static int bmp_decode_frame(AVCodecContext *avctx,

                            void *data, int *got_frame,

                            AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size       = avpkt->size;

    AVFrame *p         = data;

    unsigned int fsize, hsize;

    int width, height;

    unsigned int depth;

    BiCompression comp;

    unsigned int ihsize;

    int i, j, n, linesize, ret;

    uint32_t rgb[3] = {0};

    uint32_t alpha = 0;

    uint8_t *ptr;

    int dsize;

    const uint8_t *buf0 = buf;

    GetByteContext gb;



    if (buf_size < 14) {

        av_log(avctx, AV_LOG_ERROR, "buf size too small (%d)\n", buf_size);

        return AVERROR_INVALIDDATA;

    }



    if (bytestream_get_byte(&buf) != 'B' ||

        bytestream_get_byte(&buf) != 'M') {

        av_log(avctx, AV_LOG_ERROR, "bad magic number\n");

        return AVERROR_INVALIDDATA;

    }



    fsize = bytestream_get_le32(&buf);

    if (buf_size < fsize) {

        av_log(avctx, AV_LOG_ERROR, "not enough data (%d < %u), trying to decode anyway\n",

               buf_size, fsize);

        fsize = buf_size;

    }



    buf += 2; /* reserved1 */

    buf += 2; /* reserved2 */



    hsize  = bytestream_get_le32(&buf); /* header size */

    ihsize = bytestream_get_le32(&buf); /* more header size */

    if (ihsize + 14LL > hsize) {

        av_log(avctx, AV_LOG_ERROR, "invalid header size %u\n", hsize);

        return AVERROR_INVALIDDATA;

    }



    /* sometimes file size is set to some headers size, set a real size in that case */

    if (fsize == 14 || fsize == ihsize + 14)

        fsize = buf_size - 2;



    if (fsize <= hsize) {

        av_log(avctx, AV_LOG_ERROR,

               "Declared file size is less than header size (%u < %u)\n",

               fsize, hsize);

        return AVERROR_INVALIDDATA;

    }



    switch (ihsize) {

    case  40: // windib

    case  56: // windib v3

    case  64: // OS/2 v2

    case 108: // windib v4

    case 124: // windib v5

        width  = bytestream_get_le32(&buf);

        height = bytestream_get_le32(&buf);

        break;

    case  12: // OS/2 v1

        width  = bytestream_get_le16(&buf);

        height = bytestream_get_le16(&buf);

        break;

    default:

        avpriv_report_missing_feature(avctx, "Information header size %u",

                                      ihsize);

        return AVERROR_PATCHWELCOME;

    }



    /* planes */

    if (bytestream_get_le16(&buf) != 1) {

        av_log(avctx, AV_LOG_ERROR, "invalid BMP header\n");

        return AVERROR_INVALIDDATA;

    }



    depth = bytestream_get_le16(&buf);



    if (ihsize >= 40)

        comp = bytestream_get_le32(&buf);

    else

        comp = BMP_RGB;



    if (comp != BMP_RGB && comp != BMP_BITFIELDS && comp != BMP_RLE4 &&

        comp != BMP_RLE8) {

        av_log(avctx, AV_LOG_ERROR, "BMP coding %d not supported\n", comp);

        return AVERROR_INVALIDDATA;

    }



    if (comp == BMP_BITFIELDS) {

        buf += 20;

        rgb[0] = bytestream_get_le32(&buf);

        rgb[1] = bytestream_get_le32(&buf);

        rgb[2] = bytestream_get_le32(&buf);

        if (ihsize > 40)

        alpha = bytestream_get_le32(&buf);

