/*
  * Flash Screen Video encoder
  * Copyright (C) 2004 Alex Beregszaszi
  * Copyright (C) 2006 Benjamin Larsson
  *
  * 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
  */
 
 /* Encoding development sponsored by http://fh-campuswien.ac.at */
 
 /**

  * @file

  * Flash Screen Video encoder
  * @author Alex Beregszaszi
  * @author Benjamin Larsson
  */
 
 /* Bitstream description
  * The picture is divided into blocks that are zlib-compressed.
  *
  * The decoder is fed complete frames, the frameheader contains:
  * 4bits of block width
  * 12bits of frame width
  * 4bits of block height
  * 12bits of frame height
  *
  * Directly after the header are the compressed blocks. The blocks
  * have their compressed size represented with 16bits in the beginig.
  * If the size = 0 then the block is unchanged from the previous frame.
  * All blocks are decompressed until the buffer is consumed.
  *
  * Encoding ideas, a basic encoder would just use a fixed block size.
  * Block sizes can be multipels of 16, from 16 to 256. The blocks don't
  * have to be quadratic. A brute force search with a set of different
  * block sizes should give a better result than to just use a fixed size.
  */
 
 /* TODO:
  * Don't reencode the frame in brute force mode if the frame is a dupe. Speed up.
  * Make the difference check faster.
  */
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <zlib.h>
 
 #include "avcodec.h"

 #include "put_bits.h"

 #include "bytestream.h"
 
 
 typedef struct FlashSVContext {
     AVCodecContext *avctx;

     uint8_t        *previous_frame;
     AVFrame         frame;
     int             image_width, image_height;
     int             block_width, block_height;
     uint8_t        *tmpblock;
     uint8_t        *encbuffer;
     int             block_size;
     z_stream        zstream;
     int             last_key_frame;

 } FlashSVContext;
 

 static int copy_region_enc(uint8_t *sptr, uint8_t *dptr, int dx, int dy,
                            int h, int w, int stride, uint8_t *pfptr)
 {
     int i, j;

     uint8_t *nsptr;
     uint8_t *npfptr;
     int diff = 0;
 

     for (i = dx + h; i > dx; i--) {
         nsptr  = sptr  + (i * stride) + dy * 3;
         npfptr = pfptr + (i * stride) + dy * 3;
         for (j = 0; j < w * 3; j++) {
             diff    |= npfptr[j] ^ nsptr[j];
             dptr[j]  = nsptr[j];

         }

         dptr += w * 3;

     }
     if (diff)
         return 1;
     return 0;
 }
 

 static av_cold int flashsv_encode_init(AVCodecContext *avctx)

 {

     FlashSVContext *s = avctx->priv_data;

 
     s->avctx = avctx;
 
     if ((avctx->width > 4095) || (avctx->height > 4095)) {
         av_log(avctx, AV_LOG_ERROR, "Input dimensions too large, input must be max 4096x4096 !\n");

         return AVERROR_INVALIDDATA;

     }
 
     // Needed if zlib unused or init aborted before deflateInit
     memset(&(s->zstream), 0, sizeof(z_stream));
 

     s->last_key_frame = 0;

     s->image_width  = avctx->width;

     s->image_height = avctx->height;
 

     s->tmpblock  = av_mallocz(3 * 256 * 256);
     s->encbuffer = av_mallocz(s->image_width * s->image_height * 3);

 
     if (!s->tmpblock || !s->encbuffer) {
         av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");

         return AVERROR(ENOMEM);

     }
 
     return 0;
 }
 
 

 static int encode_bitstream(FlashSVContext *s, AVFrame *p, uint8_t *buf,
                             int buf_size, int block_width, int block_height,
                             uint8_t *previous_frame, int *I_frame)
 {

 
     PutBitContext pb;
     int h_blocks, v_blocks, h_part, v_part, i, j;
     int buf_pos, res;
     int pred_blocks = 0;
 

     init_put_bits(&pb, buf, buf_size * 8);

     put_bits(&pb,  4, (block_width / 16) - 1);

     put_bits(&pb, 12, s->image_width);

     put_bits(&pb,  4, (block_height / 16) - 1);

     put_bits(&pb, 12, s->image_height);
     flush_put_bits(&pb);

     buf_pos = 4;

     h_blocks = s->image_width  / block_width;
     h_part   = s->image_width  % block_width;

     v_blocks = s->image_height / block_height;

     v_part   = s->image_height % block_height;

 
     /* loop over all block columns */

     for (j = 0; j < v_blocks + (v_part ? 1 : 0); j++) {

         int hp = j * block_height; // horiz position in frame
         int hs = (j < v_blocks) ? block_height : v_part; // size of block

