/*
  * 4XM codec
  * Copyright (c) 2003 Michael Niedermayer
  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * FFmpeg is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  */

 /**

  * @file libavcodec/4xm.c

  * 4XM codec.
  */

 #include "libavutil/intreadwrite.h"

 #include "avcodec.h"
 #include "dsputil.h"

 #include "bitstream.h"

 #include "bytestream.h"

 
 //#undef NDEBUG
 //#include <assert.h>
 
 #define BLOCK_TYPE_VLC_BITS 5
 #define ACDC_VLC_BITS 9
 
 #define CFRAME_BUFFER_COUNT 100
 

 static const uint8_t block_type_tab[2][4][8][2]={
  {

   {   //{8,4,2}x{8,4,2}
     { 0,1}, { 2,2}, { 6,3}, {14,4}, {30,5}, {31,5}, { 0,0}
   },{ //{8,4}x1
     { 0,1}, { 0,0}, { 2,2}, { 6,3}, {14,4}, {15,4}, { 0,0}
   },{ //1x{8,4}
     { 0,1}, { 2,2}, { 0,0}, { 6,3}, {14,4}, {15,4}, { 0,0}
   },{ //1x2, 2x1
     { 0,1}, { 0,0}, { 0,0}, { 2,2}, { 6,3}, {14,4}, {15,4}
   }

  },{
   {  //{8,4,2}x{8,4,2}
     { 1,2}, { 4,3}, { 5,3}, {0,2}, {6,3}, {7,3}, {0,0}
   },{//{8,4}x1
     { 1,2}, { 0,0}, { 2,2}, {0,2}, {6,3}, {7,3}, {0,0}
   },{//1x{8,4}
     { 1,2}, { 2,2}, { 0,0}, {0,2}, {6,3}, {7,3}, {0,0}
   },{//1x2, 2x1
     { 1,2}, { 0,0}, { 0,0}, {0,2}, {2,2}, {6,3}, {7,3}
   }
  }

 };
 
 static const uint8_t size2index[4][4]={
   {-1, 3, 1, 1},
   { 3, 0, 0, 0},
   { 2, 0, 0, 0},
   { 2, 0, 0, 0},
 };
 
