vqavideo.c

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/*
 * Westwood Studios VQA Video Decoder
 * Copyright (c) 2003 Mike Melanson <melanson@pcisys.net>
 * Copyright (c) 2021 Pekka Väänänen <pekka.vaananen@iki.fi>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
/**
 * @file
 * VQA Video Decoder
 * @author Mike Melanson (melanson@pcisys.net)
 * @see 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.
 *
 * VQA3 introduces a 15-bit high color codebook, delta coding, replaces
 * the above "split byte" scheme with RLE compression, and extends the
 * "format80" compression with relative references. In VQA3 the whole
 * codebook is always updated as a whole without splitting it into pieces.
 */
 
#include <stdio.h>
#include <string.h>
 
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "avcodec.h"
#include "bytestream.h"
#include "codec_internal.h"
#include "decode.h"
 
#define PALETTE_COUNT 256
#define VQA_HEADER_SIZE 0x2A
 
/* allocate the maximum vector space, regardless of the file version:
 * (0xFF00 codebook vectors + 0x100 solid pixel vectors) * (4x4 pixels/block) */
#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 * sizeof(uint16_t))
 
#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 VPTR_TAG MKBETAG('V', 'P', 'T', 'R')
#define VPRZ_TAG MKBETAG('V', 'P', 'R', 'Z')
 
typedef struct VqaContext {
    AVFrame *frame;
    AVCodecContext *avctx;
    GetByteContext gb;
 
    uint32_t palette[PALETTE_COUNT];
 
    int width;   /* width of a frame */
    int height;   /* height of a frame */
    int vector_width;  /* width of individual vector */
    int vector_height;  /* height of individual vector */
    int vqa_version;  /* this should be either 1, 2 or 3 */
 
    unsigned char *codebook; /* the current codebook */
    int codebook_size;
    unsigned char *next_codebook_buffer; /* accumulator for next codebook */
    int next_codebook_buffer_index;
 
    unsigned char *decode_buffer;
    int decode_buffer_size;
 
    /* number of frames to go before replacing codebook */
    int partial_countdown;
    int partial_count;
} VqaContext;
 
static av_cold int vqa_decode_init(AVCodecContext *avctx)
{
    VqaContext *s = avctx->priv_data;
    int i, j, codebook_index, ret;
    int colors;
 
    s->avctx = avctx;
 
    /* make sure the extradata made it */
    if (s->avctx->extradata_size != VQA_HEADER_SIZE) {
        av_log(s->avctx, AV_LOG_ERROR, "expected extradata size of %d\n", VQA_HEADER_SIZE);
        return AVERROR(EINVAL);
    }
 
    /* load up the VQA parameters from the header */
    s->vqa_version = s->avctx->extradata[0];
 
    if (s->vqa_version < 1 || s->vqa_version > 3) {
        avpriv_request_sample(avctx, "VQA Version %i", s->vqa_version);
        return AVERROR_INVALIDDATA;
    }
 
    s->width = AV_RL16(&s->avctx->extradata[6]);
    s->height = AV_RL16(&s->avctx->extradata[8]);
    if ((ret = ff_set_dimensions(avctx, s->width, s->height)) < 0) {
        s->width= s->height= 0;
        return ret;
    }
    s->vector_width = s->avctx->extradata[10];
    s->vector_height = s->avctx->extradata[11];
    s->partial_count = s->partial_countdown = s->avctx->extradata[13];
 
    colors = (s->avctx->extradata[14] << 8) | s->avctx->extradata[15];
 
    if (colors > 0) {
        avctx->pix_fmt = AV_PIX_FMT_PAL8;
    } else {
        avctx->pix_fmt = AV_PIX_FMT_RGB555LE;
    }
 
