libavcodec/hnm4video.c - third_party/ffmpeg - Git at Google

 /*
  * Cryo Interactive Entertainment HNM4 video decoder
  *
  * Copyright (c) 2012 David Kment
  *
  * 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
  */

 #include <string.h>

 #include "libavutil/imgutils.h"
 #include "libavutil/internal.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/mem.h"
 #include "avcodec.h"
 #include "bytestream.h"
 #include "internal.h"

 #define HNM4_CHUNK_ID_PL 19536
 #define HNM4_CHUNK_ID_IZ 23113
 #define HNM4_CHUNK_ID_IU 21833
 #define HNM4_CHUNK_ID_SD 17491

 typedef struct Hnm4VideoContext {
     uint8_t version;
     int width;
     int height;
     uint8_t *current;
     uint8_t *previous;
     uint8_t *buffer1;
     uint8_t *buffer2;
     uint8_t *processed;
     uint32_t palette[256];
 } Hnm4VideoContext;

 static int getbit(GetByteContext *gb, uint32_t *bitbuf, int *bits)
 {
     int ret;

     if (!*bits) {
         *bitbuf = bytestream2_get_le32(gb);
         *bits = 32;
     }

     ret = *bitbuf >> 31;
     *bitbuf <<= 1;
     (*bits)--;

     return ret;
 }

 static void unpack_intraframe(AVCodecContext *avctx, uint8_t *src,
                               uint32_t size)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     GetByteContext gb;
     uint32_t bitbuf = 0, writeoffset = 0, count = 0;
     uint16_t word;
     int32_t offset;
     int bits = 0;

     bytestream2_init(&gb, src, size);

     while (bytestream2_tell(&gb) < size) {
         if (getbit(&gb, &bitbuf, &bits)) {
             if (writeoffset >= hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Attempting to write out of bounds\n");
                 break;
             }
             hnm->current[writeoffset++] = bytestream2_get_byte(&gb);
         } else {
             if (getbit(&gb, &bitbuf, &bits)) {
                 word   = bytestream2_get_le16(&gb);
                 count  = word & 0x07;
                 offset = (word >> 3) - 0x2000;
                 if (!count)
                     count = bytestream2_get_byte(&gb);
                 if (!count)
                     return;
             } else {
                 count  = getbit(&gb, &bitbuf, &bits) * 2;
                 count += getbit(&gb, &bitbuf, &bits);
                 offset = bytestream2_get_byte(&gb) - 0x0100;
             }
             count  += 2;
             offset += writeoffset;
             if (offset < 0 || offset + count >= hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                 break;
             } else if (writeoffset + count >= hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Attempting to write out of bounds\n");
                 break;
             }
             while (count--) {
                 hnm->current[writeoffset++] = hnm->current[offset++];
             }
         }
     }
 }

 static void postprocess_current_frame(AVCodecContext *avctx)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     uint32_t x, y, src_x, src_y;

     for (y = 0; y < hnm->height; y++) {
         src_y = y - (y % 2);
         src_x = src_y * hnm->width + (y % 2);
         for (x = 0; x < hnm->width; x++) {
             hnm->processed[(y * hnm->width) + x] = hnm->current[src_x];
             src_x += 2;
         }
     }
 }

 static void copy_processed_frame(AVCodecContext *avctx, AVFrame *frame)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     uint8_t *src = hnm->processed;
     uint8_t *dst = frame->data[0];
     int y;

     for (y = 0; y < hnm->height; y++) {
         memcpy(dst, src, hnm->width);
         src += hnm->width;
         dst += frame->linesize[0];
     }
 }

 static void decode_interframe_v4(AVCodecContext *avctx, uint8_t *src, uint32_t size)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     GetByteContext gb;
     uint32_t writeoffset = 0;
     int count, left, offset;
     uint8_t tag, previous, backline, backward, swap;

     bytestream2_init(&gb, src, size);

     while (bytestream2_tell(&gb) < size) {
         count = bytestream2_peek_byte(&gb) & 0x1F;
         if (count == 0) {
             tag = bytestream2_get_byte(&gb) & 0xE0;
             tag = tag >> 5;