 static const int8_t mv[256][2]={
 {  0,  0},{  0, -1},{ -1,  0},{  1,  0},{  0,  1},{ -1, -1},{  1, -1},{ -1,  1},
 {  1,  1},{  0, -2},{ -2,  0},{  2,  0},{  0,  2},{ -1, -2},{  1, -2},{ -2, -1},
 {  2, -1},{ -2,  1},{  2,  1},{ -1,  2},{  1,  2},{ -2, -2},{  2, -2},{ -2,  2},
 {  2,  2},{  0, -3},{ -3,  0},{  3,  0},{  0,  3},{ -1, -3},{  1, -3},{ -3, -1},
 {  3, -1},{ -3,  1},{  3,  1},{ -1,  3},{  1,  3},{ -2, -3},{  2, -3},{ -3, -2},
 {  3, -2},{ -3,  2},{  3,  2},{ -2,  3},{  2,  3},{  0, -4},{ -4,  0},{  4,  0},
 {  0,  4},{ -1, -4},{  1, -4},{ -4, -1},{  4, -1},{  4,  1},{ -1,  4},{  1,  4},
 { -3, -3},{ -3,  3},{  3,  3},{ -2, -4},{ -4, -2},{  4, -2},{ -4,  2},{ -2,  4},
 {  2,  4},{ -3, -4},{  3, -4},{  4, -3},{ -5,  0},{ -4,  3},{ -3,  4},{  3,  4},
 { -1, -5},{ -5, -1},{ -5,  1},{ -1,  5},{ -2, -5},{  2, -5},{  5, -2},{  5,  2},
 { -4, -4},{ -4,  4},{ -3, -5},{ -5, -3},{ -5,  3},{  3,  5},{ -6,  0},{  0,  6},
 { -6, -1},{ -6,  1},{  1,  6},{  2, -6},{ -6,  2},{  2,  6},{ -5, -4},{  5,  4},
 {  4,  5},{ -6, -3},{  6,  3},{ -7,  0},{ -1, -7},{  5, -5},{ -7,  1},{ -1,  7},
 {  4, -6},{  6,  4},{ -2, -7},{ -7,  2},{ -3, -7},{  7, -3},{  3,  7},{  6, -5},
 {  0, -8},{ -1, -8},{ -7, -4},{ -8,  1},{  4,  7},{  2, -8},{ -2,  8},{  6,  6},
 { -8,  3},{  5, -7},{ -5,  7},{  8, -4},{  0, -9},{ -9, -1},{  1,  9},{  7, -6},
 { -7,  6},{ -5, -8},{ -5,  8},{ -9,  3},{  9, -4},{  7, -7},{  8, -6},{  6,  8},
 { 10,  1},{-10,  2},{  9, -5},{ 10, -3},{ -8, -7},{-10, -4},{  6, -9},{-11,  0},
 { 11,  1},{-11, -2},{ -2, 11},{  7, -9},{ -7,  9},{ 10,  6},{ -4, 11},{  8, -9},
 {  8,  9},{  5, 11},{  7,-10},{ 12, -3},{ 11,  6},{ -9, -9},{  8, 10},{  5, 12},
 {-11,  7},{ 13,  2},{  6,-12},{ 10,  9},{-11,  8},{ -7, 12},{  0, 14},{ 14, -2},
 { -9, 11},{ -6, 13},{-14, -4},{ -5,-14},{  5, 14},{-15, -1},{-14, -6},{  3,-15},
 { 11,-11},{ -7, 14},{ -5, 15},{  8,-14},{ 15,  6},{  3, 16},{  7,-15},{-16,  5},
 {  0, 17},{-16, -6},{-10, 14},{-16,  7},{ 12, 13},{-16,  8},{-17,  6},{-18,  3},
 { -7, 17},{ 15, 11},{ 16, 10},{  2,-19},{  3,-19},{-11,-16},{-18,  8},{-19, -6},
 {  2,-20},{-17,-11},{-10,-18},{  8, 19},{-21, -1},{-20,  7},{ -4, 21},{ 21,  5},
 { 15, 16},{  2,-22},{-10,-20},{-22,  5},{ 20,-11},{ -7,-22},{-12, 20},{ 23, -5},
 { 13,-20},{ 24, -2},{-15, 19},{-11, 22},{ 16, 19},{ 23,-10},{-18,-18},{ -9,-24},
 { 24,-10},{ -3, 26},{-23, 13},{-18,-20},{ 17, 21},{ -4, 27},{ 27,  6},{  1,-28},
 {-11, 26},{-17,-23},{  7, 28},{ 11,-27},{ 29,  5},{-23,-19},{-28,-11},{-21, 22},
 {-30,  7},{-17, 26},{-27, 16},{ 13, 29},{ 19,-26},{ 10,-31},{-14,-30},{ 20,-27},
 {-29, 18},{-16,-31},{-28,-22},{ 21,-30},{-25, 28},{ 26,-29},{ 25,-32},{-32,-32}
 };
 
 // this is simply the scaled down elementwise product of the standard jpeg quantizer table and the AAN premul table
 static const uint8_t dequant_table[64]={
  16, 15, 13, 19, 24, 31, 28, 17,
  17, 23, 25, 31, 36, 63, 45, 21,
  18, 24, 27, 37, 52, 59, 49, 20,
  16, 28, 34, 40, 60, 80, 51, 20,
  18, 31, 48, 66, 68, 86, 56, 21,
  19, 38, 56, 59, 64, 64, 48, 20,
  27, 48, 55, 55, 56, 51, 35, 15,
  20, 35, 34, 32, 31, 22, 15,  8,
 };
 

 static VLC block_type_vlc[2][4];

 
 
 typedef struct CFrameBuffer{

     unsigned int allocated_size;
     unsigned int size;

     int id;
     uint8_t *data;
 }CFrameBuffer;
 
 typedef struct FourXContext{
     AVCodecContext *avctx;
     DSPContext dsp;
     AVFrame current_picture, last_picture;
     GetBitContext pre_gb;          ///< ac/dc prefix
     GetBitContext gb;

     const uint8_t *bytestream;

     const uint8_t *bytestream_end;

     const uint16_t *wordstream;

     const uint16_t *wordstream_end;

     int mv[256];
     VLC pre_vlc;
     int last_dc;

     DECLARE_ALIGNED_8(DCTELEM, block[6][64]);

     uint8_t *bitstream_buffer;

     unsigned int bitstream_buffer_size;

     int version;

     CFrameBuffer cfrm[CFRAME_BUFFER_COUNT];
 } FourXContext;
 
 
 #define FIX_1_082392200  70936
 #define FIX_1_414213562  92682
 #define FIX_1_847759065 121095
 #define FIX_2_613125930 171254
 