    /* the vector dimensions have to meet very stringent requirements */
    if ((s->vector_width != 4) ||
        ((s->vector_height != 2) && (s->vector_height != 4))) {
        /* return without further initialization */
        return AVERROR_INVALIDDATA;
    }
 
    if (s->width % s->vector_width || s->height % s->vector_height) {
        av_log(avctx, AV_LOG_ERROR, "Image size not multiple of block size\n");
        return AVERROR_INVALIDDATA;
    }
 
    s->frame = av_frame_alloc();
    if (!s->frame)
        return AVERROR(ENOMEM);
 
    /* allocate codebooks */
    s->codebook_size = MAX_CODEBOOK_SIZE;
    s->codebook = av_malloc(s->codebook_size);
    if (!s->codebook)
        return AVERROR(ENOMEM);
    s->next_codebook_buffer = av_malloc(s->codebook_size);
    if (!s->next_codebook_buffer)
        return AVERROR(ENOMEM);
 
    /* allocate decode buffer */
    s->decode_buffer_size = (s->width / s->vector_width) *
        (s->height / s->vector_height) * 2;
    s->decode_buffer = av_mallocz(s->decode_buffer_size);
    if (!s->decode_buffer)
        return AVERROR(ENOMEM);
 
    /* initialize the solid-color vectors */
    if (s->vector_height == 4) {
        codebook_index = 0xFF00 * 16;
        for (i = 0; i < 256; i++)
            for (j = 0; j < 16; j++)
                s->codebook[codebook_index++] = i;
    } else {
        codebook_index = 0xF00 * 8;
        for (i = 0; i < 256; i++)
            for (j = 0; j < 8; j++)
                s->codebook[codebook_index++] = i;
    }
    s->next_codebook_buffer_index = 0;
 
    return 0;
}
 
#define CHECK_COUNT() \
    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; \
    }
 
#define CHECK_COPY(idx) \
    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; \
    }
 
 
static int decode_format80(VqaContext *s, int src_size,
    unsigned char *dest, int dest_size, int check_size) {
 
    int dest_index = 0;
    int count, opcode, start;
    int src_pos;
    unsigned char color;
    int i;
    int relative = 0;
 
    if (src_size < 0 || src_size > bytestream2_get_bytes_left(&s->gb)) {
        av_log(s->avctx, AV_LOG_ERROR, "Chunk size %d is out of range\n",
               src_size);
        return AVERROR_INVALIDDATA;
    }
 
    /* the "new" scheme makes references relative to destination pointer */
    if (bytestream2_peek_byte(&s->gb) == 0x00) {
        relative = 1;
        bytestream2_get_byte(&s->gb);
        ff_tlog(s->avctx, "found new format stream ");
    }
 
    start = bytestream2_tell(&s->gb);
    while (bytestream2_tell(&s->gb) - start < src_size) {
        opcode = bytestream2_get_byte(&s->gb);
        ff_tlog(s->avctx, "opcode %02X: ", opcode);
 
        /* 0x80 means that frame is finished */
        if (opcode == 0x80)
            break;
 
        if (dest_index >= dest_size) {
            av_log(s->avctx, AV_LOG_ERROR, "decode_format80 problem: dest_index (%d) exceeded dest_size (%d)\n",
                dest_index, dest_size);
            return AVERROR_INVALIDDATA;
        }
 
        if (opcode == 0xFF) {
 
            count   = bytestream2_get_le16(&s->gb);
            src_pos = bytestream2_get_le16(&s->gb);
            if (relative)
                src_pos = dest_index - src_pos;
            ff_tlog(s->avctx, "(1) copy %X bytes from pos %X\n", count, src_pos);
            CHECK_COUNT();
            CHECK_COPY(src_pos);
            for (i = 0; i < count; i++)
                dest[dest_index + i] = dest[src_pos + i];
            dest_index += count;
 
        } else if (opcode == 0xFE) {
 
            count = bytestream2_get_le16(&s->gb);
            color = bytestream2_get_byte(&s->gb);
            ff_tlog(s->avctx, "(2) set %X bytes to %02X\n", count, color);
            CHECK_COUNT();
            memset(&dest[dest_index], color, count);
            dest_index += count;
 
