idcinvideo.c File Reference

id Quake II Cin Video Decoder by Dr. More...

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "avcodec.h"
#include "internal.h"
#include "libavutil/internal.h"

Classes
struct	hnode
struct	IdcinContext

Macros
#define	HUFFMAN_TABLE_SIZE   64 * 1024
#define	HUF_TOKENS   256
#define	PALETTE_COUNT   256

Typedefs
typedef struct hnode	hnode
typedef struct IdcinContext	IdcinContext

Variables
AVCodec	ff_idcin_decoder

Detailed Description

id Quake II Cin Video Decoder by Dr.

Tim Ferguson For more information about the id CIN format, visit: http://www.csse.monash.edu.au/~timf/

This video decoder outputs PAL8 colorspace data. Interacting with this decoder is a little involved. During initialization, the demuxer must transmit the 65536-byte Huffman table(s) to the decoder via extradata. Then, whenever a palette change is encountered while demuxing the file, the demuxer must use the same extradata space to transmit an AVPaletteControl structure.

id CIN video is purely Huffman-coded, intraframe-only codec. It achieves a little more compression by exploiting the fact that adjacent pixels tend to be similar.

Note that this decoder could use libavcodec's optimized VLC facilities rather than naive, tree-based Huffman decoding. However, there are 256 Huffman tables. Plus, the VLC bit coding order is right -> left instead or left -> right, so all of the bits would have to be reversed. Further, the original Quake II implementation likely used a similar naive decoding algorithm and it worked fine on much lower spec machines.

Variable Documentation

ff_idcin_decoder

AVCodec ff_idcin_decoder

Initial value:

= {
    .name           = "idcinvideo",
    .long_name      = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_IDCIN,
    .priv_data_size = sizeof(IdcinContext),
    .init           = idcin_decode_init,
    .decode         = idcin_decode_frame,
    .capabilities   = AV_CODEC_CAP_DR1,
}