 #define MULTIPLY(var,const)  (((var)*(const)) >> 16)
 
 static void idct(DCTELEM block[64]){
     int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
     int tmp10, tmp11, tmp12, tmp13;
     int z5, z10, z11, z12, z13;
     int i;
     int temp[64];

     for(i=0; i<8; i++){
         tmp10 = block[8*0 + i] + block[8*4 + i];
         tmp11 = block[8*0 + i] - block[8*4 + i];
 
         tmp13 =          block[8*2 + i] + block[8*6 + i];
         tmp12 = MULTIPLY(block[8*2 + i] - block[8*6 + i], FIX_1_414213562) - tmp13;
 
         tmp0 = tmp10 + tmp13;
         tmp3 = tmp10 - tmp13;
         tmp1 = tmp11 + tmp12;
         tmp2 = tmp11 - tmp12;

         z13 = block[8*5 + i] + block[8*3 + i];
         z10 = block[8*5 + i] - block[8*3 + i];
         z11 = block[8*1 + i] + block[8*7 + i];
         z12 = block[8*1 + i] - block[8*7 + i];
 
         tmp7  =          z11 + z13;
         tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562);
 
         z5    = MULTIPLY(z10 + z12, FIX_1_847759065);
         tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5;
         tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5;
 
         tmp6 = tmp12 - tmp7;
         tmp5 = tmp11 - tmp6;
         tmp4 = tmp10 + tmp5;
 
         temp[8*0 + i] = tmp0 + tmp7;
         temp[8*7 + i] = tmp0 - tmp7;
         temp[8*1 + i] = tmp1 + tmp6;
         temp[8*6 + i] = tmp1 - tmp6;
         temp[8*2 + i] = tmp2 + tmp5;
         temp[8*5 + i] = tmp2 - tmp5;
         temp[8*4 + i] = tmp3 + tmp4;
         temp[8*3 + i] = tmp3 - tmp4;
     }

     for(i=0; i<8*8; i+=8){
         tmp10 = temp[0 + i] + temp[4 + i];
         tmp11 = temp[0 + i] - temp[4 + i];
 
         tmp13 = temp[2 + i] + temp[6 + i];
         tmp12 = MULTIPLY(temp[2 + i] - temp[6 + i], FIX_1_414213562) - tmp13;
 
         tmp0 = tmp10 + tmp13;
         tmp3 = tmp10 - tmp13;
         tmp1 = tmp11 + tmp12;
         tmp2 = tmp11 - tmp12;
 
         z13 = temp[5 + i] + temp[3 + i];
         z10 = temp[5 + i] - temp[3 + i];
         z11 = temp[1 + i] + temp[7 + i];
         z12 = temp[1 + i] - temp[7 + i];
 
         tmp7 = z11 + z13;
         tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562);
 
         z5 = MULTIPLY(z10 + z12, FIX_1_847759065);
         tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5;
         tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5;
 
         tmp6 = tmp12 - tmp7;
         tmp5 = tmp11 - tmp6;
         tmp4 = tmp10 + tmp5;
 
         block[0 + i] = (tmp0 + tmp7)>>6;
         block[7 + i] = (tmp0 - tmp7)>>6;
         block[1 + i] = (tmp1 + tmp6)>>6;
         block[6 + i] = (tmp1 - tmp6)>>6;
         block[2 + i] = (tmp2 + tmp5)>>6;
         block[5 + i] = (tmp2 - tmp5)>>6;
         block[4 + i] = (tmp3 + tmp4)>>6;
         block[3 + i] = (tmp3 - tmp4)>>6;
     }
 }
 

 static av_cold void init_vlcs(FourXContext *f){

     int i;
 

     for(i=0; i<8; i++){
         init_vlc(&block_type_vlc[0][i], BLOCK_TYPE_VLC_BITS, 7,
                  &block_type_tab[0][i][0][1], 2, 1,
                  &block_type_tab[0][i][0][0], 2, 1, 1);

     }
 }
 
 static void init_mv(FourXContext *f){
     int i;
 
     for(i=0; i<256; i++){

         if(f->version>1)

             f->mv[i] = mv[i][0]   + mv[i][1]  *f->current_picture.linesize[0]/2;
         else
             f->mv[i] = (i&15) - 8 + ((i>>4)-8)*f->current_picture.linesize[0]/2;