    }



    avctx->width  = width;

    avctx->height = height > 0 ? height : -(unsigned)height;



    avctx->pix_fmt = AV_PIX_FMT_NONE;



    switch (depth) {

    case 32:

        if (comp == BMP_BITFIELDS) {

            if (rgb[0] == 0xFF000000 && rgb[1] == 0x00FF0000 && rgb[2] == 0x0000FF00)

                avctx->pix_fmt = alpha ? AV_PIX_FMT_ABGR : AV_PIX_FMT_0BGR;

            else if (rgb[0] == 0x00FF0000 && rgb[1] == 0x0000FF00 && rgb[2] == 0x000000FF)

                avctx->pix_fmt = alpha ? AV_PIX_FMT_BGRA : AV_PIX_FMT_BGR0;

            else if (rgb[0] == 0x0000FF00 && rgb[1] == 0x00FF0000 && rgb[2] == 0xFF000000)

                avctx->pix_fmt = alpha ? AV_PIX_FMT_ARGB : AV_PIX_FMT_0RGB;

            else if (rgb[0] == 0x000000FF && rgb[1] == 0x0000FF00 && rgb[2] == 0x00FF0000)

                avctx->pix_fmt = alpha ? AV_PIX_FMT_RGBA : AV_PIX_FMT_RGB0;

            else {

                av_log(avctx, AV_LOG_ERROR, "Unknown bitfields "

                       "%0"PRIX32" %0"PRIX32" %0"PRIX32"\n", rgb[0], rgb[1], rgb[2]);

                return AVERROR(EINVAL);

            }

        } else {

            avctx->pix_fmt = AV_PIX_FMT_BGRA;

        }

        break;

    case 24:

        avctx->pix_fmt = AV_PIX_FMT_BGR24;

        break;

    case 16:

        if (comp == BMP_RGB)

            avctx->pix_fmt = AV_PIX_FMT_RGB555;

        else if (comp == BMP_BITFIELDS) {

            if (rgb[0] == 0xF800 && rgb[1] == 0x07E0 && rgb[2] == 0x001F)

               avctx->pix_fmt = AV_PIX_FMT_RGB565;

            else if (rgb[0] == 0x7C00 && rgb[1] == 0x03E0 && rgb[2] == 0x001F)

               avctx->pix_fmt = AV_PIX_FMT_RGB555;

            else if (rgb[0] == 0x0F00 && rgb[1] == 0x00F0 && rgb[2] == 0x000F)

               avctx->pix_fmt = AV_PIX_FMT_RGB444;

            else {

               av_log(avctx, AV_LOG_ERROR,

                      "Unknown bitfields %0"PRIX32" %0"PRIX32" %0"PRIX32"\n",

                      rgb[0], rgb[1], rgb[2]);

               return AVERROR(EINVAL);

            }

        }

        break;

    case 8:

        if (hsize - ihsize - 14 > 0)

            avctx->pix_fmt = AV_PIX_FMT_PAL8;

        else

            avctx->pix_fmt = AV_PIX_FMT_GRAY8;

        break;

    case 1:

    case 4:

        if (hsize - ihsize - 14 > 0) {

            avctx->pix_fmt = AV_PIX_FMT_PAL8;

        } else {

            av_log(avctx, AV_LOG_ERROR, "Unknown palette for %u-colour BMP\n",

                   1 << depth);

            return AVERROR_INVALIDDATA;

        }

        break;

    default:

        av_log(avctx, AV_LOG_ERROR, "depth %u not supported\n", depth);

        return AVERROR_INVALIDDATA;

    }



    if (avctx->pix_fmt == AV_PIX_FMT_NONE) {

        av_log(avctx, AV_LOG_ERROR, "unsupported pixel format\n");

        return AVERROR_INVALIDDATA;

    }



    if ((ret = ff_get_buffer(avctx, p, 0)) < 0)

        return ret;

    p->pict_type = AV_PICTURE_TYPE_I;

    p->key_frame = 1;



    buf   = buf0 + hsize;

    dsize = buf_size - hsize;



    /* Line size in file multiple of 4 */

    n = ((avctx->width * depth + 31) / 8) & ~3;



    if (n * avctx->height > dsize && comp != BMP_RLE4 && comp != BMP_RLE8) {

        n = (avctx->width * depth + 7) / 8;

        if (n * avctx->height > dsize) {

            av_log(avctx, AV_LOG_ERROR, "not enough data (%d < %d)\n",

                   dsize, n * avctx->height);

            return AVERROR_INVALIDDATA;

        }

        av_log(avctx, AV_LOG_ERROR, "data size too small, assuming missing line alignment\n");

    }



    // RLE may skip decoding some picture areas, so blank picture before decoding

    if (comp == BMP_RLE4 || comp == BMP_RLE8)

        memset(p->data[0], 0, avctx->height * p->linesize[0]);



    if (height > 0) {

        ptr      = p->data[0] + (avctx->height - 1) * p->linesize[0];

        linesize = -p->linesize[0];

