vqavideo.c File Reference

VQA Video Decoder. More...

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

Go to the source code of this file.

Data Structures
struct	VqaContext

Macros
#define	PALETTE_COUNT   256
#define	VQA_HEADER_SIZE   0x2A
#define	MAX_CODEBOOK_VECTORS   0xFF00
#define	SOLID_PIXEL_VECTORS   0x100
#define	MAX_VECTORS   (MAX_CODEBOOK_VECTORS + SOLID_PIXEL_VECTORS)
#define	MAX_CODEBOOK_SIZE   (MAX_VECTORS * 4 * 4)
#define	CBF0_TAG   MKBETAG('C', 'B', 'F', '0')
#define	CBFZ_TAG   MKBETAG('C', 'B', 'F', 'Z')
#define	CBP0_TAG   MKBETAG('C', 'B', 'P', '0')
#define	CBPZ_TAG   MKBETAG('C', 'B', 'P', 'Z')
#define	CPL0_TAG   MKBETAG('C', 'P', 'L', '0')
#define	CPLZ_TAG   MKBETAG('C', 'P', 'L', 'Z')
#define	VPTZ_TAG   MKBETAG('V', 'P', 'T', 'Z')
#define	CHECK_COUNT()
#define	CHECK_COPY(idx)

Functions
static av_cold int	vqa_decode_init (AVCodecContext *avctx)
static int	decode_format80 (VqaContext *s, int src_size, unsigned char *dest, int dest_size, int check_size)
static int	vqa_decode_chunk (VqaContext *s, AVFrame *frame)
static int	vqa_decode_frame (AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
static av_cold int	vqa_decode_end (AVCodecContext *avctx)

Variables
AVCodec	ff_vqa_decoder

Detailed Description

VQA Video Decoder.

Author

Mike Melanson (melan.nosp@m.son@.nosp@m.pcisy.nosp@m.s.ne.nosp@m.t)

See Also

http://wiki.multimedia.cx/index.php?title=VQA

The VQA video decoder outputs PAL8 or RGB555 colorspace data, depending on the type of data in the file.

This decoder needs the 42-byte VQHD header from the beginning of the VQA file passed through the extradata field. The VQHD header is laid out as:

bytes 0-3 chunk fourcc: 'VQHD' bytes 4-7 chunk size in big-endian format, should be 0x0000002A bytes 8-49 VQHD chunk data

Bytes 8-49 are what this decoder expects to see.

Briefly, VQA is a vector quantized animation format that operates in a VGA palettized colorspace. It operates on pixel vectors (blocks) of either 4x2 or 4x4 in size. Compressed VQA chunks can contain vector codebooks, palette information, and code maps for rendering vectors onto frames. Any of these components can also be compressed with a run-length encoding (RLE) algorithm commonly referred to as "format80".

VQA takes a novel approach to rate control. Each group of n frames (usually, n = 8) relies on a different vector codebook. Rather than transporting an entire codebook every 8th frame, the new codebook is broken up into 8 pieces and sent along with the compressed video chunks for each of the 8 frames preceding the 8 frames which require the codebook. A full codebook is also sent on the very first frame of a file. This is an interesting technique, although it makes random file seeking difficult despite the fact that the frames are all intracoded.

V1,2 VQA uses 12-bit codebook indexes. If the 12-bit indexes were packed into bytes and then RLE compressed, bytewise, the results would be poor. That is why the coding method divides each index into 2 parts, the top 4 bits and the bottom 8 bits, then RL encodes the 4-bit pieces together and the 8-bit pieces together. If most of the vectors are clustered into one group of 256 vectors, most of the 4-bit index pieces should be the same.

Definition in file vqavideo.c.

Macro Definition Documentation

#define PALETTE_COUNT   256

Definition at line 76 of file vqavideo.c.

Referenced by vqa_decode_frame().

#define VQA_HEADER_SIZE   0x2A

Definition at line 77 of file vqavideo.c.

Referenced by vqa_decode_init().

#define MAX_CODEBOOK_VECTORS   0xFF00

Definition at line 81 of file vqavideo.c.

#define SOLID_PIXEL_VECTORS   0x100

Definition at line 82 of file vqavideo.c.

#define MAX_VECTORS   (MAX_CODEBOOK_VECTORS + SOLID_PIXEL_VECTORS)

Definition at line 83 of file vqavideo.c.

#define MAX_CODEBOOK_SIZE   (MAX_VECTORS * 4 * 4)

Definition at line 84 of file vqavideo.c.

Referenced by vqa_decode_chunk(), and vqa_decode_init().

#define CBF0_TAG   MKBETAG('C', 'B', 'F', '0')

Definition at line 86 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define CBFZ_TAG   MKBETAG('C', 'B', 'F', 'Z')

Definition at line 87 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define CBP0_TAG   MKBETAG('C', 'B', 'P', '0')

Definition at line 88 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define CBPZ_TAG   MKBETAG('C', 'B', 'P', 'Z')

Definition at line 89 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define CPL0_TAG   MKBETAG('C', 'P', 'L', '0')

Definition at line 90 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define CPLZ_TAG   MKBETAG('C', 'P', 'L', 'Z')

Definition at line 91 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define VPTZ_TAG   MKBETAG('V', 'P', 'T', 'Z')

Definition at line 92 of file vqavideo.c.

Referenced by vqa_decode_chunk().

#define CHECK_COUNT

(

)

Value:

if (dest_index + count > dest_size) { \
        av_log(s->avctx, AV_LOG_ERROR, "decode_format80 problem: next op would overflow dest_index\n"); \
        av_log(s->avctx, AV_LOG_ERROR, "current dest_index = %d, count = %d, dest_size = %d\n", \
            dest_index, count, dest_size); \
        return AVERROR_INVALIDDATA; \
    }

Definition at line 208 of file vqavideo.c.

Referenced by decode_format80().

#define CHECK_COPY

(

idx

)

Value:

if (idx < 0 || idx + count > dest_size) { \
        av_log(s->avctx, AV_LOG_ERROR, "decode_format80 problem: next op would overflow dest_index\n"); \
        av_log(s->avctx, AV_LOG_ERROR, "current src_pos = %d, count = %d, dest_size = %d\n", \
            src_pos, count, dest_size); \
        return AVERROR_INVALIDDATA; \
    }

Definition at line 216 of file vqavideo.c.

Referenced by decode_format80().

Function Documentation

static av_cold int vqa_decode_init ( AVCodecContext *  avctx )

static

Definition at line 121 of file vqavideo.c.

static int decode_format80 ( VqaContext *  s, int  src_size, unsigned char *  dest, int  dest_size, int  check_size  )

static

Definition at line 225 of file vqavideo.c.

Referenced by vqa_decode_chunk().

static int vqa_decode_chunk ( VqaContext *  s, AVFrame *  frame  )

static

Definition at line 321 of file vqavideo.c.

Referenced by vqa_decode_frame().

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

static

Definition at line 604 of file vqavideo.c.

static av_cold int vqa_decode_end ( AVCodecContext *  avctx )

static

Definition at line 629 of file vqavideo.c.

Variable Documentation

AVCodec ff_vqa_decoder

Initial value:

= {
    .name           = "vqavideo",
    .long_name      = NULL_IF_CONFIG_SMALL("Westwood Studios VQA (Vector Quantized Animation) video"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_WS_VQA,
    .priv_data_size = sizeof(VqaContext),
    .init           = vqa_decode_init,
    .close          = vqa_decode_end,
    .decode         = vqa_decode_frame,
    .capabilities   = AV_CODEC_CAP_DR1,
}

Definition at line 640 of file vqavideo.c.