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"

Go to the source code of this file.

Data Structures
struct	hnode
struct	IdcinContext

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

Functions
static int	huff_smallest_node (hnode *hnodes, int num_hnodes)
	Find the lowest probability node in a Huffman table, and mark it as being assigned to a higher probability.
static av_cold void	huff_build_tree (IdcinContext *s, int prev)
static av_cold int	idcin_decode_init (AVCodecContext *avctx)
static int	idcin_decode_vlcs (IdcinContext *s, AVFrame *frame)
static int	idcin_decode_frame (AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)

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.

Definition in file idcinvideo.c.

Macro Definition Documentation

#define HUFFMAN_TABLE_SIZE   64 * 1024

Definition at line 55 of file idcinvideo.c.

Referenced by idcin_decode_init().

#define HUF_TOKENS   256

Definition at line 56 of file idcinvideo.c.

Referenced by huff_build_tree(), idcin_decode_init(), and idcin_decode_vlcs().

#define PALETTE_COUNT   256

Definition at line 57 of file idcinvideo.c.

Function Documentation

static int huff_smallest_node ( hnode *  hnodes, int  num_hnodes  )

static

Find the lowest probability node in a Huffman table, and mark it as being assigned to a higher probability.

Returns

the node index of the lowest unused node, or -1 if all nodes are used.

Definition at line 85 of file idcinvideo.c.

Referenced by huff_build_tree().

static av_cold void huff_build_tree ( IdcinContext *  s, int  prev  )

static

Definition at line 117 of file idcinvideo.c.

Referenced by idcin_decode_init().

static av_cold int idcin_decode_init ( AVCodecContext *  avctx )

static

Definition at line 147 of file idcinvideo.c.

static int idcin_decode_vlcs ( IdcinContext *  s, AVFrame *  frame  )

static

Definition at line 173 of file idcinvideo.c.

Referenced by idcin_decode_frame().

static int idcin_decode_frame ( AVCodecContext *  avctx, void *  data, int *  got_frame, AVPacket *  avpkt  )

static

Definition at line 211 of file idcinvideo.c.

Variable Documentation

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   = CODEC_CAP_DR1,
}

Definition at line 244 of file idcinvideo.c.