 
         /* loop over all block rows */

         for (i = 0; i < h_blocks + (h_part ? 1 : 0); i++) {
             int wp  = i * block_width; // vert position in frame
             int ws  = (i < h_blocks) ? block_width : h_part; // size of block
             int ret = Z_OK;

             uint8_t *ptr;
 

             ptr = buf + buf_pos;

             /* copy the block to the temp buffer before compression
              * (if it differs from the previous frame's block) */
             res = copy_region_enc(p->data[0], s->tmpblock,
                                   s->image_height - (hp + hs + 1),
                                   wp, hs, ws, p->linesize[0], previous_frame);

 
             if (res || *I_frame) {
                 unsigned long zsize;

                 zsize = 3 * block_width * block_height;
                 ret   = compress2(ptr + 2, &zsize, s->tmpblock, 3 * ws * hs, 9);

 
 
                 //ret = deflateReset(&(s->zstream));
                 if (ret != Z_OK)
                     av_log(s->avctx, AV_LOG_ERROR, "error while compressing block %dx%d\n", i, j);
 

                 bytestream_put_be16(&ptr, (unsigned int) zsize);
                 buf_pos += zsize + 2;

                 //av_log(avctx, AV_LOG_ERROR, "buf_pos = %d\n", buf_pos);
             } else {
                 pred_blocks++;

                 bytestream_put_be16(&ptr, 0);

                 buf_pos += 2;

             }
         }
     }
 
     if (pred_blocks)
         *I_frame = 0;
     else
         *I_frame = 1;
 
     return buf_pos;
 }
 
 

 static int flashsv_encode_frame(AVCodecContext *avctx, uint8_t *buf,
                                 int buf_size, void *data)

 {

     FlashSVContext * const s = avctx->priv_data;

     AVFrame *pict = data;
     AVFrame * const p = &s->frame;

     uint8_t *pfptr;

     int res;
     int I_frame = 0;
     int opt_w, opt_h;
 
     *p = *pict;
 

     /* First frame needs to be a keyframe */

     if (avctx->frame_number == 0) {

         s->previous_frame = av_mallocz(FFABS(p->linesize[0]) * s->image_height);

         if (!s->previous_frame) {
             av_log(avctx, AV_LOG_ERROR, "Memory allocation failed.\n");

             return AVERROR(ENOMEM);

         }
         I_frame = 1;
     }
 

     if (p->linesize[0] < 0)

         pfptr = s->previous_frame - ((s->image_height - 1) * p->linesize[0]);

     else
         pfptr = s->previous_frame;
 

     /* Check the placement of keyframes */
     if (avctx->gop_size > 0) {
         if (avctx->frame_number >= s->last_key_frame + avctx->gop_size) {
             I_frame = 1;
         }
     }
 

     opt_w = 4;
     opt_h = 4;

 
     if (buf_size < s->image_width*s->image_height*3) {
         //Conservative upper bound check for compressed data

         av_log(avctx, AV_LOG_ERROR, "buf_size %d <  %d\n",
                buf_size, s->image_width * s->image_height * 3);

         return -1;
     }
 

     res = encode_bitstream(s, p, buf, buf_size, opt_w * 16, opt_h * 16, pfptr, &I_frame);

     //save the current frame

     if (p->linesize[0] > 0)
         memcpy(s->previous_frame, p->data[0], s->image_height * p->linesize[0]);

     else

         memcpy(s->previous_frame, p->data[0] + p->linesize[0] * (s->image_height - 1),
                s->image_height * FFABS(p->linesize[0]));

 
     //mark the frame type so the muxer can mux it correctly
     if (I_frame) {

         p->pict_type = AV_PICTURE_TYPE_I;

         p->key_frame = 1;

         s->last_key_frame = avctx->frame_number;

         av_log(avctx, AV_LOG_DEBUG, "Inserting key frame at frame %d\n", avctx->frame_number);

     } else {

         p->pict_type = AV_PICTURE_TYPE_P;

         p->key_frame = 0;
     }
 
     avctx->coded_frame = p;
 
     return res;
 }
 

 static av_cold int flashsv_encode_end(AVCodecContext *avctx)

 {

     FlashSVContext *s = avctx->priv_data;

 
     deflateEnd(&(s->zstream));
 
     av_free(s->encbuffer);
     av_free(s->previous_frame);
     av_free(s->tmpblock);
 
     return 0;
 }
 

 AVCodec ff_flashsv_encoder = {

     .name           = "flashsv",
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = CODEC_ID_FLASHSV,
     .priv_data_size = sizeof(FlashSVContext),
     .init           = flashsv_encode_init,
     .encode         = flashsv_encode_frame,
     .close          = flashsv_encode_end,
     .pix_fmts       = (const enum PixelFormat[]){PIX_FMT_BGR24, PIX_FMT_NONE},
     .long_name      = NULL_IF_CONFIG_SMALL("Flash Screen Video"),

 };