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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); \
}
const char * s
Definition: avisynth_c.h:631
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
#define av_log(a,...)
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
GLsizei count
Definition: opengl_enc.c:109
return

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); \
}
const char * s
Definition: avisynth_c.h:631
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
#define av_log(a,...)
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
GLsizei count
Definition: opengl_enc.c:109
return

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 608 of file vqavideo.c.

static av_cold int vqa_decode_end ( AVCodecContext avctx)
static

Definition at line 633 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"),
.priv_data_size = sizeof(VqaContext),
.close = vqa_decode_end,
.capabilities = AV_CODEC_CAP_DR1,
}
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:35
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:176
static int decode(AVCodecContext *avctx, void *data, int *got_sub, AVPacket *avpkt)
Definition: ccaption_dec.c:722
static av_cold int vqa_decode_end(AVCodecContext *avctx)
Definition: vqavideo.c:633
static int vqa_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
Definition: vqavideo.c:608
static av_cold int vqa_decode_init(AVCodecContext *avctx)
Definition: vqavideo.c:121
#define AV_CODEC_CAP_DR1
Codec uses get_buffer() for allocating buffers and supports custom allocators.
Definition: avcodec.h:953

Definition at line 644 of file vqavideo.c.