/*
  * Go2Webinar decoder
  * Copyright (c) 2012 Konstantin Shishkov
  *

  * 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
  * Go2Webinar decoder
  */
 
 #include <zlib.h>
 
 #include "libavutil/intreadwrite.h"
 #include "avcodec.h"
 #include "bytestream.h"
 #include "dsputil.h"
 #include "get_bits.h"
 #include "internal.h"
 #include "mjpeg.h"
 
 enum ChunkType {
     FRAME_INFO = 0xC8,
     TILE_DATA,
     CURSOR_POS,
     CURSOR_SHAPE,
     CHUNK_CC,
     CHUNK_CD
 };
 
 enum Compression {
     COMPR_EPIC_J_B = 2,
     COMPR_KEMPF_J_B,
 };
 
 static const uint8_t luma_quant[64] = {
      8,  6,  5,  8, 12, 20, 26, 31,
      6,  6,  7, 10, 13, 29, 30, 28,
      7,  7,  8, 12, 20, 29, 35, 28,
      7,  9, 11, 15, 26, 44, 40, 31,
      9, 11, 19, 28, 34, 55, 52, 39,
     12, 18, 28, 32, 41, 52, 57, 46,
     25, 32, 39, 44, 52, 61, 60, 51,
     36, 46, 48, 49, 56, 50, 52, 50
 };
 
 static const uint8_t chroma_quant[64] = {
      9,  9, 12, 24, 50, 50, 50, 50,
      9, 11, 13, 33, 50, 50, 50, 50,
     12, 13, 28, 50, 50, 50, 50, 50,
     24, 33, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
     50, 50, 50, 50, 50, 50, 50, 50,
 };
 
 typedef struct JPGContext {
     DSPContext dsp;
     ScanTable  scantable;
 
     VLC        dc_vlc[2], ac_vlc[2];
     int        prev_dc[3];
     DECLARE_ALIGNED(16, int16_t, block)[6][64];
 
     uint8_t    *buf;
 } JPGContext;
 
 typedef struct G2MContext {
     JPGContext jc;
     int        version;
 
     int        compression;
     int        width, height, bpp;
     int        tile_width, tile_height;
     int        tiles_x, tiles_y, tile_x, tile_y;
 
     int        got_header;
 
     uint8_t    *framebuf;
     int        framebuf_stride, old_width, old_height;
 
     uint8_t    *synth_tile, *jpeg_tile;
     int        tile_stride, old_tile_w, old_tile_h;
 
     uint8_t    *kempf_buf, *kempf_flags;
 
     uint8_t    *cursor;
     int        cursor_stride;
     int        cursor_fmt;
     int        cursor_w, cursor_h, cursor_x, cursor_y;
     int        cursor_hot_x, cursor_hot_y;
 } G2MContext;
 
 static av_cold int build_vlc(VLC *vlc, const uint8_t *bits_table,
                              const uint8_t *val_table, int nb_codes,
                              int is_ac)
 {
     uint8_t  huff_size[256] = { 0 };
     uint16_t huff_code[256];
     uint16_t huff_sym[256];
     int i;
 
     ff_mjpeg_build_huffman_codes(huff_size, huff_code, bits_table, val_table);
 
     for (i = 0; i < 256; i++)
         huff_sym[i] = i + 16 * is_ac;
 
     if (is_ac)
         huff_sym[0] = 16 * 256;
 
     return ff_init_vlc_sparse(vlc, 9, nb_codes, huff_size, 1, 1,
                               huff_code, 2, 2, huff_sym, 2, 2, 0);
 }
 
 static av_cold int jpg_init(AVCodecContext *avctx, JPGContext *c)
 {
     int ret;
 