             if (tag == 0) {
                 if (writeoffset + 2 > hnm->width * hnm->height) {
                     av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
                     break;
                 }
                 hnm->current[writeoffset++] = bytestream2_get_byte(&gb);
                 hnm->current[writeoffset++] = bytestream2_get_byte(&gb);
             } else if (tag == 1) {
                 writeoffset += bytestream2_get_byte(&gb) * 2;
             } else if (tag == 2) {
                 count = bytestream2_get_le16(&gb);
                 count *= 2;
                 writeoffset += count;
             } else if (tag == 3) {
                 count = bytestream2_get_byte(&gb) * 2;
                 if (writeoffset + count > hnm->width * hnm->height) {
                     av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
                     break;
                 }
                 while (count > 0) {
                     hnm->current[writeoffset++] = bytestream2_peek_byte(&gb);
                     count--;
                 }
                 bytestream2_skip(&gb, 1);
             } else {
                 break;
             }
             if (writeoffset > hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
                 break;
             }
         } else {
             previous = bytestream2_peek_byte(&gb) & 0x20;
             backline = bytestream2_peek_byte(&gb) & 0x40;
             backward = bytestream2_peek_byte(&gb) & 0x80;
             bytestream2_skip(&gb, 1);
             swap   = bytestream2_peek_byte(&gb) & 0x01;
             offset = bytestream2_get_le16(&gb);
             offset = (offset >> 1) & 0x7FFF;
             offset = writeoffset + (offset * 2) - 0x8000;

             left = count;

             if (!backward && offset + 2*count > hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                 break;
             } else if (backward && offset + 1 >= hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                 break;
             } else if (writeoffset + 2*count > hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR,
                        "Attempting to write out of bounds\n");
                 break;
             }
             if(backward) {
                 if (offset < (!!backline)*(2 * hnm->width - 1) + 2*(left-1)) {
                     av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                     break;
                 }
             } else {
                 if (offset < (!!backline)*(2 * hnm->width - 1)) {
                     av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                     break;
                 }
             }

             if (previous) {
                 while (left > 0) {
                     if (backline) {
                         hnm->current[writeoffset++] = hnm->previous[offset - (2 * hnm->width) + 1];
                         hnm->current[writeoffset++] = hnm->previous[offset++];
                         offset++;
                     } else {
                         hnm->current[writeoffset++] = hnm->previous[offset++];
                         hnm->current[writeoffset++] = hnm->previous[offset++];
                     }
                     if (backward)
                         offset -= 4;
                     left--;
                 }
             } else {
                 while (left > 0) {
                     if (backline) {
                         hnm->current[writeoffset++] = hnm->current[offset - (2 * hnm->width) + 1];
                         hnm->current[writeoffset++] = hnm->current[offset++];
                         offset++;
                     } else {
                         hnm->current[writeoffset++] = hnm->current[offset++];
                         hnm->current[writeoffset++] = hnm->current[offset++];
                     }
                     if (backward)
                         offset -= 4;
                     left--;
                 }
             }

             if (swap) {
                 left         = count;
                 writeoffset -= count * 2;
                 while (left > 0) {
                     swap = hnm->current[writeoffset];
                     hnm->current[writeoffset] = hnm->current[writeoffset + 1];
                     hnm->current[writeoffset + 1] = swap;
                     left--;
                     writeoffset += 2;
                 }
             }
         }
     }
 }

 static void decode_interframe_v4a(AVCodecContext *avctx, uint8_t *src,
                                   uint32_t size)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     GetByteContext gb;
     uint32_t writeoffset = 0, offset;
     uint8_t tag, count, previous, delta;

     bytestream2_init(&gb, src, size);

     while (bytestream2_tell(&gb) < size) {
         count = bytestream2_peek_byte(&gb) & 0x3F;
         if (count == 0) {
             tag = bytestream2_get_byte(&gb) & 0xC0;
             tag = tag >> 6;
             if (tag == 0) {
                 writeoffset += bytestream2_get_byte(&gb);
             } else if (tag == 1) {
                 if (writeoffset + hnm->width >= hnm->width * hnm->height) {
                     av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
                     break;
                 }
                 hnm->current[writeoffset]              = bytestream2_get_byte(&gb);
                 hnm->current[writeoffset + hnm->width] = bytestream2_get_byte(&gb);
                 writeoffset++;
             } else if (tag == 2) {
                 writeoffset += hnm->width;
             } else if (tag == 3) {
                 break;
             }
             if (writeoffset > hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
                 break;
             }
         } else {
             delta    = bytestream2_peek_byte(&gb) & 0x80;
             previous = bytestream2_peek_byte(&gb) & 0x40;
             bytestream2_skip(&gb, 1);