     }
 }
 
 static inline void mcdc(uint16_t *dst, uint16_t *src, int log2w, int h, int stride, int scale, int dc){
    int i;
    dc*= 0x10001;
 
    switch(log2w){
    case 0:
         for(i=0; i<h; i++){
             dst[0] = scale*src[0] + dc;
             if(scale) src += stride;
             dst += stride;
         }
         break;
     case 1:
         for(i=0; i<h; i++){
             ((uint32_t*)dst)[0] = scale*((uint32_t*)src)[0] + dc;
             if(scale) src += stride;
             dst += stride;
         }
         break;
     case 2:
         for(i=0; i<h; i++){
             ((uint32_t*)dst)[0] = scale*((uint32_t*)src)[0] + dc;
             ((uint32_t*)dst)[1] = scale*((uint32_t*)src)[1] + dc;
             if(scale) src += stride;
             dst += stride;
         }
         break;
     case 3:
         for(i=0; i<h; i++){
             ((uint32_t*)dst)[0] = scale*((uint32_t*)src)[0] + dc;
             ((uint32_t*)dst)[1] = scale*((uint32_t*)src)[1] + dc;
             ((uint32_t*)dst)[2] = scale*((uint32_t*)src)[2] + dc;
             ((uint32_t*)dst)[3] = scale*((uint32_t*)src)[3] + dc;
             if(scale) src += stride;
             dst += stride;
         }
         break;
     default: assert(0);
     }
 }
 
 static void decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src, int log2w, int log2h, int stride){
     const int index= size2index[log2h][log2w];
     const int h= 1<<log2h;

     int code= get_vlc2(&f->gb, block_type_vlc[1-(f->version>1)][index].table, BLOCK_TYPE_VLC_BITS, 1);

     uint16_t *start= (uint16_t*)f->last_picture.data[0];

     uint16_t *end= start + stride*(f->avctx->height-h+1) - (1<<log2w);

     assert(code>=0 && code<=6);
 
     if(code == 0){

         if (f->bytestream_end - f->bytestream < 1)
             return;

         src += f->mv[ *f->bytestream++ ];

         if(start > src || src > end){
             av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
             return;
         }

         mcdc(dst, src, log2w, h, stride, 1, 0);
     }else if(code == 1){
         log2h--;
         decode_p_block(f, dst                  , src                  , log2w, log2h, stride);
         decode_p_block(f, dst + (stride<<log2h), src + (stride<<log2h), log2w, log2h, stride);
     }else if(code == 2){
         log2w--;
         decode_p_block(f, dst             , src             , log2w, log2h, stride);
         decode_p_block(f, dst + (1<<log2w), src + (1<<log2w), log2w, log2h, stride);

     }else if(code == 3 && f->version<2){

         mcdc(dst, src, log2w, h, stride, 1, 0);

     }else if(code == 4){

         if (f->bytestream_end - f->bytestream < 1)
             return;

         src += f->mv[ *f->bytestream++ ];

         if(start > src || src > end){
             av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
             return;
         }

         if (f->wordstream_end - f->wordstream < 1)
             return;

         mcdc(dst, src, log2w, h, stride, 1, le2me_16(*f->wordstream++));
     }else if(code == 5){

         if (f->wordstream_end - f->wordstream < 1)
             return;

         mcdc(dst, src, log2w, h, stride, 0, le2me_16(*f->wordstream++));
     }else if(code == 6){

         if (f->wordstream_end - f->wordstream < 2)
             return;

         if(log2w){
             dst[0] = le2me_16(*f->wordstream++);
             dst[1] = le2me_16(*f->wordstream++);
         }else{
             dst[0     ] = le2me_16(*f->wordstream++);
             dst[stride] = le2me_16(*f->wordstream++);
         }
     }
 }
 

 static int decode_p_frame(FourXContext *f, const uint8_t *buf, int length){

     int x, y;
     const int width= f->avctx->width;
     const int height= f->avctx->height;
     uint16_t *src= (uint16_t*)f->last_picture.data[0];
     uint16_t *dst= (uint16_t*)f->current_picture.data[0];
     const int stride= f->current_picture.linesize[0]>>1;

     unsigned int bitstream_size, bytestream_size, wordstream_size, extra;
 

     if(f->version>1){

         extra=20;

         if (length < extra)
             return -1;

         bitstream_size= AV_RL32(buf+8);
         wordstream_size= AV_RL32(buf+12);
         bytestream_size= AV_RL32(buf+16);

