static int pnm_decode_frame(AVCodecContext *avctx, void *data,

                            int *data_size, AVPacket *avpkt)

{

    const uint8_t *buf   = avpkt->data;

    int buf_size         = avpkt->size;

    PNMContext * const s = avctx->priv_data;

    AVFrame *picture     = data;

    AVFrame * const p    = (AVFrame*)&s->picture;

    int i, j, n, linesize, h, upgrade = 0;

    unsigned char *ptr;

    int components, sample_len;



    s->bytestream_start =

    s->bytestream       = buf;

    s->bytestream_end   = buf + buf_size;



    if (ff_pnm_decode_header(avctx, s) < 0)

        return -1;



    if (p->data[0])

        avctx->release_buffer(avctx, p);



    p->reference = 0;

    if (avctx->get_buffer(avctx, p) < 0) {

        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");

        return -1;

    }

    p->pict_type = AV_PICTURE_TYPE_I;

    p->key_frame = 1;



    switch (avctx->pix_fmt) {

    default:

        return -1;

    case PIX_FMT_RGB48BE:

        n = avctx->width * 6;

        components=3;

        sample_len=16;

        goto do_read;

    case PIX_FMT_RGB24:

        n = avctx->width * 3;

        components=3;

        sample_len=8;

        goto do_read;

    case PIX_FMT_GRAY8:

        n = avctx->width;

        components=1;

        sample_len=8;

        if (s->maxval < 255)

            upgrade = 1;

        goto do_read;

    case PIX_FMT_GRAY16BE:

    case PIX_FMT_GRAY16LE:

        n = avctx->width * 2;

        components=1;

        sample_len=16;

        if (s->maxval < 65535)

            upgrade = 2;

        goto do_read;

    case PIX_FMT_MONOWHITE:

    case PIX_FMT_MONOBLACK:

        n = (avctx->width + 7) >> 3;

        components=1;

        sample_len=1;

    do_read:

        ptr      = p->data[0];

        linesize = p->linesize[0];

        if (s->bytestream + n * avctx->height > s->bytestream_end)

            return -1;

        if(s->type < 4){

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

                PutBitContext pb;

                init_put_bits(&pb, ptr, linesize);

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

                    unsigned int c=0;

                    int v=0;

                    while(s->bytestream < s->bytestream_end && (*s->bytestream < '0' || *s->bytestream > '9' ))

                        s->bytestream++;

                    if(s->bytestream >= s->bytestream_end)

                        return -1;

                    do{

                        v= 10*v + c;

                        c= (*s->bytestream++) - '0';

                    }while(c <= 9);

                    put_bits(&pb, sample_len, (((1<<sample_len)-1)*v + (s->maxval>>1))/s->maxval);

                }

                flush_put_bits(&pb);

                ptr+= linesize;

            }

        }else{

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

            if (!upgrade)

                memcpy(ptr, s->bytestream, n);

            else if (upgrade == 1) {

                unsigned int j, f = (255 * 128 + s->maxval / 2) / s->maxval;

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

                    ptr[j] = (s->bytestream[j] * f + 64) >> 7;

            } else if (upgrade == 2) {

                unsigned int j, v, f = (65535 * 32768 + s->maxval / 2) / s->maxval;

                for (j = 0; j < n / 2; j++) {

                    v = av_be2ne16(((uint16_t *)s->bytestream)[j]);

                    ((uint16_t *)ptr)[j] = (v * f + 16384) >> 15;

                }

            }

            s->bytestream += n;

            ptr           += linesize;

        }

        }

        break;

    case PIX_FMT_YUV420P:

        {

            unsigned char *ptr1, *ptr2;



            n        = avctx->width;

            ptr      = p->data[0];

            linesize = p->linesize[0];

            if (s->bytestream + n * avctx->height * 3 / 2 > s->bytestream_end)

                return -1;

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

                memcpy(ptr, s->bytestream, n);

                s->bytestream += n;

                ptr           += linesize;

            }

            ptr1 = p->data[1];

            ptr2 = p->data[2];

            n >>= 1;

            h = avctx->height >> 1;

            for (i = 0; i < h; i++) {

                memcpy(ptr1, s->bytestream, n);

                s->bytestream += n;

                memcpy(ptr2, s->bytestream, n);

                s->bytestream += n;

                ptr1 += p->linesize[1];

                ptr2 += p->linesize[2];

            }

        }

        break;

    case PIX_FMT_RGB32:

        ptr      = p->data[0];

        linesize = p->linesize[0];

        if (s->bytestream + avctx->width * avctx->height * 4 > s->bytestream_end)

            return -1;

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

            int j, r, g, b, a;



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

                r = *s->bytestream++;

                g = *s->bytestream++;

                b = *s->bytestream++;

                a = *s->bytestream++;

                ((uint32_t *)ptr)[j] = (a << 24) | (r << 16) | (g << 8) | b;

            }

            ptr += linesize;

        }

        break;

    }

    *picture   = *(AVFrame*)&s->picture;

    *data_size = sizeof(AVPicture);



    return s->bytestream - s->bytestream_start;

}