             offset  = writeoffset;
             offset += bytestream2_get_le16(&gb);

             if (delta) {
                 if (offset < 0x10000) {
                     av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                     break;
                 }
                 offset -= 0x10000;
             }

             if (offset + hnm->width + count >= hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
                 break;
             } else if (writeoffset + hnm->width + count >= hnm->width * hnm->height) {
                 av_log(avctx, AV_LOG_ERROR, "Attempting to write out of bounds\n");
                 break;
             }

             if (previous) {
                 while (count > 0) {
                     hnm->current[writeoffset]              = hnm->previous[offset];
                     hnm->current[writeoffset + hnm->width] = hnm->previous[offset + hnm->width];
                     writeoffset++;
                     offset++;
                     count--;
                 }
             } else {
                 while (count > 0) {
                     hnm->current[writeoffset]              = hnm->current[offset];
                     hnm->current[writeoffset + hnm->width] = hnm->current[offset + hnm->width];
                     writeoffset++;
                     offset++;
                     count--;
                 }
             }
         }
     }
 }

 static void hnm_update_palette(AVCodecContext *avctx, uint8_t *src,
                                uint32_t size)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     GetByteContext gb;
     uint8_t start, writeoffset;
     uint16_t count;
     int eight_bit_colors;

     eight_bit_colors = src[7] & 0x80 && hnm->version == 0x4a;

     // skip first 8 bytes
     bytestream2_init(&gb, src + 8, size - 8);

     while (bytestream2_tell(&gb) < size - 8) {
         start = bytestream2_get_byte(&gb);
         count = bytestream2_get_byte(&gb);
         if (start == 255 && count == 255)
             break;
         if (count == 0)
             count = 256;
         writeoffset = start;
         while (count > 0) {
             hnm->palette[writeoffset] = bytestream2_get_be24(&gb);
             if (!eight_bit_colors)
                 hnm->palette[writeoffset] <<= 2;
             count--;
             writeoffset++;
         }
     }
 }

 static void hnm_flip_buffers(Hnm4VideoContext *hnm)
 {
     uint8_t *temp;

     temp          = hnm->current;
     hnm->current  = hnm->previous;
     hnm->previous = temp;
 }

 static int hnm_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_frame, AVPacket *avpkt)
 {
     AVFrame *frame = data;
     Hnm4VideoContext *hnm = avctx->priv_data;
     int ret;
     uint16_t chunk_id;

     if (avpkt->size < 8) {
         av_log(avctx, AV_LOG_ERROR, "packet too small\n");
         return AVERROR_INVALIDDATA;
     }

     chunk_id = AV_RL16(avpkt->data + 4);

     if (chunk_id == HNM4_CHUNK_ID_PL) {
         hnm_update_palette(avctx, avpkt->data, avpkt->size);
     } else if (chunk_id == HNM4_CHUNK_ID_IZ) {
         if (avpkt->size < 12) {
             av_log(avctx, AV_LOG_ERROR, "packet too small\n");
             return AVERROR_INVALIDDATA;
         }
         if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
             return ret;

         unpack_intraframe(avctx, avpkt->data + 12, avpkt->size - 12);
         memcpy(hnm->previous, hnm->current, hnm->width * hnm->height);
         if (hnm->version == 0x4a)
             memcpy(hnm->processed, hnm->current, hnm->width * hnm->height);
         else
             postprocess_current_frame(avctx);
         copy_processed_frame(avctx, frame);
         frame->pict_type = AV_PICTURE_TYPE_I;
         frame->key_frame = 1;
         memcpy(frame->data[1], hnm->palette, 256 * 4);
         *got_frame = 1;
     } else if (chunk_id == HNM4_CHUNK_ID_IU) {
         if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
             return ret;

         if (hnm->version == 0x4a) {
             decode_interframe_v4a(avctx, avpkt->data + 8, avpkt->size - 8);
             memcpy(hnm->processed, hnm->current, hnm->width * hnm->height);
         } else {
             decode_interframe_v4(avctx, avpkt->data + 8, avpkt->size - 8);
             postprocess_current_frame(avctx);
         }
         copy_processed_frame(avctx, frame);
         frame->pict_type = AV_PICTURE_TYPE_P;
         frame->key_frame = 0;
         memcpy(frame->data[1], hnm->palette, 256 * 4);
         *got_frame = 1;
         hnm_flip_buffers(hnm);
     } else {
         av_log(avctx, AV_LOG_ERROR, "invalid chunk id: %d\n", chunk_id);
         return AVERROR_INVALIDDATA;
     }

