libavcodec/ljpegenc.c:89: error: Uninitialized Value
  The value read from top[_] was never initialized.

libavcodec/ljpegenc.c:89:21: 
87.                     int pred, diff;
88. 
89.                     PREDICT(pred, topleft[i], top[i], left[i], modified_predictor);
                        ^
90. 
91.                     topleft[i]= top[i];

static int encode_picture_lossless(AVCodecContext *avctx, unsigned char *buf, int buf_size, void *data){
    MpegEncContext * const s = avctx->priv_data;
    MJpegContext * const m = s->mjpeg_ctx;
    AVFrame *pict = data;
    const int width= s->width;
    const int height= s->height;
    AVFrame * const p= (AVFrame*)&s->current_picture;
    const int predictor= avctx->prediction_method+1;
    init_put_bits(&s->pb, buf, buf_size);
    *p = *pict;
    p->pict_type= FF_I_TYPE;
    p->key_frame= 1;
    ff_mjpeg_encode_picture_header(s);
    s->header_bits= put_bits_count(&s->pb);
    if(avctx->pix_fmt == PIX_FMT_RGB32){
        int x, y, i;
        const int linesize= p->linesize[0];
        uint16_t (*buffer)[4]= (void *) s->rd_scratchpad;
        int left[3], top[3], topleft[3];
        for(i=0; i<3; i++){
            buffer[0][i]= 1 << (9 - 1);
        }
        for(y = 0; y < height; y++) {
            const int modified_predictor= y ? predictor : 1;
            uint8_t *ptr = p->data[0] + (linesize * y);
            if(s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < width*3*4){
                av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
                return -1;
            }
            for(i=0; i<3; i++){
                top[i]= left[i]= topleft[i]= buffer[0][i];
            }
            for(x = 0; x < width; x++) {
                buffer[x][1] = ptr[4*x+0] - ptr[4*x+1] + 0x100;
                buffer[x][2] = ptr[4*x+2] - ptr[4*x+1] + 0x100;
                buffer[x][0] = (ptr[4*x+0] + 2*ptr[4*x+1] + ptr[4*x+2])>>2;
                for(i=0;i<3;i++) {
                    int pred, diff;
                    PREDICT(pred, topleft[i], top[i], left[i], modified_predictor);
                    topleft[i]= top[i];
                    top[i]= buffer[x+1][i];
                    left[i]= buffer[x][i];
                    diff= ((left[i] - pred + 0x100)&0x1FF) - 0x100;
                    if(i==0)
                        ff_mjpeg_encode_dc(s, diff, m->huff_size_dc_luminance, m->huff_code_dc_luminance);
                    else
                        ff_mjpeg_encode_dc(s, diff, m->huff_size_dc_chrominance, m->huff_code_dc_chrominance);
                }
            }
        }
    }else{
        int mb_x, mb_y, i;
        const int mb_width  = (width  + s->mjpeg_hsample[0] - 1) / s->mjpeg_hsample[0];
        const int mb_height = (height + s->mjpeg_vsample[0] - 1) / s->mjpeg_vsample[0];
        for(mb_y = 0; mb_y < mb_height; mb_y++) {
            if(s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < mb_width * 4 * 3 * s->mjpeg_hsample[0] * s->mjpeg_vsample[0]){
                av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
                return -1;
            }
            for(mb_x = 0; mb_x < mb_width; mb_x++) {
                if(mb_x==0 || mb_y==0){
                    for(i=0;i<3;i++) {
                        uint8_t *ptr;
                        int x, y, h, v, linesize;
                        h = s->mjpeg_hsample[i];
                        v = s->mjpeg_vsample[i];
                        linesize= p->linesize[i];
                        for(y=0; y<v; y++){
                            for(x=0; x<h; x++){
                                int pred;
                                ptr = p->data[i] + (linesize * (v * mb_y + y)) + (h * mb_x + x);
                                if(y==0 && mb_y==0){
                                    if(x==0 && mb_x==0){
                                        pred= 128;
                                    }else{
                                        pred= ptr[-1];
                                    }
                                }else{
                                    if(x==0 && mb_x==0){
                                        pred= ptr[-linesize];
                                    }else{
                                        PREDICT(pred, ptr[-linesize-1], ptr[-linesize], ptr[-1], predictor);
                                    }
                                }
                                if(i==0)
                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_luminance, m->huff_code_dc_luminance);
                                else
                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_chrominance, m->huff_code_dc_chrominance);
                            }
                        }
                    }
                }else{
                    for(i=0;i<3;i++) {
                        uint8_t *ptr;
                        int x, y, h, v, linesize;
                        h = s->mjpeg_hsample[i];
                        v = s->mjpeg_vsample[i];
                        linesize= p->linesize[i];
                        for(y=0; y<v; y++){
                            for(x=0; x<h; x++){
                                int pred;
                                ptr = p->data[i] + (linesize * (v * mb_y + y)) + (h * mb_x + x);
                                PREDICT(pred, ptr[-linesize-1], ptr[-linesize], ptr[-1], predictor);
                                if(i==0)
                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_luminance, m->huff_code_dc_luminance);
                                else
                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_chrominance, m->huff_code_dc_chrominance);
                            }
                        }
                    }
                }
            }
        }
    }
    emms_c();
    ff_mjpeg_encode_picture_trailer(s);