        } else if ((opcode & 0xC0) == 0xC0) {
 
            count = (opcode & 0x3F) + 3;
            src_pos = bytestream2_get_le16(&s->gb);
            if (relative)
                src_pos = dest_index - src_pos;
            ff_tlog(s->avctx, "(3) copy %X bytes from pos %X\n", count, src_pos);
            CHECK_COUNT();
            CHECK_COPY(src_pos);
            for (i = 0; i < count; i++)
                dest[dest_index + i] = dest[src_pos + i];
            dest_index += count;
 
        } else if (opcode > 0x80) {
 
            count = opcode & 0x3F;
            ff_tlog(s->avctx, "(4) copy %X bytes from source to dest\n", count);
            CHECK_COUNT();
            bytestream2_get_buffer(&s->gb, &dest[dest_index], count);
            dest_index += count;
 
        } else {
 
            count = ((opcode & 0x70) >> 4) + 3;
            src_pos = bytestream2_get_byte(&s->gb) | ((opcode & 0x0F) << 8);
            ff_tlog(s->avctx, "(5) copy %X bytes from relpos %X\n", count, src_pos);
            CHECK_COUNT();
            CHECK_COPY(dest_index - src_pos);
            for (i = 0; i < count; i++)
                dest[dest_index + i] = dest[dest_index - src_pos + i];
            dest_index += count;
        }
    }
 
    /* validate that the entire destination buffer was filled; this is
     * important for decoding frame maps since each vector needs to have a
     * codebook entry; it is not important for compressed codebooks because
     * not every entry needs to be filled */
    if (check_size)
        if (dest_index < dest_size) {
            av_log(s->avctx, AV_LOG_ERROR, "decode_format80 problem: decode finished with dest_index (%d) < dest_size (%d)\n",
                dest_index, dest_size);
            memset(dest + dest_index, 0, dest_size - dest_index);
        }
 
    return 0; // let's display what we decoded anyway
}
 
static int vqa_decode_frame_pal8(VqaContext *s, AVFrame *frame)
{
    unsigned int chunk_type;
    unsigned int chunk_size;
    int byte_skip;
    unsigned int index = 0;
    int i;
    unsigned char r, g, b;
    int index_shift;
    int res;
 
    int cbf0_chunk = -1;
    int cbfz_chunk = -1;
    int cbp0_chunk = -1;
    int cbpz_chunk = -1;
    int cpl0_chunk = -1;
    int cplz_chunk = -1;
    int vptz_chunk = -1;
 
    int x, y;
    int lines = 0;
    int pixel_ptr;
    int vector_index = 0;
    int lobyte = 0;
    int hibyte = 0;
    int lobytes = 0;
    int hibytes = s->decode_buffer_size / 2;
 
    /* first, traverse through the frame and find the subchunks */
    while (bytestream2_get_bytes_left(&s->gb) >= 8) {
 
        chunk_type = bytestream2_get_be32u(&s->gb);
        index      = bytestream2_tell(&s->gb);
        chunk_size = bytestream2_get_be32u(&s->gb);
 
        switch (chunk_type) {
 
        case CBF0_TAG:
            cbf0_chunk = index;
            break;
 
        case CBFZ_TAG:
            cbfz_chunk = index;
            break;
 
        case CBP0_TAG:
            cbp0_chunk = index;
            break;
 
        case CBPZ_TAG:
            cbpz_chunk = index;
            break;
 
        case CPL0_TAG:
            cpl0_chunk = index;
            break;
 
        case CPLZ_TAG:
            cplz_chunk = index;
            break;
 
        case VPTZ_TAG:
            vptz_chunk = index;
            break;
 
        default:
            av_log(s->avctx, AV_LOG_ERROR, "Found unknown chunk type: %s (%08X)\n",
                   av_fourcc2str(av_bswap32(chunk_type)), chunk_type);
            break;
        }
 
        byte_skip = chunk_size & 0x01;
        bytestream2_skip(&s->gb, chunk_size + byte_skip);
    }
 
    /* next, deal with the palette */
    if ((cpl0_chunk != -1) && (cplz_chunk != -1)) {
 
