if (x > avctx->width || y > avctx->height) {
            av_log(avctx, AV_LOG_ERROR, "Subtitle out of video bounds. x = %d, y = %d, video width = %d, video height = %d.\n",
                   x, y, avctx->width, avctx->height);
            x = 0; y = 0;
        }

        /* Fill in dimensions */
        ctx->presentation.x = x;
        ctx->presentation.y = y;
    } else if (block == 0x00) {
        /* TODO: Blank context as subtitle should not be displayed.
         *       If the subtitle is blanked now the subtitle is not
         *       on screen long enough to read, due to a delay in
         *       initial display timing.
         */
    }
}

static int gif_read_header1(GifState *s)
{
    uint8_t sig[6];
    int v, n;
    int has_global_palette;

    if (s->bytestream_end < s->bytestream + 13)
        return -1;

    /* read gif signature */
    bytestream_get_buffer(&s->bytestream, sig, 6);
    if (memcmp(sig, gif87a_sig, 6) != 0 &&
        memcmp(sig, gif89a_sig, 6) != 0)
        return -1;

    /* read screen header */
    s->transparent_color_index = -1;
    s->screen_width = bytestream_get_le16(&s->bytestream);
    s->screen_height = bytestream_get_le16(&s->bytestream);
    if(   (unsigned)s->screen_width  > 32767
       || (unsigned)s->screen_height > 32767){
        av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
        return -1;
    }

    v = bytestream_get_byte(&s->bytestream);
    s->color_resolution = ((v & 0x70) >> 4) + 1;
    has_global_palette = (v & 0x80);
    s->bits_per_pixel = (v & 0x07) + 1;
    s->background_color_index = bytestream_get_byte(&s->bytestream);
    bytestream_get_byte(&s->bytestream);                /* ignored */
#ifdef DEBUG
    dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
           s->screen_width, s->screen_height, s->bits_per_pixel,
           has_global_palette);
#endif
    if (has_global_palette) {
        n = 1 << s->bits_per_pixel;
        if (s->bytestream_end < s->bytestream + n * 3)
            return -1;
        bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
    }
    return 0;
}

void ff_flac_parse_block_header(const uint8_t *block_header,
                                int *last, int *type, int *size)
{
    int tmp = bytestream_get_byte(&block_header);
    if (last)
        *last = tmp & 0x80;
    if (type)
        *type = tmp & 0x7F;
    if (size)
        *size = bytestream_get_be24(&block_header);
}

/**
 * Parses the picture segment packet.
 *
 * The picture segment contains details on the sequence id,
 * width, height and Run Length Encoded (RLE) bitmap data.
 *
 * @param avctx contains the current codec context
 * @param buf pointer to the packet to process
 * @param buf_size size of packet to process
 * @todo TODO: Enable support for RLE data over multiple packets
 */
static int parse_picture_segment(AVCodecContext *avctx,
                                  const uint8_t *buf, int buf_size)
{
    PGSSubContext *ctx = avctx->priv_data;

    uint8_t sequence_desc;
    unsigned int rle_bitmap_len, width, height;

    /* skip 3 unknown bytes: Object ID (2 bytes), Version Number */
    buf += 3;

    /* Read the Sequence Description to determine if start of RLE data or appended to previous RLE */
    sequence_desc = bytestream_get_byte(&buf);

    if (!(sequence_desc & 0x80)) {
        av_log(avctx, AV_LOG_ERROR, "Decoder does not support object data over multiple packets.\n");
        return -1;
    }

    /* Decode rle bitmap length */
    rle_bitmap_len = bytestream_get_be24(&buf);

    /* Check to ensure we have enough data for rle_bitmap_length if just a single packet */
    if (rle_bitmap_len > buf_size - 7) {
        av_log(avctx, AV_LOG_ERROR, "Not enough RLE data for specified length of %d.\n", rle_bitmap_len);
        return -1;
    }

    ctx->picture.rle_data_len = rle_bitmap_len;

    /* Get bitmap dimensions from data */
    width  = bytestream_get_be16(&buf);
    height = bytestream_get_be16(&buf);

