xan.c File Reference

Xan video decoder for Wing Commander III computer game by Mario Brito (mbrit.nosp@m.o@st.nosp@m.udent.nosp@m..dei.nosp@m..uc.p.nosp@m.t) and Mike Melanson (melan.nosp@m.son@.nosp@m.pcisy.nosp@m.s.ne.nosp@m.t) More...

#include <string.h>
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "avcodec.h"
#include "bytestream.h"
#include "codec_internal.h"
#include "decode.h"
#include "get_bits.h"

Go to the source code of this file.

Data Structures
struct	XanContext

Macros
#define	BITSTREAM_READER_LE
#define	RUNTIME_GAMMA   0
#define	VGA__TAG   MKTAG('V', 'G', 'A', ' ')
#define	PALT_TAG   MKTAG('P', 'A', 'L', 'T')
#define	SHOT_TAG   MKTAG('S', 'H', 'O', 'T')
#define	PALETTE_COUNT   256
#define	PALETTE_SIZE   (PALETTE_COUNT * 3)
#define	PALETTES_MAX   256

Functions
static av_cold int	xan_decode_end (AVCodecContext *avctx)
static av_cold int	xan_decode_init (AVCodecContext *avctx)
static int	xan_huffman_decode (uint8_t *dest, int dest_len, const uint8_t *src, int src_len)
static void	xan_unpack (uint8_t *dest, int dest_len, const uint8_t *src, int src_len)
	unpack simple compression
static void	xan_wc3_output_pixel_run (XanContext *s, AVFrame *frame, const uint8_t *pixel_buffer, int x, int y, int pixel_count)
static void	xan_wc3_copy_pixel_run (XanContext *s, AVFrame *frame, int x, int y, int pixel_count, int motion_x, int motion_y)
static int	xan_wc3_decode_frame (XanContext *s, AVFrame *frame)
static int	xan_decode_frame (AVCodecContext *avctx, AVFrame *frame, int *got_frame, AVPacket *avpkt)

Variables
static const uint8_t	gamma_lookup [256]
	This is a gamma correction that xan3 applies to all palette entries.
const FFCodec	ff_xan_wc3_decoder

Detailed Description

Xan video decoder for Wing Commander III computer game by Mario Brito (mbrit.nosp@m.o@st.nosp@m.udent.nosp@m..dei.nosp@m..uc.p.nosp@m.t) and Mike Melanson (melan.nosp@m.son@.nosp@m.pcisy.nosp@m.s.ne.nosp@m.t)

The xan_wc3 decoder outputs PAL8 data.

Definition in file xan.c.

Macro Definition Documentation

BITSTREAM_READER_LE

#define BITSTREAM_READER_LE

Definition at line 36 of file xan.c.

RUNTIME_GAMMA

#define RUNTIME_GAMMA   0

Definition at line 43 of file xan.c.

VGA__TAG

#define VGA__TAG   MKTAG('V', 'G', 'A', ' ')

Definition at line 45 of file xan.c.

Referenced by wc3_read_packet(), and xan_decode_frame().

PALT_TAG

#define PALT_TAG   MKTAG('P', 'A', 'L', 'T')

Definition at line 46 of file xan.c.

Referenced by wc3_read_header(), and xan_decode_frame().

SHOT_TAG

#define SHOT_TAG   MKTAG('S', 'H', 'O', 'T')

Definition at line 47 of file xan.c.

Referenced by wc3_read_packet(), and xan_decode_frame().

PALETTE_COUNT

#define PALETTE_COUNT   256

Definition at line 48 of file xan.c.

PALETTE_SIZE

#define PALETTE_SIZE   (PALETTE_COUNT * 3)

Definition at line 49 of file xan.c.

PALETTES_MAX

#define PALETTES_MAX   256

Definition at line 50 of file xan.c.

Referenced by xan_decode_frame().

Function Documentation

xan_decode_end()

static av_cold int xan_decode_end ( AVCodecContext * avctx )

static

Definition at line 74 of file xan.c.

xan_decode_init()

static av_cold int xan_decode_init ( AVCodecContext * avctx )

static

Definition at line 87 of file xan.c.

xan_huffman_decode()

static int xan_huffman_decode ( uint8_t * dest, int dest_len, const uint8_t * src, int src_len )

static

Definition at line 112 of file xan.c.

Referenced by xan_wc3_decode_frame().

xan_unpack()

static void xan_unpack ( uint8_t * dest, int dest_len, const uint8_t * src, int src_len )

static

unpack simple compression

Parameters

dest	destination buffer of dest_len, must be padded with at least 130 bytes

Definition at line 153 of file xan.c.

Referenced by xan_wc3_decode_frame().

xan_wc3_output_pixel_run()

static void xan_wc3_output_pixel_run ( XanContext * s, AVFrame * frame, const uint8_t * pixel_buffer, int x, int y, int pixel_count )

inlinestatic

Definition at line 207 of file xan.c.

Referenced by xan_wc3_decode_frame().

xan_wc3_copy_pixel_run()

static void xan_wc3_copy_pixel_run ( XanContext * s, AVFrame * frame, int x, int y, int pixel_count, int motion_x, int motion_y )

inlinestatic

Definition at line 237 of file xan.c.

Referenced by xan_wc3_decode_frame().

xan_wc3_decode_frame()

static int xan_wc3_decode_frame ( XanContext * s, AVFrame * frame )

static

Definition at line 295 of file xan.c.

Referenced by xan_decode_frame().

xan_decode_frame()

static int xan_decode_frame ( AVCodecContext * avctx, AVFrame * frame, int * got_frame, AVPacket * avpkt )

static

Definition at line 539 of file xan.c.

Variable Documentation

gamma_lookup

const uint8_t gamma_lookup[256]

static

This is a gamma correction that xan3 applies to all palette entries.

There is a peculiarity, namely that the values are clamped to 253 - it seems likely that this table was calculated by a buggy fixed-point implementation, the one above under RUNTIME_GAMMA behaves like this for example. The exponent value of 0.8 can be explained by this as well, since 0.8 = 4/5 and thus pow(x, 0.8) is still easy to calculate. Also, the input values are first rotated to the left by 2.

Definition at line 503 of file xan.c.

Referenced by xan_decode_frame().

ff_xan_wc3_decoder

const FFCodec ff_xan_wc3_decoder

Initial value:

= {
    .p.name         = "xan_wc3",
    CODEC_LONG_NAME("Wing Commander III / Xan"),
    .p.type         = AVMEDIA_TYPE_VIDEO,
    .p.id           = AV_CODEC_ID_XAN_WC3,
    .priv_data_size = sizeof(XanContext),
    .init           = xan_decode_init,
    .close          = xan_decode_end,
    FF_CODEC_DECODE_CB(xan_decode_frame),
    .p.capabilities = AV_CODEC_CAP_DR1,
    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
}

Definition at line 637 of file xan.c.