     ret = build_vlc(&c->dc_vlc[0], avpriv_mjpeg_bits_dc_luminance,
                     avpriv_mjpeg_val_dc, 12, 0);
     if (ret)
         return ret;
     ret = build_vlc(&c->dc_vlc[1], avpriv_mjpeg_bits_dc_chrominance,
                     avpriv_mjpeg_val_dc, 12, 0);
     if (ret)
         return ret;
     ret = build_vlc(&c->ac_vlc[0], avpriv_mjpeg_bits_ac_luminance,
                     avpriv_mjpeg_val_ac_luminance, 251, 1);
     if (ret)
         return ret;
     ret = build_vlc(&c->ac_vlc[1], avpriv_mjpeg_bits_ac_chrominance,
                     avpriv_mjpeg_val_ac_chrominance, 251, 1);
     if (ret)
         return ret;
 
     ff_dsputil_init(&c->dsp, avctx);
     ff_init_scantable(c->dsp.idct_permutation, &c->scantable,
                       ff_zigzag_direct);
 
     return 0;
 }
 
 static av_cold void jpg_free_context(JPGContext *ctx)
 {
     int i;
 
     for (i = 0; i < 2; i++) {
         ff_free_vlc(&ctx->dc_vlc[i]);
         ff_free_vlc(&ctx->ac_vlc[i]);
     }
 
     av_freep(&ctx->buf);
 }
 
 static void jpg_unescape(const uint8_t *src, int src_size,
                          uint8_t *dst, int *dst_size)
 {
     const uint8_t *src_end = src + src_size;
     uint8_t *dst_start = dst;
 
     while (src < src_end) {
         uint8_t x = *src++;
 
         *dst++ = x;
 
         if (x == 0xFF && !*src)
             src++;
     }
     *dst_size = dst - dst_start;
 }
 
 static int jpg_decode_block(JPGContext *c, GetBitContext *gb,
                             int plane, int16_t *block)
 {
     int dc, val, pos;
     const int is_chroma = !!plane;
     const uint8_t *qmat = is_chroma ? chroma_quant : luma_quant;
 
     c->dsp.clear_block(block);
     dc = get_vlc2(gb, c->dc_vlc[is_chroma].table, 9, 3);
     if (dc < 0)
         return AVERROR_INVALIDDATA;
     if (dc)
         dc = get_xbits(gb, dc);
     dc = dc * qmat[0] + c->prev_dc[plane];
     block[0] = dc;
     c->prev_dc[plane] = dc;
 
     pos = 0;
     while (pos < 63) {
         val = get_vlc2(gb, c->ac_vlc[is_chroma].table, 9, 3);
         if (val < 0)
             return AVERROR_INVALIDDATA;
         pos += val >> 4;
         val &= 0xF;
         if (pos > 63)
             return val ? AVERROR_INVALIDDATA : 0;
         if (val) {
             int nbits = val;
 
             val = get_xbits(gb, nbits);
             val *= qmat[ff_zigzag_direct[pos]];
             block[c->scantable.permutated[pos]] = val;
         }
     }
     return 0;
 }
 
 static inline void yuv2rgb(uint8_t *out, int Y, int U, int V)
 {
     out[0] = av_clip_uint8(Y + (             91881 * V + 32768 >> 16));
     out[1] = av_clip_uint8(Y + (-22554 * U - 46802 * V + 32768 >> 16));
     out[2] = av_clip_uint8(Y + (116130 * U             + 32768 >> 16));
 }
 
 static int jpg_decode_data(JPGContext *c, int width, int height,
                            const uint8_t *src, int src_size,
                            uint8_t *dst, int dst_stride,
                            const uint8_t *mask, int mask_stride, int num_mbs,
                            int swapuv)
 {
     GetBitContext gb;
     uint8_t *tmp;
     int mb_w, mb_h, mb_x, mb_y, i, j;
     int bx, by;
     int unesc_size;
     int ret;
 