    /* Make sure the bitmap is not too large */
    if (ctx->presentation.video_w < width || ctx->presentation.video_h < height) {
        av_log(avctx, AV_LOG_ERROR, "Bitmap dimensions larger then video.\n");
        return -1;
    }

    ctx->picture.w = width;
    ctx->picture.h = height;

    av_fast_malloc(&ctx->picture.rle, &ctx->picture.rle_buffer_size, rle_bitmap_len);

    if (!ctx->picture.rle)
        return -1;

    memcpy(ctx->picture.rle, buf, rle_bitmap_len);

    return 0;
}

static int gif_read_extension(GifState *s)
{
    int ext_code, ext_len, i, gce_flags, gce_transparent_index;

    /* extension */
    ext_code = bytestream_get_byte(&s->bytestream);
    ext_len = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
    dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
#endif
    switch(ext_code) {
    case 0xf9:
        if (ext_len != 4)
            goto discard_ext;
        s->transparent_color_index = -1;
        gce_flags = bytestream_get_byte(&s->bytestream);
        s->gce_delay = bytestream_get_le16(&s->bytestream);
        gce_transparent_index = bytestream_get_byte(&s->bytestream);
        if (gce_flags & 0x01)
            s->transparent_color_index = gce_transparent_index;
        else
            s->transparent_color_index = -1;
        s->gce_disposal = (gce_flags >> 2) & 0x7;
#ifdef DEBUG
        dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
               gce_flags, s->gce_delay,
               s->transparent_color_index, s->gce_disposal);
#endif
        ext_len = bytestream_get_byte(&s->bytestream);
        break;
    }

    /* NOTE: many extension blocks can come after */
 discard_ext:
    while (ext_len != 0) {
        for (i = 0; i < ext_len; i++)
            bytestream_get_byte(&s->bytestream);
        ext_len = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
        dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
#endif
    }
    return 0;
}

static int mimic_decode_frame(AVCodecContext *avctx, void *data,
                              int *data_size, const uint8_t *buf, int buf_size)
{
    MimicContext *ctx = avctx->priv_data;
    int is_pframe;
    int width, height;
    int quality, num_coeffs;
    int swap_buf_size = buf_size - MIMIC_HEADER_SIZE;

    if(buf_size < MIMIC_HEADER_SIZE) {
        av_log(avctx, AV_LOG_ERROR, "insufficient data\n");
        return -1;
    }

    buf       += 2; /* some constant (always 256) */
    quality    = bytestream_get_le16(&buf);
    width      = bytestream_get_le16(&buf);
    height     = bytestream_get_le16(&buf);
    buf       += 4; /* some constant */
    is_pframe  = bytestream_get_le32(&buf);
    num_coeffs = bytestream_get_byte(&buf);
    buf       += 3; /* some constant */

    if(!ctx->avctx) {
        int i;

        if(!(width == 160 && height == 120) &&
           !(width == 320 && height == 240)) {
            av_log(avctx, AV_LOG_ERROR, "invalid width/height!\n");
            return -1;
        }

        ctx->avctx     = avctx;
        avctx->width   = width;
        avctx->height  = height;
        avctx->pix_fmt = PIX_FMT_YUV420P;
        for(i = 0; i < 3; i++) {
            ctx->num_vblocks[i] = -((-height) >> (3 + !!i));
            ctx->num_hblocks[i] =     width   >> (3 + !!i) ;
        }
    } else if(width != ctx->avctx->width || height != ctx->avctx->height) {

static int gif_parse_next_image(GifState *s)
{
    while (s->bytestream < s->bytestream_end) {
        int code = bytestream_get_byte(&s->bytestream);
#ifdef DEBUG
        dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
#endif
        switch (code) {
        case ',':
            return gif_read_image(s);
        case '!':
            if (gif_read_extension(s) < 0)
                return -1;
            break;
        case ';':
            /* end of image */
        default:
            /* error or erroneous EOF */
            return -1;
        }
    }
    return -1;
}