     }else{
         extra=0;
         bitstream_size = AV_RL16(buf-4);
         wordstream_size= AV_RL16(buf-2);
         bytestream_size= FFMAX(length - bitstream_size - wordstream_size, 0);
     }

     if (bitstream_size > length ||
         bytestream_size > length - bitstream_size ||
         wordstream_size > length - bytestream_size - bitstream_size ||
         extra > length - bytestream_size - bitstream_size - wordstream_size){

         av_log(f->avctx, AV_LOG_ERROR, "lengths %d %d %d %d\n", bitstream_size, bytestream_size, wordstream_size,

         bitstream_size+ bytestream_size+ wordstream_size - length);

         return -1;
     }

     f->bitstream_buffer= av_fast_realloc(f->bitstream_buffer, &f->bitstream_buffer_size, bitstream_size + FF_INPUT_BUFFER_PADDING_SIZE);

     f->dsp.bswap_buf((uint32_t*)f->bitstream_buffer, (const uint32_t*)(buf + extra), bitstream_size/4);

     init_get_bits(&f->gb, f->bitstream_buffer, 8*bitstream_size);
 

     f->wordstream= (const uint16_t*)(buf + extra + bitstream_size);

     f->wordstream_end= f->wordstream + wordstream_size/2;

     f->bytestream= buf + extra + bitstream_size + wordstream_size;

     f->bytestream_end = f->bytestream + bytestream_size;

     init_mv(f);

     for(y=0; y<height; y+=8){
         for(x=0; x<width; x+=8){
             decode_p_block(f, dst + x, src + x, 3, 3, stride);
         }

         src += 8*stride;
         dst += 8*stride;

     }

     if(   bitstream_size != (get_bits_count(&f->gb)+31)/32*4

        || (((const char*)f->wordstream - (const char*)buf + 2)&~2) != extra + bitstream_size + wordstream_size
        || (((const char*)f->bytestream - (const char*)buf + 3)&~3) != extra + bitstream_size + wordstream_size + bytestream_size)

         av_log(f->avctx, AV_LOG_ERROR, " %d %td %td bytes left\n",
             bitstream_size - (get_bits_count(&f->gb)+31)/32*4,

             -(((const char*)f->bytestream - (const char*)buf + 3)&~3) + (extra + bitstream_size + wordstream_size + bytestream_size),
             -(((const char*)f->wordstream - (const char*)buf + 2)&~2) + (extra + bitstream_size + wordstream_size)

         );

     return 0;
 }
 
 /**
  * decode block and dequantize.

  * Note this is almost identical to MJPEG.

  */
 static int decode_i_block(FourXContext *f, DCTELEM *block){
     int code, i, j, level, val;
 
     /* DC coef */
     val = get_vlc2(&f->pre_gb, f->pre_vlc.table, ACDC_VLC_BITS, 3);
     if (val>>4){

         av_log(f->avctx, AV_LOG_ERROR, "error dc run != 0\n");

     }
 
     if(val)
         val = get_xbits(&f->gb, val);
 
     val = val * dequant_table[0] + f->last_dc;
     f->last_dc =
     block[0] = val;
     /* AC coefs */
     i = 1;
     for(;;) {
         code = get_vlc2(&f->pre_gb, f->pre_vlc.table, ACDC_VLC_BITS, 3);

         /* EOB */
         if (code == 0)
             break;
         if (code == 0xf0) {
             i += 16;
         } else {
             level = get_xbits(&f->gb, code & 0xf);
             i += code >> 4;
             if (i >= 64) {

                 av_log(f->avctx, AV_LOG_ERROR, "run %d oveflow\n", i);

                 return 0;
             }
 
             j= ff_zigzag_direct[i];
             block[j] = level * dequant_table[j];
             i++;
             if (i >= 64)
                 break;
         }
     }
 
     return 0;
 }
 
 static inline void idct_put(FourXContext *f, int x, int y){
     DCTELEM (*block)[64]= f->block;
     int stride= f->current_picture.linesize[0]>>1;
     int i;
     uint16_t *dst = ((uint16_t*)f->current_picture.data[0]) + y * stride + x;

     for(i=0; i<4; i++){
         block[i][0] += 0x80*8*8;
         idct(block[i]);
     }

     if(!(f->avctx->flags&CODEC_FLAG_GRAY)){
         for(i=4; i<6; i++) idct(block[i]);
     }

 /* Note transform is:
 y= ( 1b + 4g + 2r)/14
 cb=( 3b - 2g - 1r)/14
 cr=(-1b - 4g + 5r)/14