        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "problem: found both CPL0 and CPLZ chunks\n");
        return AVERROR_INVALIDDATA;
    }
 
    /* decompress the palette chunk */
    if (cplz_chunk != -1) {
 
/* yet to be handled */
 
    }
 
    /* convert the RGB palette into the machine's endian format */
    if (cpl0_chunk != -1) {
 
        bytestream2_seek(&s->gb, cpl0_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
        /* sanity check the palette size */
        if (chunk_size / 3 > 256 || chunk_size > bytestream2_get_bytes_left(&s->gb)) {
            av_log(s->avctx, AV_LOG_ERROR, "problem: found a palette chunk with %d colors\n",
                chunk_size / 3);
            return AVERROR_INVALIDDATA;
        }
        for (i = 0; i < chunk_size / 3; i++) {
            /* scale by 4 to transform 6-bit palette -> 8-bit */
            r = bytestream2_get_byteu(&s->gb) * 4;
            g = bytestream2_get_byteu(&s->gb) * 4;
            b = bytestream2_get_byteu(&s->gb) * 4;
            s->palette[i] = 0xFFU << 24 | r << 16 | g << 8 | b;
            s->palette[i] |= s->palette[i] >> 6 & 0x30303;
        }
    }
 
    /* next, look for a full codebook */
    if ((cbf0_chunk != -1) && (cbfz_chunk != -1)) {
 
        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "problem: found both CBF0 and CBFZ chunks\n");
        return AVERROR_INVALIDDATA;
    }
 
    /* decompress the full codebook chunk */
    if (cbfz_chunk != -1) {
 
        bytestream2_seek(&s->gb, cbfz_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
        if ((res = decode_format80(s, chunk_size, s->codebook,
                                   s->codebook_size, 0)) < 0)
            return res;
    }
 
    /* copy a full codebook */
    if (cbf0_chunk != -1) {
 
        bytestream2_seek(&s->gb, cbf0_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
        /* sanity check the full codebook size */
        if (chunk_size > MAX_CODEBOOK_SIZE) {
            av_log(s->avctx, AV_LOG_ERROR, "problem: CBF0 chunk too large (0x%X bytes)\n",
                chunk_size);
            return AVERROR_INVALIDDATA;
        }
 
        bytestream2_get_buffer(&s->gb, s->codebook, chunk_size);
    }
 
    /* decode the frame */
    if (vptz_chunk == -1) {
 
        /* something is wrong if there is no VPTZ chunk */
        av_log(s->avctx, AV_LOG_ERROR, "problem: no VPTZ chunk found\n");
        return AVERROR_INVALIDDATA;
    }
 
    bytestream2_seek(&s->gb, vptz_chunk, SEEK_SET);
    chunk_size = bytestream2_get_be32(&s->gb);
    if ((res = decode_format80(s, chunk_size,
                               s->decode_buffer, s->decode_buffer_size, 1)) < 0)
        return res;
 
    /* render the final PAL8 frame */
    if (s->vector_height == 4)
        index_shift = 4;
    else
        index_shift = 3;
    for (y = 0; y < s->height; y += s->vector_height) {
        for (x = 0; x < s->width; x += 4, lobytes++, hibytes++) {
            pixel_ptr = y * frame->linesize[0] + x;
 
            /* get the vector index, the method for which varies according to
             * VQA file version */
            switch (s->vqa_version) {
 
            case 1:
                lobyte = s->decode_buffer[lobytes * 2];
                hibyte = s->decode_buffer[(lobytes * 2) + 1];
                vector_index = ((hibyte << 8) | lobyte) >> 3;
                vector_index <<= index_shift;
                lines = s->vector_height;
                /* uniform color fill - a quick hack */
                if (hibyte == 0xFF) {
                    while (lines--) {
                        frame->data[0][pixel_ptr + 0] = 255 - lobyte;
                        frame->data[0][pixel_ptr + 1] = 255 - lobyte;
                        frame->data[0][pixel_ptr + 2] = 255 - lobyte;
                        frame->data[0][pixel_ptr + 3] = 255 - lobyte;
                        pixel_ptr += frame->linesize[0];
                    }
                    lines=0;
                }
                break;
 