static int gif_parse_next_image(GifState *s, AVFrame *frame)
{
    while (s->bytestream < s->bytestream_end) {
        int code = bytestream_get_byte(&s->bytestream);
        int ret;

        av_dlog(s->avctx, "gif: code=%02x '%c'\n", code, code);

        switch (code) {
        case ',':
            return gif_read_image(s, frame);
        case '!':
            if ((ret = gif_read_extension(s)) < 0)
                return ret;
            break;
        case ';':
            /* end of image */
        default:
            /* error or erroneous EOF */
            return AVERROR_INVALIDDATA;
        }
    }
    return AVERROR_INVALIDDATA;
}

static int gif_read_extension(GifState *s)
{
    int ext_code, ext_len, i, gce_flags, gce_transparent_index;

    /* There must be at least 2 bytes:
     * 1 for extension label and 1 for extension length. */
    if (s->bytestream_end < s->bytestream + 2)
        return AVERROR_INVALIDDATA;

    ext_code = bytestream_get_byte(&s->bytestream);
    ext_len = bytestream_get_byte(&s->bytestream);

    av_dlog(s->avctx, "ext_code=0x%x len=%d\n", ext_code, ext_len);

    switch(ext_code) {
    case GIF_GCE_EXT_LABEL:
        if (ext_len != 4)
            goto discard_ext;

        /* We need at least 5 bytes more: 4 is for extension body
         * and 1 for next block size. */
        if (s->bytestream_end < s->bytestream + 5)
            return AVERROR_INVALIDDATA;

        s->transparent_color_index = -1;
        gce_flags = bytestream_get_byte(&s->bytestream);
        bytestream_get_le16(&s->bytestream);    // delay during which the frame is shown
        gce_transparent_index = bytestream_get_byte(&s->bytestream);
        if (gce_flags & 0x01)
            s->transparent_color_index = gce_transparent_index;
        else
            s->transparent_color_index = -1;
        s->gce_disposal = (gce_flags >> 2) & 0x7;

        av_dlog(s->avctx, "gce_flags=%x tcolor=%d disposal=%d\n",
               gce_flags,
               s->transparent_color_index, s->gce_disposal);

        if (s->gce_disposal > 3) {
            s->gce_disposal = GCE_DISPOSAL_NONE;
            av_dlog(s->avctx, "invalid value in gce_disposal (%d). Using default value of 0.\n", ext_len);
        }

        ext_len = bytestream_get_byte(&s->bytestream);
        break;
    }

    /* NOTE: many extension blocks can come after */
 discard_ext:
    while (ext_len != 0) {
        /* There must be at least ext_len bytes and 1 for next block size byte. */
        if (s->bytestream_end < s->bytestream + ext_len + 1)
            return AVERROR_INVALIDDATA;

        for (i = 0; i < ext_len; i++)
            bytestream_get_byte(&s->bytestream);
        ext_len = bytestream_get_byte(&s->bytestream);

        av_dlog(s->avctx, "ext_len1=%d\n", ext_len);
    }
    return 0;
}

static int decode(AVCodecContext *avctx, void *data, int *data_size,
                  AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size       = avpkt->size;

    const uint8_t *buf_end;
    uint8_t       segment_type;
    int           segment_length;

#ifdef DEBUG_PACKET_CONTENTS
    int i;

    av_log(avctx, AV_LOG_INFO, "PGS sub packet:\n");

    for (i = 0; i < buf_size; i++) {
        av_log(avctx, AV_LOG_INFO, "%02x ", buf[i]);
        if (i % 16 == 15)
            av_log(avctx, AV_LOG_INFO, "\n");
    }

    if (i & 15)
        av_log(avctx, AV_LOG_INFO, "\n");
#endif

    *data_size = 0;

    /* Ensure that we have received at a least a segment code and segment length */
    if (buf_size < 3)
        return -1;

    buf_end = buf + buf_size;