 */

     for(y=0; y<8; y++){
         for(x=0; x<8; x++){
             DCTELEM *temp= block[(x>>2) + 2*(y>>2)] + 2*(x&3) + 2*8*(y&3); //FIXME optimize

             int cb= block[4][x + 8*y];
             int cr= block[5][x + 8*y];

             int cg= (cb + cr)>>1;
             int y;

             cb+=cb;

             y = temp[0];

             dst[0       ]= ((y+cb)>>3) + (((y-cg)&0xFC)<<3) + (((y+cr)&0xF8)<<8);

             y = temp[1];

             dst[1       ]= ((y+cb)>>3) + (((y-cg)&0xFC)<<3) + (((y+cr)&0xF8)<<8);

             y = temp[8];

             dst[  stride]= ((y+cb)>>3) + (((y-cg)&0xFC)<<3) + (((y+cr)&0xF8)<<8);

             y = temp[9];

             dst[1+stride]= ((y+cb)>>3) + (((y-cg)&0xFC)<<3) + (((y+cr)&0xF8)<<8);

             dst += 2;
         }
         dst += 2*stride - 2*8;
     }
 }
 
 static int decode_i_mb(FourXContext *f){
     int i;

     f->dsp.clear_blocks(f->block[0]);

     for(i=0; i<6; i++){
         if(decode_i_block(f, f->block[i]) < 0)
             return -1;
     }

     return 0;
 }
 

 static const uint8_t *read_huffman_tables(FourXContext *f, const uint8_t * const buf, int buf_size){

     int frequency[512];
     uint8_t flag[512];
     int up[512];
     uint8_t len_tab[257];
     int bits_tab[257];
     int start, end;

     const uint8_t *ptr= buf;

     const uint8_t *ptr_end = buf + buf_size;

     int j;

     memset(frequency, 0, sizeof(frequency));
     memset(up, -1, sizeof(up));
 
     start= *ptr++;
     end= *ptr++;
     for(;;){
         int i;

         if (start <= end && ptr_end - ptr < end - start + 1 + 1)
             return NULL;

         for(i=start; i<=end; i++){
             frequency[i]= *ptr++;
         }
         start= *ptr++;
         if(start==0) break;

         end= *ptr++;
     }
     frequency[256]=1;
 

     while((ptr - buf)&3) ptr++; // 4byte align

 
     for(j=257; j<512; j++){

         int min_freq[2]= {256*256, 256*256};
         int smallest[2]= {0, 0};

         int i;
         for(i=0; i<j; i++){
             if(frequency[i] == 0) continue;

             if(frequency[i] < min_freq[1]){
                 if(frequency[i] < min_freq[0]){
                     min_freq[1]= min_freq[0]; smallest[1]= smallest[0];
                     min_freq[0]= frequency[i];smallest[0]= i;
                 }else{
                     min_freq[1]= frequency[i];smallest[1]= i;
                 }

             }
         }

         if(min_freq[1] == 256*256) break;

         frequency[j]= min_freq[0] + min_freq[1];

         flag[ smallest[0] ]= 0;
         flag[ smallest[1] ]= 1;

         up[ smallest[0] ]=

         up[ smallest[1] ]= j;
         frequency[ smallest[0] ]= frequency[ smallest[1] ]= 0;
     }
 
     for(j=0; j<257; j++){
         int node;
         int len=0;
         int bits=0;
 
         for(node= j; up[node] != -1; node= up[node]){
             bits += flag[node]<<len;
             len++;

             if(len > 31) av_log(f->avctx, AV_LOG_ERROR, "vlc length overflow\n"); //can this happen at all ?

         }

         bits_tab[j]= bits;
         len_tab[j]= len;
     }

 
     init_vlc(&f->pre_vlc, ACDC_VLC_BITS, 257,

              len_tab , 1, 1,

              bits_tab, 4, 4, 0);

     return ptr;
 }
 

 static int mix(int c0, int c1){
     int blue = 2*(c0&0x001F) + (c1&0x001F);
     int green= (2*(c0&0x03E0) + (c1&0x03E0))>>5;
     int red  = 2*(c0>>10) + (c1>>10);
     return red/3*1024 + green/3*32 + blue/3;
 }
 

 static int decode_i2_frame(FourXContext *f, const uint8_t *buf, int length){

     int x, y, x2, y2;
     const int width= f->avctx->width;
     const int height= f->avctx->height;
     uint16_t *dst= (uint16_t*)f->current_picture.data[0];
     const int stride= f->current_picture.linesize[0]>>1;

     const uint8_t *buf_end = buf + length;

 
     for(y=0; y<height; y+=16){
         for(x=0; x<width; x+=16){
             unsigned int color[4], bits;

             if (buf_end - buf < 8)
                 return -1;

             memset(color, 0, sizeof(color));
 //warning following is purely guessed ...