            case 2:
                lobyte = s->decode_buffer[lobytes];
                hibyte = s->decode_buffer[hibytes];
                vector_index = (hibyte << 8) | lobyte;
                vector_index <<= index_shift;
                lines = s->vector_height;
                break;
 
            case 3:
                av_log(s->avctx, AV_LOG_ERROR, "VQA3 shouldn't have a color palette");
                return AVERROR_INVALIDDATA;
            }
 
            while (lines--) {
                frame->data[0][pixel_ptr + 0] = s->codebook[vector_index++];
                frame->data[0][pixel_ptr + 1] = s->codebook[vector_index++];
                frame->data[0][pixel_ptr + 2] = s->codebook[vector_index++];
                frame->data[0][pixel_ptr + 3] = s->codebook[vector_index++];
                pixel_ptr += frame->linesize[0];
            }
        }
    }
 
    /* handle partial codebook */
    if ((cbp0_chunk != -1) && (cbpz_chunk != -1)) {
        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "problem: found both CBP0 and CBPZ chunks\n");
        return AVERROR_INVALIDDATA;
    }
 
    if (cbp0_chunk != -1) {
 
        bytestream2_seek(&s->gb, cbp0_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
 
        if (chunk_size > MAX_CODEBOOK_SIZE - s->next_codebook_buffer_index) {
            av_log(s->avctx, AV_LOG_ERROR, "cbp0 chunk too large (%u bytes)\n",
                   chunk_size);
            return AVERROR_INVALIDDATA;
        }
 
        /* accumulate partial codebook */
        if (chunk_size != bytestream2_get_buffer(&s->gb, &s->next_codebook_buffer[s->next_codebook_buffer_index],
                               chunk_size))
            return AVERROR_INVALIDDATA;
        s->next_codebook_buffer_index += chunk_size;
 
        s->partial_countdown--;
        if (s->partial_countdown <= 0) {
 
            /* time to replace codebook */
            memcpy(s->codebook, s->next_codebook_buffer,
                s->next_codebook_buffer_index);
 
            /* reset accounting */
            s->next_codebook_buffer_index = 0;
            s->partial_countdown = s->partial_count;
        }
    }
 
    if (cbpz_chunk != -1) {
 
        bytestream2_seek(&s->gb, cbpz_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
 
        if (chunk_size > MAX_CODEBOOK_SIZE - s->next_codebook_buffer_index) {
            av_log(s->avctx, AV_LOG_ERROR, "cbpz chunk too large (%u bytes)\n",
                   chunk_size);
            return AVERROR_INVALIDDATA;
        }
 
        /* accumulate partial codebook */
        if (chunk_size != bytestream2_get_buffer(&s->gb, &s->next_codebook_buffer[s->next_codebook_buffer_index],
                               chunk_size))
            return AVERROR_INVALIDDATA;
        s->next_codebook_buffer_index += chunk_size;
 
        s->partial_countdown--;
        if (s->partial_countdown <= 0) {
            bytestream2_init(&s->gb, s->next_codebook_buffer, s->next_codebook_buffer_index);
            /* decompress codebook */
            res = decode_format80(s, s->next_codebook_buffer_index,
                                  s->codebook, s->codebook_size, 0);
 
            /* reset accounting */
            s->next_codebook_buffer_index = 0;
            s->partial_countdown = s->partial_count;
            if (res < 0)
                return res;
        }
    }
 
    return 0;
}
 
static int vqa_decode_frame_hicolor(VqaContext *s, AVFrame *frame)
{
    unsigned int chunk_type;
    unsigned int chunk_size;
    unsigned int index = 0;
    int res;
 
    int cbf0_chunk = -1;
    int cbfz_chunk = -1;
    int vptr_chunk = -1;
    int vprz_chunk = -1;
 