     return avpkt->size;
 }

 static av_cold int hnm_decode_init(AVCodecContext *avctx)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;
     int ret;

     if (avctx->extradata_size < 1) {
         av_log(avctx, AV_LOG_ERROR,
                "Extradata missing, decoder requires version number\n");
         return AVERROR_INVALIDDATA;
     }

     ret = av_image_check_size(avctx->width, avctx->height, 0, avctx);
     if (ret < 0)
         return ret;

     hnm->version   = avctx->extradata[0];
     avctx->pix_fmt = AV_PIX_FMT_PAL8;
     hnm->width     = avctx->width;
     hnm->height    = avctx->height;
     hnm->buffer1   = av_mallocz(avctx->width * avctx->height);
     hnm->buffer2   = av_mallocz(avctx->width * avctx->height);
     hnm->processed = av_mallocz(avctx->width * avctx->height);

     if (   !hnm->buffer1 || !hnm->buffer2 || !hnm->processed
         || avctx->width * avctx->height == 0
         || avctx->height % 2) {
         av_log(avctx, AV_LOG_ERROR, "av_mallocz() failed\n");
         av_freep(&hnm->buffer1);
         av_freep(&hnm->buffer2);
         av_freep(&hnm->processed);
         return AVERROR(ENOMEM);
     }

     hnm->current  = hnm->buffer1;
     hnm->previous = hnm->buffer2;

     return 0;
 }

 static av_cold int hnm_decode_end(AVCodecContext *avctx)
 {
     Hnm4VideoContext *hnm = avctx->priv_data;

     av_freep(&hnm->buffer1);
     av_freep(&hnm->buffer2);
     av_freep(&hnm->processed);

     return 0;
 }

 AVCodec ff_hnm4_video_decoder = {
     .name           = "hnm4video",
     .long_name      = NULL_IF_CONFIG_SMALL("HNM 4 video"),
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_HNM4_VIDEO,
     .priv_data_size = sizeof(Hnm4VideoContext),
     .init           = hnm_decode_init,
     .close          = hnm_decode_end,
     .decode         = hnm_decode_frame,
     .capabilities   = AV_CODEC_CAP_DR1,
 };
	/*
	* Cryo Interactive Entertainment HNM4 video decoder
	*
	* Copyright (c) 2012 David Kment
	*
	* 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
	*/

	#include <string.h>

	#include "libavutil/imgutils.h"
	#include "libavutil/internal.h"
	#include "libavutil/intreadwrite.h"
	#include "libavutil/mem.h"
	#include "avcodec.h"
	#include "bytestream.h"
	#include "internal.h"

	#define HNM4_CHUNK_ID_PL 19536
	#define HNM4_CHUNK_ID_IZ 23113
	#define HNM4_CHUNK_ID_IU 21833
	#define HNM4_CHUNK_ID_SD 17491

	typedef struct Hnm4VideoContext {
	uint8_t version;
	int width;
	int height;
	uint8_t *current;
	uint8_t *previous;
	uint8_t *buffer1;
	uint8_t *buffer2;
	uint8_t *processed;
	uint32_t palette[256];
	} Hnm4VideoContext;

	static int getbit(GetByteContext gb, uint32_t bitbuf, int *bits)
	{
	int ret;

	if (!*bits) {
	*bitbuf = bytestream2_get_le32(gb);
	*bits = 32;
	}

	ret = *bitbuf >> 31;
	*bitbuf <<= 1;
	(*bits)--;

	return ret;
	}

	static void unpack_intraframe(AVCodecContext avctx, uint8_t src,
	uint32_t size)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	GetByteContext gb;
	uint32_t bitbuf = 0, writeoffset = 0, count = 0;
	uint16_t word;
	int32_t offset;
	int bits = 0;

	bytestream2_init(&gb, src, size);