     tmp = av_realloc(c->buf, src_size + FF_INPUT_BUFFER_PADDING_SIZE);
     if (!tmp)
         return AVERROR(ENOMEM);
     c->buf = tmp;
     jpg_unescape(src, src_size, c->buf, &unesc_size);
     memset(c->buf + unesc_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
     init_get_bits(&gb, c->buf, unesc_size * 8);
 
     width = FFALIGN(width, 16);
     mb_w  =  width        >> 4;
     mb_h  = (height + 15) >> 4;
 
     if (!num_mbs)
         num_mbs = mb_w * mb_h;
 
     for (i = 0; i < 3; i++)
         c->prev_dc[i] = 1024;
     bx = by = 0;
     for (mb_y = 0; mb_y < mb_h; mb_y++) {
         for (mb_x = 0; mb_x < mb_w; mb_x++) {
             if (mask && !mask[mb_x]) {
                 bx += 16;
                 continue;
             }
             for (j = 0; j < 2; j++) {
                 for (i = 0; i < 2; i++) {
                     if ((ret = jpg_decode_block(c, &gb, 0,
                                                 c->block[i + j * 2])) != 0)
                         return ret;
                     c->dsp.idct(c->block[i + j * 2]);
                 }
             }
             for (i = 1; i < 3; i++) {
                 if ((ret = jpg_decode_block(c, &gb, i, c->block[i + 3])) != 0)
                     return ret;
                 c->dsp.idct(c->block[i + 3]);
             }
 
             for (j = 0; j < 16; j++) {
                 uint8_t *out = dst + bx * 3 + (by + j) * dst_stride;
                 for (i = 0; i < 16; i++) {
                     int Y, U, V;
 
                     Y = c->block[(j >> 3) * 2 + (i >> 3)][(i & 7) + (j & 7) * 8];
                     U = c->block[4 ^ swapuv][(i >> 1) + (j >> 1) * 8] - 128;
                     V = c->block[5 ^ swapuv][(i >> 1) + (j >> 1) * 8] - 128;
                     yuv2rgb(out + i * 3, Y, U, V);
                 }
             }
 
             if (!--num_mbs)
                 return 0;
             bx += 16;
         }
         bx  = 0;
         by += 16;
         if (mask)
             mask += mask_stride;
     }
 
     return 0;
 }
 
 static void kempf_restore_buf(const uint8_t *src, int len,
                               uint8_t *dst, int stride,
                               const uint8_t *jpeg_tile, int tile_stride,
                               int width, int height,
                               const uint8_t *pal, int npal, int tidx)
 {
     GetBitContext gb;
     int i, j, nb, col;
 
     init_get_bits(&gb, src, len * 8);
 
     if (npal <= 2)       nb = 1;
     else if (npal <= 4)  nb = 2;
     else if (npal <= 16) nb = 4;
     else                 nb = 8;
 
     for (j = 0; j < height; j++, dst += stride, jpeg_tile += tile_stride) {
         if (get_bits(&gb, 8))
             continue;
         for (i = 0; i < width; i++) {
             col = get_bits(&gb, nb);
             if (col != tidx)
                 memcpy(dst + i * 3, pal + col * 3, 3);
             else
                 memcpy(dst + i * 3, jpeg_tile + i * 3, 3);
         }
     }
 }
 
 static int kempf_decode_tile(G2MContext *c, int tile_x, int tile_y,
                              const uint8_t *src, int src_size)
 {
     int width, height;
     int hdr, zsize, npal, tidx = -1, ret;
     int i, j;
     const uint8_t *src_end = src + src_size;
     uint8_t pal[768], transp[3];
     uLongf dlen = (c->tile_width + 1) * c->tile_height;
     int sub_type;
     int nblocks, cblocks, bstride;
     int bits, bitbuf, coded;
     uint8_t *dst = c->framebuf + tile_x * c->tile_width * 3 +
                    tile_y * c->tile_height * c->framebuf_stride;
 
     if (src_size < 2)
         return AVERROR_INVALIDDATA;
 