             color[0]= bytestream_get_le16(&buf);
             color[1]= bytestream_get_le16(&buf);

 
             if(color[0]&0x8000) av_log(NULL, AV_LOG_ERROR, "unk bit 1\n");
             if(color[1]&0x8000) av_log(NULL, AV_LOG_ERROR, "unk bit 2\n");
 
             color[2]= mix(color[0], color[1]);
             color[3]= mix(color[1], color[0]);
 

             bits= bytestream_get_le32(&buf);

             for(y2=0; y2<16; y2++){
                 for(x2=0; x2<16; x2++){
                     int index= 2*(x2>>2) + 8*(y2>>2);
                     dst[y2*stride+x2]= color[(bits>>index)&3];
                 }
             }
             dst+=16;
         }
         dst += 16*stride - width;
     }
 
     return 0;
 }
 

 static int decode_i_frame(FourXContext *f, const uint8_t *buf, int length){

     int x, y;
     const int width= f->avctx->width;
     const int height= f->avctx->height;
     uint16_t *dst= (uint16_t*)f->current_picture.data[0];
     const int stride= f->current_picture.linesize[0]>>1;

     const unsigned int bitstream_size= AV_RL32(buf);

     unsigned int prestream_size;
     const uint8_t *prestream;
 
     if (bitstream_size > (1<<26) || length < bitstream_size + 12)
         return -1;
     prestream_size = 4*AV_RL32(buf + bitstream_size + 4);
     prestream = buf + bitstream_size + 12;

     if (prestream_size > (1<<26) ||
         prestream_size != length - (bitstream_size + 12)){

         av_log(f->avctx, AV_LOG_ERROR, "size mismatch %d %d %d\n", prestream_size, bitstream_size, length);

         return -1;
     }

     prestream= read_huffman_tables(f, prestream, buf + length - prestream);
     if (!prestream)
         return -1;

 
     init_get_bits(&f->gb, buf + 4, 8*bitstream_size);
 
     prestream_size= length + buf - prestream;

     f->bitstream_buffer= av_fast_realloc(f->bitstream_buffer, &f->bitstream_buffer_size, prestream_size + FF_INPUT_BUFFER_PADDING_SIZE);

     f->dsp.bswap_buf((uint32_t*)f->bitstream_buffer, (const uint32_t*)prestream, prestream_size/4);

     init_get_bits(&f->pre_gb, f->bitstream_buffer, 8*prestream_size);
 
     f->last_dc= 0*128*8*8;

     for(y=0; y<height; y+=16){
         for(x=0; x<width; x+=16){
             if(decode_i_mb(f) < 0)
                 return -1;
 
             idct_put(f, x, y);
         }

         dst += 16*stride;

     }
 
     if(get_vlc2(&f->pre_gb, f->pre_vlc.table, ACDC_VLC_BITS, 3) != 256)

         av_log(f->avctx, AV_LOG_ERROR, "end mismatch\n");

     return 0;
 }
 

 static int decode_frame(AVCodecContext *avctx,

                         void *data, int *data_size,

                         const uint8_t *buf, int buf_size)

 {
     FourXContext * const f = avctx->priv_data;
     AVFrame *picture = data;
     AVFrame *p, temp;
     int i, frame_4cc, frame_size;
 

     if (buf_size < 12)
         return AVERROR_INVALIDDATA;

     frame_4cc= AV_RL32(buf);
     if(buf_size != AV_RL32(buf+4)+8 || buf_size < 20){
         av_log(f->avctx, AV_LOG_ERROR, "size mismatch %d %d\n", buf_size, AV_RL32(buf+4));

     }
 

     if(frame_4cc == AV_RL32("cfrm")){

         int free_index=-1;
         const int data_size= buf_size - 20;

         const int id= AV_RL32(buf+12);
         const int whole_size= AV_RL32(buf+16);

         CFrameBuffer *cfrm;
 

         if (data_size < 0 || whole_size < 0)
             return AVERROR_INVALIDDATA;
 

         for(i=0; i<CFRAME_BUFFER_COUNT; i++){
             if(f->cfrm[i].id && f->cfrm[i].id < avctx->frame_number)

                 av_log(f->avctx, AV_LOG_ERROR, "lost c frame %d\n", f->cfrm[i].id);