	while (bytestream2_tell(&gb) < size) {
	if (getbit(&gb, &bitbuf, &bits)) {
	if (writeoffset >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR,
	"Attempting to write out of bounds\n");
	break;
	}
	hnm->current[writeoffset++] = bytestream2_get_byte(&gb);
	} else {
	if (getbit(&gb, &bitbuf, &bits)) {
	word = bytestream2_get_le16(&gb);
	count = word & 0x07;
	offset = (word >> 3) - 0x2000;
	if (!count)
	count = bytestream2_get_byte(&gb);
	if (!count)
	return;
	} else {
	count = getbit(&gb, &bitbuf, &bits) * 2;
	count += getbit(&gb, &bitbuf, &bits);
	offset = bytestream2_get_byte(&gb) - 0x0100;
	}
	count += 2;
	offset += writeoffset;
	if (offset < 0 \|\| offset + count >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	} else if (writeoffset + count >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR,
	"Attempting to write out of bounds\n");
	break;
	}
	while (count--) {
	hnm->current[writeoffset++] = hnm->current[offset++];
	}
	}
	}
	}

	static void postprocess_current_frame(AVCodecContext *avctx)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	uint32_t x, y, src_x, src_y;

	for (y = 0; y < hnm->height; y++) {
	src_y = y - (y % 2);
	src_x = src_y * hnm->width + (y % 2);
	for (x = 0; x < hnm->width; x++) {
	hnm->processed[(y * hnm->width) + x] = hnm->current[src_x];
	src_x += 2;
	}
	}
	}

	static void copy_processed_frame(AVCodecContext avctx, AVFrame frame)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	uint8_t *src = hnm->processed;
	uint8_t *dst = frame->data[0];
	int y;

	for (y = 0; y < hnm->height; y++) {
	memcpy(dst, src, hnm->width);
	src += hnm->width;
	dst += frame->linesize[0];
	}
	}

	static void decode_interframe_v4(AVCodecContext avctx, uint8_t src, uint32_t size)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	GetByteContext gb;
	uint32_t writeoffset = 0;
	int count, left, offset;
	uint8_t tag, previous, backline, backward, swap;

	bytestream2_init(&gb, src, size);

	while (bytestream2_tell(&gb) < size) {
	count = bytestream2_peek_byte(&gb) & 0x1F;
	if (count == 0) {
	tag = bytestream2_get_byte(&gb) & 0xE0;
	tag = tag >> 5;

	if (tag == 0) {
	if (writeoffset + 2 > hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
	break;
	}
	hnm->current[writeoffset++] = bytestream2_get_byte(&gb);
	hnm->current[writeoffset++] = bytestream2_get_byte(&gb);
	} else if (tag == 1) {
	writeoffset += bytestream2_get_byte(&gb) * 2;
	} else if (tag == 2) {
	count = bytestream2_get_le16(&gb);
	count *= 2;
	writeoffset += count;
	} else if (tag == 3) {
	count = bytestream2_get_byte(&gb) * 2;
	if (writeoffset + count > hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
	break;
	}
	while (count > 0) {
	hnm->current[writeoffset++] = bytestream2_peek_byte(&gb);
	count--;
	}
	bytestream2_skip(&gb, 1);
	} else {
	break;
	}
	if (writeoffset > hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
	break;
	}
	} else {
	previous = bytestream2_peek_byte(&gb) & 0x20;
	backline = bytestream2_peek_byte(&gb) & 0x40;
	backward = bytestream2_peek_byte(&gb) & 0x80;
	bytestream2_skip(&gb, 1);
	swap = bytestream2_peek_byte(&gb) & 0x01;
	offset = bytestream2_get_le16(&gb);
	offset = (offset >> 1) & 0x7FFF;
	offset = writeoffset + (offset * 2) - 0x8000;

	left = count;

	if (!backward && offset + 2count > hnm->width hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	} else if (backward && offset + 1 >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	} else if (writeoffset + 2count > hnm->width hnm->height) {
	av_log(avctx, AV_LOG_ERROR,
	"Attempting to write out of bounds\n");
	break;
	}
	if(backward) {
	if (offset < (!!backline)(2 hnm->width - 1) + 2*(left-1)) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	}
	} else {
	if (offset < (!!backline)(2 hnm->width - 1)) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	}
	}

	if (previous) {
	while (left > 0) {
	if (backline) {
	hnm->current[writeoffset++] = hnm->previous[offset - (2 * hnm->width) + 1];
	hnm->current[writeoffset++] = hnm->previous[offset++];
	offset++;
	} else {
	hnm->current[writeoffset++] = hnm->previous[offset++];
	hnm->current[writeoffset++] = hnm->previous[offset++];
	}
	if (backward)
	offset -= 4;
	left--;
	}
	} else {
	while (left > 0) {
	if (backline) {
	hnm->current[writeoffset++] = hnm->current[offset - (2 * hnm->width) + 1];
	hnm->current[writeoffset++] = hnm->current[offset++];
	offset++;
	} else {
	hnm->current[writeoffset++] = hnm->current[offset++];
	hnm->current[writeoffset++] = hnm->current[offset++];
	}
	if (backward)
	offset -= 4;
	left--;
	}
	}