     width  = FFMIN(c->width  - tile_x * c->tile_width,  c->tile_width);
     height = FFMIN(c->height - tile_y * c->tile_height, c->tile_height);
 
     hdr = *src++;
     sub_type = hdr >> 5;
     if (sub_type == 0) {
         int j;
         memcpy(transp, src, 3);
         src += 3;
         for (j = 0; j < height; j++, dst += c->framebuf_stride)
             for (i = 0; i < width; i++)
                 memcpy(dst + i * 3, transp, 3);
         return 0;
     } else if (sub_type == 1) {
         return jpg_decode_data(&c->jc, width, height, src, src_end - src,
                                dst, c->framebuf_stride, NULL, 0, 0, 0);
     }
 
     if (sub_type != 2) {
         memcpy(transp, src, 3);
         src += 3;
     }
     npal = *src++ + 1;
     memcpy(pal, src, npal * 3); src += npal * 3;
     if (sub_type != 2) {
         for (i = 0; i < npal; i++) {
             if (!memcmp(pal + i * 3, transp, 3)) {
                tidx = i;
                break;
             }
         }
     }
 
     if (src_end - src < 2)
         return 0;
     zsize = (src[0] << 8) | src[1]; src += 2;
 
     if (src_end - src < zsize)
         return AVERROR_INVALIDDATA;
 
     ret = uncompress(c->kempf_buf, &dlen, src, zsize);
     if (ret)
         return AVERROR_INVALIDDATA;
     src += zsize;
 
     if (sub_type == 2) {
         kempf_restore_buf(c->kempf_buf, dlen, dst, c->framebuf_stride,
                           NULL, 0, width, height, pal, npal, tidx);
         return 0;
     }
 
     nblocks = *src++ + 1;
     cblocks = 0;
     bstride = FFALIGN(width, 16) >> 4;
     // blocks are coded LSB and we need normal bitreader for JPEG data
     bits = 0;
     for (i = 0; i < (FFALIGN(height, 16) >> 4); i++) {
         for (j = 0; j < (FFALIGN(width, 16) >> 4); j++) {
             if (!bits) {
                 bitbuf = *src++;
                 bits   = 8;
             }
             coded = bitbuf & 1;
             bits--;
             bitbuf >>= 1;
             cblocks += coded;
             if (cblocks > nblocks)
                 return AVERROR_INVALIDDATA;
             c->kempf_flags[j + i * bstride] = coded;
         }
     }
 
     memset(c->jpeg_tile, 0, c->tile_stride * height);
     jpg_decode_data(&c->jc, width, height, src, src_end - src,
                     c->jpeg_tile, c->tile_stride,
                     c->kempf_flags, bstride, nblocks, 0);
 
     kempf_restore_buf(c->kempf_buf, dlen, dst, c->framebuf_stride,
                       c->jpeg_tile, c->tile_stride,
                       width, height, pal, npal, tidx);
 
     return 0;
 }
 
 static int g2m_init_buffers(G2MContext *c)
 {
     int aligned_height;
 

     if (!c->framebuf || c->old_width < c->width || c->old_height < c->height) {

         c->framebuf_stride = FFALIGN(c->width * 3, 16);
         aligned_height     = FFALIGN(c->height,    16);
         av_free(c->framebuf);
         c->framebuf = av_mallocz(c->framebuf_stride * aligned_height);
         if (!c->framebuf)
             return AVERROR(ENOMEM);
     }
     if (!c->synth_tile || !c->jpeg_tile ||
         c->old_tile_w < c->tile_width ||
         c->old_tile_h < c->tile_height) {
         c->tile_stride = FFALIGN(c->tile_width * 3, 16);
         aligned_height = FFALIGN(c->tile_height,    16);
         av_free(c->synth_tile);
         av_free(c->jpeg_tile);

         av_free(c->kempf_buf);
         av_free(c->kempf_flags);