    GetByteContext gb_stream;
 
    while (bytestream2_get_bytes_left(&s->gb) >= 8) {
        chunk_type = bytestream2_get_be32u(&s->gb);
        index      = bytestream2_tell(&s->gb);
        chunk_size = bytestream2_get_be32u(&s->gb);
 
        switch (chunk_type) {
        case CBF0_TAG:
            cbf0_chunk = index;
            break;
        case CBFZ_TAG:
            cbfz_chunk = index;
            break;
        case VPTR_TAG:
            vptr_chunk = index;
            break;
        case VPRZ_TAG:
            vprz_chunk = index;
            break;
        default:
            av_log(s->avctx, AV_LOG_ERROR, "Found unknown chunk type: %s (%08X)\n",
                   av_fourcc2str(av_bswap32(chunk_type)), chunk_type);
            break;
        }
 
        bytestream2_skip(&s->gb, chunk_size + (chunk_size & 0x01));
    }
 
    /* next, look for a full codebook */
    if ((cbf0_chunk != -1) && (cbfz_chunk != -1)) {
        /* a chunk should not have both chunk types */
        av_log(s->avctx, AV_LOG_ERROR, "problem: found both CBF0 and CBFZ chunks\n");
        return AVERROR_INVALIDDATA;
    }
 
    /* decompress the full codebook chunk */
    if (cbfz_chunk != -1) {
        bytestream2_seek(&s->gb, cbfz_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
        if ((res = decode_format80(s, chunk_size, s->codebook,
                                   s->codebook_size, 0)) < 0)
            return res;
    }
 
    /* copy a full codebook */
    if (cbf0_chunk != -1) {
        bytestream2_seek(&s->gb, cbf0_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
        /* sanity check the full codebook size */
        if (chunk_size > MAX_CODEBOOK_SIZE) {
            av_log(s->avctx, AV_LOG_ERROR, "problem: CBF0 chunk too large (0x%X bytes)\n",
                chunk_size);
            return AVERROR_INVALIDDATA;
        }
 
        bytestream2_get_buffer(&s->gb, s->codebook, chunk_size);
    }
 
    /* decode the frame */
 
    if (vptr_chunk != -1) {
        /* copy uncompressed tile data */
        bytestream2_seek(&s->gb, vptr_chunk, SEEK_SET);
        chunk_size = bytestream2_get_be32(&s->gb);
        if (chunk_size > s->decode_buffer_size) {
            av_log(s->avctx, AV_LOG_ERROR, "VPTR chunk didn't fit in decode buffer");
            return AVERROR_INVALIDDATA;
        }
        bytestream2_get_buffer(&s->gb, s->decode_buffer, chunk_size);
    } else if (vprz_chunk != -1) {
        /* decompress the tile data */
        bytestream2_seek(&s->gb, vprz_chunk, SEEK_SET);
 
        chunk_size = bytestream2_get_be32(&s->gb);
        if ((res = decode_format80(s, chunk_size, s->decode_buffer, s->decode_buffer_size, 0)) < 0)
            return res;
    } else {
        av_log(s->avctx, AV_LOG_ERROR, "frame has no block data\n");
        return AVERROR_INVALIDDATA;
    }
 
    /* now uncompress the per-row RLE of the decode buffer and draw the blocks in framebuffer */
 
    bytestream2_init(&gb_stream, s->decode_buffer, s->decode_buffer_size);
 
    for (int y_pos = 0; y_pos < s->height; y_pos += s->vector_height) {
        int x_pos = 0;
 
        while (x_pos < s->width) {
            int vector_index = 0;
            int count = 0;
            uint16_t code;
            int type;
 
            if (bytestream2_get_bytes_left(&gb_stream) < 2)
                return AVERROR_INVALIDDATA;
 
            code = bytestream2_get_le16(&gb_stream);
 
            type = code >> 13;
            code &= 0x1fff;
 