	if (swap) {
	left = count;
	writeoffset -= count * 2;
	while (left > 0) {
	swap = hnm->current[writeoffset];
	hnm->current[writeoffset] = hnm->current[writeoffset + 1];
	hnm->current[writeoffset + 1] = swap;
	left--;
	writeoffset += 2;
	}
	}
	}
	}
	}

	static void decode_interframe_v4a(AVCodecContext avctx, uint8_t src,
	uint32_t size)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	GetByteContext gb;
	uint32_t writeoffset = 0, offset;
	uint8_t tag, count, previous, delta;

	bytestream2_init(&gb, src, size);

	while (bytestream2_tell(&gb) < size) {
	count = bytestream2_peek_byte(&gb) & 0x3F;
	if (count == 0) {
	tag = bytestream2_get_byte(&gb) & 0xC0;
	tag = tag >> 6;
	if (tag == 0) {
	writeoffset += bytestream2_get_byte(&gb);
	} else if (tag == 1) {
	if (writeoffset + hnm->width >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
	break;
	}
	hnm->current[writeoffset] = bytestream2_get_byte(&gb);
	hnm->current[writeoffset + hnm->width] = bytestream2_get_byte(&gb);
	writeoffset++;
	} else if (tag == 2) {
	writeoffset += hnm->width;
	} else if (tag == 3) {
	break;
	}
	if (writeoffset > hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "writeoffset out of bounds\n");
	break;
	}
	} else {
	delta = bytestream2_peek_byte(&gb) & 0x80;
	previous = bytestream2_peek_byte(&gb) & 0x40;
	bytestream2_skip(&gb, 1);

	offset = writeoffset;
	offset += bytestream2_get_le16(&gb);

	if (delta) {
	if (offset < 0x10000) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	}
	offset -= 0x10000;
	}

	if (offset + hnm->width + count >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to read out of bounds\n");
	break;
	} else if (writeoffset + hnm->width + count >= hnm->width * hnm->height) {
	av_log(avctx, AV_LOG_ERROR, "Attempting to write out of bounds\n");
	break;
	}

	if (previous) {
	while (count > 0) {
	hnm->current[writeoffset] = hnm->previous[offset];
	hnm->current[writeoffset + hnm->width] = hnm->previous[offset + hnm->width];
	writeoffset++;
	offset++;
	count--;
	}
	} else {
	while (count > 0) {
	hnm->current[writeoffset] = hnm->current[offset];
	hnm->current[writeoffset + hnm->width] = hnm->current[offset + hnm->width];
	writeoffset++;
	offset++;
	count--;
	}
	}
	}
	}
	}

	static void hnm_update_palette(AVCodecContext avctx, uint8_t src,
	uint32_t size)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	GetByteContext gb;
	uint8_t start, writeoffset;
	uint16_t count;
	int eight_bit_colors;

	eight_bit_colors = src[7] & 0x80 && hnm->version == 0x4a;

	// skip first 8 bytes
	bytestream2_init(&gb, src + 8, size - 8);

	while (bytestream2_tell(&gb) < size - 8) {
	start = bytestream2_get_byte(&gb);
	count = bytestream2_get_byte(&gb);
	if (start == 255 && count == 255)
	break;
	if (count == 0)
	count = 256;
	writeoffset = start;
	while (count > 0) {
	hnm->palette[writeoffset] = bytestream2_get_be24(&gb);
	if (!eight_bit_colors)
	hnm->palette[writeoffset] <<= 2;
	count--;
	writeoffset++;
	}
	}
	}

	static void hnm_flip_buffers(Hnm4VideoContext *hnm)
	{
	uint8_t *temp;

	temp = hnm->current;
	hnm->current = hnm->previous;
	hnm->previous = temp;
	}

	static int hnm_decode_frame(AVCodecContext avctx, void data,
	int got_frame, AVPacket avpkt)
	{
	AVFrame *frame = data;
	Hnm4VideoContext *hnm = avctx->priv_data;
	int ret;
	uint16_t chunk_id;