    /* Step through buffer to identify segments */
    while (buf < buf_end) {
        segment_type   = bytestream_get_byte(&buf);
        segment_length = bytestream_get_be16(&buf);

        av_dlog(avctx, "Segment Length %d, Segment Type %x\n", segment_length, segment_type);

        if (segment_type != DISPLAY_SEGMENT && segment_length > buf_end - buf)
            break;

        switch (segment_type) {
        case PALETTE_SEGMENT:
            parse_palette_segment(avctx, buf, segment_length);
            break;
        case PICTURE_SEGMENT:
            parse_picture_segment(avctx, buf, segment_length);
            break;
        case PRESENTATION_SEGMENT:
            parse_presentation_segment(avctx, buf, segment_length);
            break;
        case WINDOW_SEGMENT:
            /*
             * Window Segment Structure (No new information provided):
             *     2 bytes: Unkown,
             *     2 bytes: X position of subtitle,
             *     2 bytes: Y position of subtitle,
             *     2 bytes: Width of subtitle,
             *     2 bytes: Height of subtitle.
             */
            break;
        case DISPLAY_SEGMENT:
            *data_size = display_end_segment(avctx, data, buf, segment_length);
            break;
        default:
            av_log(avctx, AV_LOG_ERROR, "Unknown subtitle segment type 0x%x, length %d\n",
                   segment_type, segment_length);
            break;
        }

        buf += segment_length;
    }

    return buf_size;
}

/**
 * Parse the picture segment packet.
 *
 * The picture segment contains details on the sequence id,
 * width, height and Run Length Encoded (RLE) bitmap data.
 *
 * @param avctx contains the current codec context
 * @param buf pointer to the packet to process
 * @param buf_size size of packet to process
 * @todo TODO: Enable support for RLE data over multiple packets
 */
static int parse_picture_segment(AVCodecContext *avctx,
                                  const uint8_t *buf, int buf_size)
{
    PGSSubContext *ctx = avctx->priv_data;

    uint8_t sequence_desc;
    unsigned int rle_bitmap_len, width, height;

    if (buf_size <= 4)
        return -1;
    buf_size -= 4;

    /* skip 3 unknown bytes: Object ID (2 bytes), Version Number */
    buf += 3;

    /* Read the Sequence Description to determine if start of RLE data or appended to previous RLE */
    sequence_desc = bytestream_get_byte(&buf);

    if (!(sequence_desc & 0x80)) {
        /* Additional RLE data */
        if (buf_size > ctx->picture.rle_remaining_len)
            return -1;

        memcpy(ctx->picture.rle + ctx->picture.rle_data_len, buf, buf_size);
        ctx->picture.rle_data_len += buf_size;
        ctx->picture.rle_remaining_len -= buf_size;

        return 0;
    }

    if (buf_size <= 7)
        return -1;
    buf_size -= 7;

    /* Decode rle bitmap length, stored size includes width/height data */
    rle_bitmap_len = bytestream_get_be24(&buf) - 2*2;

    /* Get bitmap dimensions from data */
    width  = bytestream_get_be16(&buf);
    height = bytestream_get_be16(&buf);

    /* Make sure the bitmap is not too large */
    if (avctx->width < width || avctx->height < height) {
        av_log(avctx, AV_LOG_ERROR, "Bitmap dimensions larger then video.\n");
        return -1;
    }

    ctx->picture.w = width;
    ctx->picture.h = height;

    av_fast_malloc(&ctx->picture.rle, &ctx->picture.rle_buffer_size, rle_bitmap_len);

    if (!ctx->picture.rle)
        return -1;

    memcpy(ctx->picture.rle, buf, buf_size);
    ctx->picture.rle_data_len = buf_size;
    ctx->picture.rle_remaining_len = rle_bitmap_len - buf_size;

    return 0;
}

static int flac_read_header(AVFormatContext *s)
{
    int ret, metadata_last=0, metadata_type, metadata_size, found_streaminfo=0;
    uint8_t header[4];
    uint8_t *buffer=NULL,*tmp=NULL;
    AVStream *st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);
    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
    st->codec->codec_id = AV_CODEC_ID_FLAC;
    st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
    /* the parameters will be extracted from the compressed bitstream */