         c->synth_tile  = av_mallocz(c->tile_stride      * aligned_height);
         c->jpeg_tile   = av_mallocz(c->tile_stride      * aligned_height);
         c->kempf_buf   = av_mallocz((c->tile_width + 1) * aligned_height
                                     + FF_INPUT_BUFFER_PADDING_SIZE);
         c->kempf_flags = av_mallocz( c->tile_width      * aligned_height);
         if (!c->synth_tile || !c->jpeg_tile ||
             !c->kempf_buf || !c->kempf_flags)
             return AVERROR(ENOMEM);
     }
 
     return 0;
 }
 

 static int g2m_load_cursor(AVCodecContext *avctx, G2MContext *c,
                            GetByteContext *gb)

 {
     int i, j, k;
     uint8_t *dst;
     uint32_t bits;

     uint32_t cur_size, cursor_w, cursor_h, cursor_stride;
     uint32_t cursor_hot_x, cursor_hot_y;
     int cursor_fmt;
     uint8_t *tmp;

     cur_size      = bytestream2_get_be32(gb);
     cursor_w      = bytestream2_get_byte(gb);
     cursor_h      = bytestream2_get_byte(gb);
     cursor_hot_x  = bytestream2_get_byte(gb);
     cursor_hot_y  = bytestream2_get_byte(gb);
     cursor_fmt    = bytestream2_get_byte(gb);
 
     cursor_stride = cursor_w * 4;
 
     if (cursor_w < 1 || cursor_w > 256 ||
         cursor_h < 1 || cursor_h > 256) {
         av_log(avctx, AV_LOG_ERROR, "Invalid cursor dimensions %dx%d\n",
                cursor_w, cursor_h);
         return AVERROR_INVALIDDATA;
     }
     if (cursor_hot_x > cursor_w || cursor_hot_y > cursor_h) {
         av_log(avctx, AV_LOG_WARNING, "Invalid hotspot position %d,%d\n",
                cursor_hot_x, cursor_hot_y);
         cursor_hot_x = FFMIN(cursor_hot_x, cursor_w - 1);
         cursor_hot_y = FFMIN(cursor_hot_y, cursor_h - 1);
     }
     if (cur_size - 9 > bytestream2_get_bytes_left(gb) ||
         c->cursor_w * c->cursor_h / 4 > cur_size) {
         av_log(avctx, AV_LOG_ERROR, "Invalid cursor data size %d/%d\n",
                cur_size, bytestream2_get_bytes_left(gb));
         return AVERROR_INVALIDDATA;
     }
     if (cursor_fmt != 1 && cursor_fmt != 32) {
         avpriv_report_missing_feature(avctx, "Cursor format %d",
                                       cursor_fmt);
         return AVERROR_PATCHWELCOME;
     }
 

     if (cursor_fmt == 1 && cursor_w % 32) {
         avpriv_report_missing_feature(avctx, "odd monochrome cursor width %d", cursor_w);
         return AVERROR_PATCHWELCOME;
     }
 

     tmp = av_realloc(c->cursor, cursor_stride * cursor_h);
     if (!tmp) {
         av_log(avctx, AV_LOG_ERROR, "Cannot allocate cursor buffer\n");

         return AVERROR(ENOMEM);

     }
 
     c->cursor        = tmp;
     c->cursor_w      = cursor_w;
     c->cursor_h      = cursor_h;
     c->cursor_hot_x  = cursor_hot_x;
     c->cursor_hot_y  = cursor_hot_y;
     c->cursor_fmt    = cursor_fmt;
     c->cursor_stride = cursor_stride;

 
     dst = c->cursor;
     switch (c->cursor_fmt) {
     case 1: // old monochrome
         for (j = 0; j < c->cursor_h; j++) {
             for (i = 0; i < c->cursor_w; i += 32) {
                 bits = bytestream2_get_be32(gb);
                 for (k = 0; k < 32; k++) {
                     dst[0] = !!(bits & 0x80000000);
                     dst += 4;
                     bits <<= 1;
                 }
             }
         }
 