	if (avpkt->size < 8) {
	av_log(avctx, AV_LOG_ERROR, "packet too small\n");
	return AVERROR_INVALIDDATA;
	}

	chunk_id = AV_RL16(avpkt->data + 4);

	if (chunk_id == HNM4_CHUNK_ID_PL) {
	hnm_update_palette(avctx, avpkt->data, avpkt->size);
	} else if (chunk_id == HNM4_CHUNK_ID_IZ) {
	if (avpkt->size < 12) {
	av_log(avctx, AV_LOG_ERROR, "packet too small\n");
	return AVERROR_INVALIDDATA;
	}
	if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
	return ret;

	unpack_intraframe(avctx, avpkt->data + 12, avpkt->size - 12);
	memcpy(hnm->previous, hnm->current, hnm->width * hnm->height);
	if (hnm->version == 0x4a)
	memcpy(hnm->processed, hnm->current, hnm->width * hnm->height);
	else
	postprocess_current_frame(avctx);
	copy_processed_frame(avctx, frame);
	frame->pict_type = AV_PICTURE_TYPE_I;
	frame->key_frame = 1;
	memcpy(frame->data[1], hnm->palette, 256 * 4);
	*got_frame = 1;
	} else if (chunk_id == HNM4_CHUNK_ID_IU) {
	if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
	return ret;

	if (hnm->version == 0x4a) {
	decode_interframe_v4a(avctx, avpkt->data + 8, avpkt->size - 8);
	memcpy(hnm->processed, hnm->current, hnm->width * hnm->height);
	} else {
	decode_interframe_v4(avctx, avpkt->data + 8, avpkt->size - 8);
	postprocess_current_frame(avctx);
	}
	copy_processed_frame(avctx, frame);
	frame->pict_type = AV_PICTURE_TYPE_P;
	frame->key_frame = 0;
	memcpy(frame->data[1], hnm->palette, 256 * 4);
	*got_frame = 1;
	hnm_flip_buffers(hnm);
	} else {
	av_log(avctx, AV_LOG_ERROR, "invalid chunk id: %d\n", chunk_id);
	return AVERROR_INVALIDDATA;
	}

	return avpkt->size;
	}

	static av_cold int hnm_decode_init(AVCodecContext *avctx)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;
	int ret;

	if (avctx->extradata_size < 1) {
	av_log(avctx, AV_LOG_ERROR,
	"Extradata missing, decoder requires version number\n");
	return AVERROR_INVALIDDATA;
	}

	ret = av_image_check_size(avctx->width, avctx->height, 0, avctx);
	if (ret < 0)
	return ret;

	hnm->version = avctx->extradata[0];
	avctx->pix_fmt = AV_PIX_FMT_PAL8;
	hnm->width = avctx->width;
	hnm->height = avctx->height;
	hnm->buffer1 = av_mallocz(avctx->width * avctx->height);
	hnm->buffer2 = av_mallocz(avctx->width * avctx->height);
	hnm->processed = av_mallocz(avctx->width * avctx->height);

	if ( !hnm->buffer1 \|\| !hnm->buffer2 \|\| !hnm->processed
	\|\| avctx->width * avctx->height == 0
	\|\| avctx->height % 2) {
	av_log(avctx, AV_LOG_ERROR, "av_mallocz() failed\n");
	av_freep(&hnm->buffer1);
	av_freep(&hnm->buffer2);
	av_freep(&hnm->processed);
	return AVERROR(ENOMEM);
	}

	hnm->current = hnm->buffer1;
	hnm->previous = hnm->buffer2;

	return 0;
	}

	static av_cold int hnm_decode_end(AVCodecContext *avctx)
	{
	Hnm4VideoContext *hnm = avctx->priv_data;

	av_freep(&hnm->buffer1);
	av_freep(&hnm->buffer2);
	av_freep(&hnm->processed);

	return 0;
	}

	AVCodec ff_hnm4_video_decoder = {
	.name = "hnm4video",
	.long_name = NULL_IF_CONFIG_SMALL("HNM 4 video"),
	.type = AVMEDIA_TYPE_VIDEO,
	.id = AV_CODEC_ID_HNM4_VIDEO,
	.priv_data_size = sizeof(Hnm4VideoContext),
	.init = hnm_decode_init,
	.close = hnm_decode_end,
	.decode = hnm_decode_frame,
	.capabilities = AV_CODEC_CAP_DR1,
	};