    /* if fLaC marker is not found, assume there is no header */
    if (avio_rl32(s->pb) != MKTAG('f','L','a','C')) {
        avio_seek(s->pb, -4, SEEK_CUR);
        return 0;
    }

    /* process metadata blocks */
    while (!url_feof(s->pb) && !metadata_last) {
        avio_read(s->pb, header, 4);
        avpriv_flac_parse_block_header(header, &metadata_last, &metadata_type,
                                   &metadata_size);
        switch (metadata_type) {
        /* allocate and read metadata block for supported types */
        case FLAC_METADATA_TYPE_STREAMINFO:
        case FLAC_METADATA_TYPE_CUESHEET:
        case FLAC_METADATA_TYPE_PICTURE:
        case FLAC_METADATA_TYPE_VORBIS_COMMENT:
            buffer = av_mallocz(metadata_size + FF_INPUT_BUFFER_PADDING_SIZE);
            if (!buffer) {
                return AVERROR(ENOMEM);
            }
            if (avio_read(s->pb, buffer, metadata_size) != metadata_size) {
                RETURN_ERROR(AVERROR(EIO));
            }
            break;
        /* skip metadata block for unsupported types */
        default:
            ret = avio_skip(s->pb, metadata_size);
            if (ret < 0)
                return ret;
        }

        if (metadata_type == FLAC_METADATA_TYPE_STREAMINFO) {
            FLACStreaminfo si;
            /* STREAMINFO can only occur once */
            if (found_streaminfo) {
                RETURN_ERROR(AVERROR_INVALIDDATA);
            }
            if (metadata_size != FLAC_STREAMINFO_SIZE) {
                RETURN_ERROR(AVERROR_INVALIDDATA);
            }
            found_streaminfo = 1;
            st->codec->extradata      = av_malloc(metadata_size + 8 + FF_INPUT_BUFFER_PADDING_SIZE);
            if (!st->codec->extradata) {
              RETURN_ERROR(AVERROR(ENOMEM));
            }
            st->codec->extradata_size = metadata_size + 8;
            AV_WL32(st->codec->extradata, MKTAG('f','L','a','C'));
            memcpy(st->codec->extradata + 4, header, 4);
            memcpy(st->codec->extradata + 8, buffer, metadata_size);
            av_freep(&buffer);

            /* get codec params from STREAMINFO header */
            avpriv_flac_parse_streaminfo(st->codec, &si, st->codec->extradata + 8);

            /* set time base and duration */
            if (si.samplerate > 0) {
                avpriv_set_pts_info(st, 64, 1, si.samplerate);
                if (si.samples > 0)
                    st->duration = si.samples;
            }
        } else if (metadata_type == FLAC_METADATA_TYPE_CUESHEET) {
            uint8_t isrc[13];
            uint64_t start;
            const uint8_t *offset;
            int i, chapters, track, ti;
            if (metadata_size < 431)
                RETURN_ERROR(AVERROR_INVALIDDATA);
            offset = buffer + 395;
            chapters = bytestream_get_byte(&offset) - 1;
            if (chapters <= 0)
                RETURN_ERROR(AVERROR_INVALIDDATA);
            for (i = 0; i < chapters; i++) {
                if (offset + 36 - buffer > metadata_size)
                    RETURN_ERROR(AVERROR_INVALIDDATA);
                start = bytestream_get_be64(&offset);
                track = bytestream_get_byte(&offset);
                bytestream_get_buffer(&offset, isrc, 12);
                isrc[12] = 0;
                offset += 14;
                ti = bytestream_get_byte(&offset);
                if (ti <= 0) RETURN_ERROR(AVERROR_INVALIDDATA);
                offset += ti * 12;
                avpriv_new_chapter(s, track, st->time_base, start, AV_NOPTS_VALUE, isrc);
            }
            av_freep(&buffer);
        } else if (metadata_type == FLAC_METADATA_TYPE_PICTURE) {
//.........这里部分代码省略.........