    s->picture_number++;
    flush_put_bits(&s->pb);
    return pbBufPtr(&s->pb) - s->pb.buf;
}
['static int encode_picture_lossless(AVCodecContext *avctx, unsigned char *buf, int buf_size, void *data){\n    MpegEncContext * const s = avctx->priv_data;\n    MJpegContext * const m = s->mjpeg_ctx;\n    AVFrame *pict = data;\n    const int width= s->width;\n    const int height= s->height;\n    AVFrame * const p= (AVFrame*)&s->current_picture;\n    const int predictor= avctx->prediction_method+1;\n    init_put_bits(&s->pb, buf, buf_size);\n    *p = *pict;\n    p->pict_type= FF_I_TYPE;\n    p->key_frame= 1;\n    ff_mjpeg_encode_picture_header(s);\n    s->header_bits= put_bits_count(&s->pb);\n    if(avctx->pix_fmt == PIX_FMT_RGB32){\n        int x, y, i;\n        const int linesize= p->linesize[0];\n        uint16_t (*buffer)[4]= (void *) s->rd_scratchpad;\n        int left[3], top[3], topleft[3];\n        for(i=0; i<3; i++){\n            buffer[0][i]= 1 << (9 - 1);\n        }\n        for(y = 0; y < height; y++) {\n            const int modified_predictor= y ? predictor : 1;\n            uint8_t *ptr = p->data[0] + (linesize * y);\n            if(s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < width*3*4){\n                av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\\n");\n                return -1;\n            }\n            for(i=0; i<3; i++){\n                top[i]= left[i]= topleft[i]= buffer[0][i];\n            }\n            for(x = 0; x < width; x++) {\n                buffer[x][1] = ptr[4*x+0] - ptr[4*x+1] + 0x100;\n                buffer[x][2] = ptr[4*x+2] - ptr[4*x+1] + 0x100;\n                buffer[x][0] = (ptr[4*x+0] + 2*ptr[4*x+1] + ptr[4*x+2])>>2;\n                for(i=0;i<3;i++) {\n                    int pred, diff;\n                    PREDICT(pred, topleft[i], top[i], left[i], modified_predictor);\n                    topleft[i]= top[i];\n                    top[i]= buffer[x+1][i];\n                    left[i]= buffer[x][i];\n                    diff= ((left[i] - pred + 0x100)&0x1FF) - 0x100;\n                    if(i==0)\n                        ff_mjpeg_encode_dc(s, diff, m->huff_size_dc_luminance, m->huff_code_dc_luminance);\n                    else\n                        ff_mjpeg_encode_dc(s, diff, m->huff_size_dc_chrominance, m->huff_code_dc_chrominance);\n                }\n            }\n        }\n    }else{\n        int mb_x, mb_y, i;\n        const int mb_width  = (width  + s->mjpeg_hsample[0] - 1) / s->mjpeg_hsample[0];\n        const int mb_height = (height + s->mjpeg_vsample[0] - 1) / s->mjpeg_vsample[0];\n        for(mb_y = 0; mb_y < mb_height; mb_y++) {\n            if(s->pb.buf_end - s->pb.buf - (put_bits_count(&s->pb)>>3) < mb_width * 4 * 3 * s->mjpeg_hsample[0] * s->mjpeg_vsample[0]){\n                av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\\n");\n                return -1;\n            }\n            for(mb_x = 0; mb_x < mb_width; mb_x++) {\n                if(mb_x==0 || mb_y==0){\n                    for(i=0;i<3;i++) {\n                        uint8_t *ptr;\n                        int x, y, h, v, linesize;\n                        h = s->mjpeg_hsample[i];\n                        v = s->mjpeg_vsample[i];\n                        linesize= p->linesize[i];\n                        for(y=0; y<v; y++){\n                            for(x=0; x<h; x++){\n                                int pred;\n                                ptr = p->data[i] + (linesize * (v * mb_y + y)) + (h * mb_x + x);\n                                if(y==0 && mb_y==0){\n                                    if(x==0 && mb_x==0){\n                                        pred= 128;\n                                    }else{\n                                        pred= ptr[-1];\n                                    }\n                                }else{\n                                    if(x==0 && mb_x==0){\n                                        pred= ptr[-linesize];\n                                    }else{\n                                        PREDICT(pred, ptr[-linesize-1], ptr[-linesize], ptr[-1], predictor);\n                                    }\n                                }\n                                if(i==0)\n                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_luminance, m->huff_code_dc_luminance);\n                                else\n                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_chrominance, m->huff_code_dc_chrominance);\n                            }\n                        }\n                    }\n                }else{\n                    for(i=0;i<3;i++) {\n                        uint8_t *ptr;\n                        int x, y, h, v, linesize;\n                        h = s->mjpeg_hsample[i];\n                        v = s->mjpeg_vsample[i];\n                        linesize= p->linesize[i];\n                        for(y=0; y<v; y++){\n                            for(x=0; x<h; x++){\n                                int pred;\n                                ptr = p->data[i] + (linesize * (v * mb_y + y)) + (h * mb_x + x);\n                                PREDICT(pred, ptr[-linesize-1], ptr[-linesize], ptr[-1], predictor);\n                                if(i==0)\n                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_luminance, m->huff_code_dc_luminance);\n                                else\n                                    ff_mjpeg_encode_dc(s, (int8_t)(*ptr - pred), m->huff_size_dc_chrominance, m->huff_code_dc_chrominance);\n                            }\n                        }\n                    }\n                }\n            }\n        }\n    }\n    emms_c();\n    ff_mjpeg_encode_picture_trailer(s);\n    s->picture_number++;\n    flush_put_bits(&s->pb);\n    return pbBufPtr(&s->pb) - s->pb.buf;\n}']