         dst = c->cursor;
         for (j = 0; j < c->cursor_h; j++) {
             for (i = 0; i < c->cursor_w; i += 32) {
                 bits = bytestream2_get_be32(gb);
                 for (k = 0; k < 32; k++) {
                     int mask_bit = !!(bits & 0x80000000);
                     switch (dst[0] * 2 + mask_bit) {
                     case 0:
                         dst[0] = 0xFF; dst[1] = 0x00;
                         dst[2] = 0x00; dst[3] = 0x00;
                         break;
                     case 1:
                         dst[0] = 0xFF; dst[1] = 0xFF;
                         dst[2] = 0xFF; dst[3] = 0xFF;
                         break;
                     default:
                         dst[0] = 0x00; dst[1] = 0x00;
                         dst[2] = 0x00; dst[3] = 0x00;
                     }
                     dst += 4;
                     bits <<= 1;
                 }
             }
         }
         break;
     case 32: // full colour
         /* skip monochrome version of the cursor and decode RGBA instead */
         bytestream2_skip(gb, c->cursor_h * (FFALIGN(c->cursor_w, 32) >> 3));
         for (j = 0; j < c->cursor_h; j++) {
             for (i = 0; i < c->cursor_w; i++) {
                 int val = bytestream2_get_be32(gb);
                 *dst++ = val >>  0;
                 *dst++ = val >>  8;
                 *dst++ = val >> 16;
                 *dst++ = val >> 24;
             }
         }
         break;
     default:
         return AVERROR_PATCHWELCOME;
     }
     return 0;
 }
 
 #define APPLY_ALPHA(src, new, alpha) \
     src = (src * (256 - alpha) + new * alpha) >> 8
 
 static void g2m_paint_cursor(G2MContext *c, uint8_t *dst, int stride)
 {
     int i, j;
     int x, y, w, h;
     const uint8_t *cursor;
 
     if (!c->cursor)
         return;
 
     x = c->cursor_x - c->cursor_hot_x;
     y = c->cursor_y - c->cursor_hot_y;
 
     cursor = c->cursor;
     w      = c->cursor_w;
     h      = c->cursor_h;
 
     if (x + w > c->width)
         w = c->width - x;
     if (y + h > c->height)
         h = c->height - y;
     if (x < 0) {
         w      +=  x;
         cursor += -x * 4;
     } else {
         dst    +=  x * 3;
     }
     if (y < 0) {
         h      +=  y;
         cursor += -y * c->cursor_stride;
     } else {
         dst    +=  y * stride;
     }
     if (w < 0 || h < 0)
         return;
 
     for (j = 0; j < h; j++) {
         for (i = 0; i < w; i++) {
             uint8_t alpha = cursor[i * 4];
             APPLY_ALPHA(dst[i * 3 + 0], cursor[i * 4 + 1], alpha);
             APPLY_ALPHA(dst[i * 3 + 1], cursor[i * 4 + 2], alpha);
             APPLY_ALPHA(dst[i * 3 + 2], cursor[i * 4 + 3], alpha);
         }
         dst    += stride;
         cursor += c->cursor_stride;
     }
 }
 
 static int g2m_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_picture_ptr, AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     G2MContext *c = avctx->priv_data;
     AVFrame *pic = data;
     GetByteContext bc, tbc;
     int magic;
     int got_header = 0;

     uint32_t chunk_size;

     int chunk_type;
     int i;
     int ret;
 
     if (buf_size < 12) {
         av_log(avctx, AV_LOG_ERROR,
                "Frame should have at least 12 bytes, got %d instead\n",
                buf_size);
         return AVERROR_INVALIDDATA;
     }
 
     bytestream2_init(&bc, buf, buf_size);
 