         }

         for(i=0; i<CFRAME_BUFFER_COUNT; i++){
             if(f->cfrm[i].id   == id) break;
             if(f->cfrm[i].size == 0 ) free_index= i;
         }
 
         if(i>=CFRAME_BUFFER_COUNT){
             i= free_index;
             f->cfrm[i].id= id;
         }
         cfrm= &f->cfrm[i];

         if (data_size > UINT_MAX -  cfrm->size - FF_INPUT_BUFFER_PADDING_SIZE)
             return AVERROR_INVALIDDATA;

         cfrm->data= av_fast_realloc(cfrm->data, &cfrm->allocated_size, cfrm->size + data_size + FF_INPUT_BUFFER_PADDING_SIZE);

         if(!cfrm->data){ //explicit check needed as memcpy below might not catch a NULL
             av_log(f->avctx, AV_LOG_ERROR, "realloc falure");
             return -1;
         }

         memcpy(cfrm->data + cfrm->size, buf+20, data_size);
         cfrm->size += data_size;

         if(cfrm->size >= whole_size){
             buf= cfrm->data;
             frame_size= cfrm->size;

             if(id != avctx->frame_number){

                 av_log(f->avctx, AV_LOG_ERROR, "cframe id mismatch %d %d\n", id, avctx->frame_number);

             }

             cfrm->size= cfrm->id= 0;

             frame_4cc= AV_RL32("pfrm");

         }else
             return buf_size;
     }else{
         buf= buf + 12;
         frame_size= buf_size - 12;

     }

 
     temp= f->current_picture;
     f->current_picture= f->last_picture;
     f->last_picture= temp;
 
     p= &f->current_picture;
     avctx->coded_frame= p;
 
     avctx->flags |= CODEC_FLAG_EMU_EDGE; // alternatively we would have to use our own buffer management
 
     if(p->data[0])
         avctx->release_buffer(avctx, p);
 
     p->reference= 1;
     if(avctx->get_buffer(avctx, p) < 0){

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

         return -1;
     }
 

     if(frame_4cc == AV_RL32("ifr2")){

         p->pict_type= FF_I_TYPE;

         if(decode_i2_frame(f, buf-4, frame_size) < 0)
             return -1;

     }else if(frame_4cc == AV_RL32("ifrm")){

         p->pict_type= FF_I_TYPE;

         if(decode_i_frame(f, buf, frame_size) < 0)
             return -1;

     }else if(frame_4cc == AV_RL32("pfrm") || frame_4cc == AV_RL32("pfr2")){

         p->pict_type= FF_P_TYPE;

         if(decode_p_frame(f, buf, frame_size) < 0)
             return -1;

     }else if(frame_4cc == AV_RL32("snd_")){

         av_log(avctx, AV_LOG_ERROR, "ignoring snd_ chunk length:%d\n", buf_size);

     }else{

         av_log(avctx, AV_LOG_ERROR, "ignoring unknown chunk length:%d\n", buf_size);

     }
 

     p->key_frame= p->pict_type == FF_I_TYPE;

 
     *picture= *p;
     *data_size = sizeof(AVPicture);
 
     emms_c();

     return buf_size;
 }
 
 

 static av_cold void common_init(AVCodecContext *avctx){

     FourXContext * const f = avctx->priv_data;
 
     dsputil_init(&f->dsp, avctx);
 
     f->avctx= avctx;
 }
 

 static av_cold int decode_init(AVCodecContext *avctx){

     FourXContext * const f = avctx->priv_data;

     if(avctx->extradata_size != 4 || !avctx->extradata) {
         av_log(avctx, AV_LOG_ERROR, "extradata wrong or missing\n");
         return 1;
     }
 

     f->version= AV_RL32(avctx->extradata)>>16;

     common_init(avctx);
     init_vlcs(f);
 

     if(f->version>2) avctx->pix_fmt= PIX_FMT_RGB565;
     else             avctx->pix_fmt= PIX_FMT_RGB555;

 
     return 0;
 }
 
 

 static av_cold int decode_end(AVCodecContext *avctx){

     FourXContext * const f = avctx->priv_data;
     int i;
 
     av_freep(&f->bitstream_buffer);
     f->bitstream_buffer_size=0;
     for(i=0; i<CFRAME_BUFFER_COUNT; i++){
         av_freep(&f->cfrm[i].data);
         f->cfrm[i].allocated_size= 0;
     }
     free_vlc(&f->pre_vlc);

     return 0;
 }
 
 AVCodec fourxm_decoder = {
     "4xm",
     CODEC_TYPE_VIDEO,
     CODEC_ID_4XM,
     sizeof(FourXContext),
     decode_init,
     NULL,
     decode_end,
     decode_frame,
     /*CODEC_CAP_DR1,*/

     .long_name = NULL_IF_CONFIG_SMALL("4X Movie"),

 };