            if (type == 0) {
                x_pos += 4 * code;
                continue;
            } else if (type < 3) {
                vector_index = code & 0xff;
                count = ((code & 0x1f00) >> 7) + 1 + type;
            } else if (type < 5) {
                vector_index = code;
                count = 1;
            } else if (type < 7) {
                vector_index = code;
                count = bytestream2_get_byte(&gb_stream);
            } else {
                av_log(s->avctx, AV_LOG_ERROR, " unknown type in VPTR chunk (%d)\n",type);
                return AVERROR_INVALIDDATA;
            }
 
            if (count < 0 || count > (s->width - x_pos) / s->vector_width) {
                av_log(s->avctx, AV_LOG_ERROR, "invalid count: %d\n", count);
                return AVERROR_INVALIDDATA;
            }
 
            while (count-- && x_pos < s->width) {
                const int bytes_per_vector = 4 * s->vector_height * sizeof(uint16_t);
                unsigned char *src = s->codebook + vector_index * bytes_per_vector;
                unsigned char *dst = s->frame->data[0] + y_pos * s->frame->linesize[0]
                    + sizeof(uint16_t) * x_pos;
 
                if (vector_index >= MAX_VECTORS)
                    return AVERROR_INVALIDDATA;
 
                for (int y = 0; y < s->vector_height; y++) {
                    int size = 4 * sizeof(uint16_t);
                    memcpy(dst, src, size);
                    dst += s->frame->linesize[0];
                    src += size;
                }
 
                /* we might want to read the next block index from stream */
                if ((type == 2) && count > 0) {
                    vector_index = bytestream2_get_byte(&gb_stream);
                }
 
                x_pos += 4;
            }
 
            if (count > 0) {
                av_log(s->avctx, AV_LOG_ERROR, "had %d leftover vectors\n", count);
                return AVERROR_BUG;
            }
        }
    }
 
    return 0;
}
 
static int vqa_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
                            int *got_frame, AVPacket *avpkt)
{
    VqaContext *s = avctx->priv_data;
    int res;
 
    if ((res = ff_reget_buffer(avctx, s->frame, 0)) < 0)
        return res;
 
    bytestream2_init(&s->gb, avpkt->data, avpkt->size);
 
    if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {
        if ((res = vqa_decode_frame_pal8(s, s->frame)) < 0)
            return res;
 
        /* make the palette available on the way out */
        memcpy(s->frame->data[1], s->palette, PALETTE_COUNT * 4);
    } else if (avctx->pix_fmt == AV_PIX_FMT_RGB555LE) {
        if ((res = vqa_decode_frame_hicolor(s, s->frame)) < 0)
            return res;
    } else {
        av_log(s->avctx, AV_LOG_ERROR, "unsupported pixel format\n");
        return AVERROR_BUG;
    }
 
    if ((res = av_frame_ref(rframe, s->frame)) < 0)
        return res;
 
    *got_frame      = 1;
 
    /* report that the buffer was completely consumed */
    return avpkt->size;
}
 
static av_cold int vqa_decode_end(AVCodecContext *avctx)
{
    VqaContext *s = avctx->priv_data;
 
    av_frame_free(&s->frame);
    av_freep(&s->codebook);
    av_freep(&s->next_codebook_buffer);
    av_freep(&s->decode_buffer);
 
    return 0;
}
 
static const FFCodecDefault vqa_defaults[] = {
    { "max_pixels", "640*480" },
    { NULL },
};
 
const FFCodec ff_vqa_decoder = {
    .p.name         = "vqavideo",
    CODEC_LONG_NAME("Westwood Studios VQA (Vector Quantized Animation) video"),
    .p.type         = AVMEDIA_TYPE_VIDEO,
    .p.id           = AV_CODEC_ID_WS_VQA,
    .priv_data_size = sizeof(VqaContext),
    .init           = vqa_decode_init,
    .close          = vqa_decode_end,
    FF_CODEC_DECODE_CB(vqa_decode_frame),
    .p.capabilities = AV_CODEC_CAP_DR1,
    .defaults       = vqa_defaults,
    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
};