     magic = bytestream2_get_be32(&bc);
     if ((magic & ~0xF) != MKBETAG('G', '2', 'M', '0') ||
         (magic & 0xF) < 2 || (magic & 0xF) > 4) {
         av_log(avctx, AV_LOG_ERROR, "Wrong magic %08X\n", magic);
         return AVERROR_INVALIDDATA;
     }
 
     if ((magic & 0xF) != 4) {
         av_log(avctx, AV_LOG_ERROR, "G2M2 and G2M3 are not yet supported\n");
         return AVERROR(ENOSYS);
     }
 
     while (bytestream2_get_bytes_left(&bc) > 5) {
         chunk_size = bytestream2_get_le32(&bc) - 1;
         chunk_type = bytestream2_get_byte(&bc);
         if (chunk_size > bytestream2_get_bytes_left(&bc)) {
             av_log(avctx, AV_LOG_ERROR, "Invalid chunk size %d type %02X\n",
                    chunk_size, chunk_type);
             break;
         }
         switch (chunk_type) {
         case FRAME_INFO:
             c->got_header = 0;
             if (chunk_size < 21) {
                 av_log(avctx, AV_LOG_ERROR, "Invalid frame info size %d\n",
                        chunk_size);
                 break;
             }
             c->width  = bytestream2_get_be32(&bc);
             c->height = bytestream2_get_be32(&bc);
             if (c->width  < 16 || c->width  > avctx->width ||
                 c->height < 16 || c->height > avctx->height) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid frame dimensions %dx%d\n",
                        c->width, c->height);

                 ret = AVERROR_INVALIDDATA;
                 goto header_fail;

             }
             if (c->width != avctx->width || c->height != avctx->height)
                 avcodec_set_dimensions(avctx, c->width, c->height);
             c->compression = bytestream2_get_be32(&bc);
             if (c->compression != 2 && c->compression != 3) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Unknown compression method %d\n",
                        c->compression);
                 return AVERROR_PATCHWELCOME;
             }
             c->tile_width  = bytestream2_get_be32(&bc);
             c->tile_height = bytestream2_get_be32(&bc);
             if (!c->tile_width || !c->tile_height) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid tile dimensions %dx%d\n",
                        c->tile_width, c->tile_height);

                 ret = AVERROR_INVALIDDATA;
                 goto header_fail;

             }
             c->tiles_x = (c->width  + c->tile_width  - 1) / c->tile_width;
             c->tiles_y = (c->height + c->tile_height - 1) / c->tile_height;
             c->bpp = bytestream2_get_byte(&bc);
             chunk_size -= 21;
             bytestream2_skip(&bc, chunk_size);

             if (g2m_init_buffers(c)) {
                 ret = AVERROR(ENOMEM);
                 goto header_fail;
             }