    } else {

        ptr      = p->data[0];

        linesize = p->linesize[0];

    }



    if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {

        int colors = 1 << depth;



        memset(p->data[1], 0, 1024);



        if (ihsize >= 36) {

            int t;

            buf = buf0 + 46;

            t   = bytestream_get_le32(&buf);

            if (t < 0 || t > (1 << depth)) {

                av_log(avctx, AV_LOG_ERROR,

                       "Incorrect number of colors - %X for bitdepth %u\n",

                       t, depth);

            } else if (t) {

                colors = t;

            }

        } else {

            colors = FFMIN(256, (hsize-ihsize-14) / 3);

        }

        buf = buf0 + 14 + ihsize; //palette location

        // OS/2 bitmap, 3 bytes per palette entry

        if ((hsize-ihsize-14) < (colors << 2)) {

            if ((hsize-ihsize-14) < colors * 3) {

                av_log(avctx, AV_LOG_ERROR, "palette doesn't fit in packet\n");

                return AVERROR_INVALIDDATA;

            }

            for (i = 0; i < colors; i++)

                ((uint32_t*)p->data[1])[i] = (0xFFU<<24) | bytestream_get_le24(&buf);

        } else {

            for (i = 0; i < colors; i++)

                ((uint32_t*)p->data[1])[i] = 0xFFU << 24 | bytestream_get_le32(&buf);

        }

        buf = buf0 + hsize;

    }

    if (comp == BMP_RLE4 || comp == BMP_RLE8) {

        if (comp == BMP_RLE8 && height < 0) {

            p->data[0]    +=  p->linesize[0] * (avctx->height - 1);

            p->linesize[0] = -p->linesize[0];

        }

        bytestream2_init(&gb, buf, dsize);

        ff_msrle_decode(avctx, p, depth, &gb);

        if (height < 0) {

            p->data[0]    +=  p->linesize[0] * (avctx->height - 1);

            p->linesize[0] = -p->linesize[0];

        }

    } else {

        switch (depth) {

        case 1:

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

                int j;

                for (j = 0; j < n; j++) {

                    ptr[j*8+0] =  buf[j] >> 7;

                    ptr[j*8+1] = (buf[j] >> 6) & 1;

                    ptr[j*8+2] = (buf[j] >> 5) & 1;

                    ptr[j*8+3] = (buf[j] >> 4) & 1;

                    ptr[j*8+4] = (buf[j] >> 3) & 1;

                    ptr[j*8+5] = (buf[j] >> 2) & 1;

                    ptr[j*8+6] = (buf[j] >> 1) & 1;

                    ptr[j*8+7] =  buf[j]       & 1;

                }

                buf += n;

                ptr += linesize;

            }

            break;

        case 8:

        case 24:

        case 32:

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

                memcpy(ptr, buf, n);

                buf += n;

                ptr += linesize;

            }

            break;

        case 4:

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

                int j;

                for (j = 0; j < n; j++) {

                    ptr[j*2+0] = (buf[j] >> 4) & 0xF;

                    ptr[j*2+1] = buf[j] & 0xF;

                }

                buf += n;

                ptr += linesize;

            }

            break;

        case 16:

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

                const uint16_t *src = (const uint16_t *) buf;

                uint16_t *dst       = (uint16_t *) ptr;



                for (j = 0; j < avctx->width; j++)

                    *dst++ = av_le2ne16(*src++);



                buf += n;

                ptr += linesize;

            }

            break;

        default:

            av_log(avctx, AV_LOG_ERROR, "BMP decoder is broken\n");

            return AVERROR_INVALIDDATA;

        }

    }

    if (avctx->pix_fmt == AV_PIX_FMT_BGRA) {

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

            int j;

            uint8_t *ptr = p->data[0] + p->linesize[0]*i + 3;

            for (j = 0; j < avctx->width; j++) {

                if (ptr[4*j])

                    break;

            }

            if (j < avctx->width)

                break;

        }

        if (i == avctx->height)

            avctx->pix_fmt = p->format = AV_PIX_FMT_BGR0;

    }



    *got_frame = 1;



    return buf_size;

}