             got_header = 1;
             break;
         case TILE_DATA:
             if (!c->tiles_x || !c->tiles_y) {
                 av_log(avctx, AV_LOG_WARNING,
                        "No frame header - skipping tile\n");
                 bytestream2_skip(&bc, bytestream2_get_bytes_left(&bc));
                 break;
             }
             if (chunk_size < 2) {
                 av_log(avctx, AV_LOG_ERROR, "Invalid tile data size %d\n",
                        chunk_size);
                 break;
             }
             c->tile_x = bytestream2_get_byte(&bc);
             c->tile_y = bytestream2_get_byte(&bc);
             if (c->tile_x >= c->tiles_x || c->tile_y >= c->tiles_y) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Invalid tile pos %d,%d (in %dx%d grid)\n",
                        c->tile_x, c->tile_y, c->tiles_x, c->tiles_y);
                 break;
             }
             chunk_size -= 2;
             ret = 0;
             switch (c->compression) {
             case COMPR_EPIC_J_B:
                 av_log(avctx, AV_LOG_ERROR,
                        "ePIC j-b compression is not implemented yet\n");
                 return AVERROR(ENOSYS);
             case COMPR_KEMPF_J_B:
                 ret = kempf_decode_tile(c, c->tile_x, c->tile_y,
                                         buf + bytestream2_tell(&bc),
                                         chunk_size);
                 break;
             }
             if (ret && c->framebuf)
                 av_log(avctx, AV_LOG_ERROR, "Error decoding tile %d,%d\n",
                        c->tile_x, c->tile_y);
             bytestream2_skip(&bc, chunk_size);
             break;
         case CURSOR_POS:
             if (chunk_size < 5) {
                 av_log(avctx, AV_LOG_ERROR, "Invalid cursor pos size %d\n",
                        chunk_size);
                 break;
             }
             c->cursor_x = bytestream2_get_be16(&bc);
             c->cursor_y = bytestream2_get_be16(&bc);
             bytestream2_skip(&bc, chunk_size - 4);
             break;
         case CURSOR_SHAPE:
             if (chunk_size < 8) {
                 av_log(avctx, AV_LOG_ERROR, "Invalid cursor data size %d\n",
                        chunk_size);
                 break;
             }
             bytestream2_init(&tbc, buf + bytestream2_tell(&bc),
                              chunk_size - 4);

             g2m_load_cursor(avctx, c, &tbc);

             bytestream2_skip(&bc, chunk_size);
             break;
         case CHUNK_CC:
         case CHUNK_CD:
             bytestream2_skip(&bc, chunk_size);
             break;
         default:
             av_log(avctx, AV_LOG_WARNING, "Skipping chunk type %02X\n",
                    chunk_type);
             bytestream2_skip(&bc, chunk_size);
         }
     }
     if (got_header)
         c->got_header = 1;
 

     if (c->width && c->height && c->framebuf) {

         if ((ret = ff_get_buffer(avctx, pic, 0)) < 0) {
             av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
             return ret;
         }
 
         pic->key_frame = got_header;
         pic->pict_type = got_header ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
 
         for (i = 0; i < avctx->height; i++)
             memcpy(pic->data[0] + i * pic->linesize[0],
                    c->framebuf  + i * c->framebuf_stride,
                    c->width * 3);
         g2m_paint_cursor(c, pic->data[0], pic->linesize[0]);
 
         *got_picture_ptr = 1;
     }
 
     return buf_size;

 header_fail:
     c->width   = c->height  = 0;
     c->tiles_x = c->tiles_y = 0;
     return ret;

 }
 
 static av_cold int g2m_decode_init(AVCodecContext *avctx)
 {
     G2MContext * const c = avctx->priv_data;
     int ret;
 
     if ((ret = jpg_init(avctx, &c->jc)) != 0) {
         av_log(avctx, AV_LOG_ERROR, "Cannot initialise VLCs\n");
         jpg_free_context(&c->jc);
         return AVERROR(ENOMEM);
     }
 

     avctx->pix_fmt     = AV_PIX_FMT_RGB24;

 
     return 0;
 }
 
 static av_cold int g2m_decode_end(AVCodecContext *avctx)
 {
     G2MContext * const c = avctx->priv_data;
 
     jpg_free_context(&c->jc);
 
     av_freep(&c->kempf_buf);
     av_freep(&c->kempf_flags);
     av_freep(&c->synth_tile);
     av_freep(&c->jpeg_tile);
     av_freep(&c->cursor);
     av_freep(&c->framebuf);
 
     return 0;
 }
 
 AVCodec ff_g2m_decoder = {
     .name           = "g2m",
     .long_name      = NULL_IF_CONFIG_SMALL("Go2Meeting"),
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_G2M,
     .priv_data_size = sizeof(G2MContext),
     .init           = g2m_decode_init,
     .close          = g2m_decode_end,
     .decode         = g2m_decode_frame,
     .capabilities   = CODEC_CAP_DR1,
 };