vmdav.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/*
 * Sierra VMD Audio & Video Decoders
 * Copyright (C) 2004 the ffmpeg project
 *
 * 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 vmdvideo.c
 * Sierra VMD audio & video decoders
 * by Vladimir "VAG" Gneushev (vagsoft at mail.ru)
 * for more information on the Sierra VMD format, visit:
 *   http://www.pcisys.net/~melanson/codecs/
 *
 * The video decoder outputs PAL8 colorspace data. The decoder expects
 * a 0x330-byte VMD file header to be transmitted via extradata during
 * codec initialization. Each encoded frame that is sent to this decoder
 * is expected to be prepended with the appropriate 16-byte frame
 * information record from the VMD file.
 *
 * The audio decoder, like the video decoder, expects each encoded data
 * chunk to be prepended with the appropriate 16-byte frame information
 * record from the VMD file. It does not require the 0x330-byte VMD file
 * header, but it does need the audio setup parameters passed in through
 * normal libavcodec API means.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "avcodec.h"
#include "dsputil.h"

#define VMD_HEADER_SIZE 0x330
#define PALETTE_COUNT 256

/*
 * Video Decoder
 */

typedef struct VmdVideoContext {

    AVCodecContext *avctx;
    DSPContext dsp;
    AVFrame frame;
    AVFrame prev_frame;

    unsigned char *buf;
    int size;

    unsigned char palette[PALETTE_COUNT * 4];
    unsigned char *unpack_buffer;
    int unpack_buffer_size;

    int x_off, y_off;
} VmdVideoContext;

#define QUEUE_SIZE 0x1000
#define QUEUE_MASK 0x0FFF

static void lz_unpack(unsigned char *src, unsigned char *dest, int dest_len)
{
    unsigned char *s;
    unsigned char *d;
    unsigned char *d_end;
    unsigned char queue[QUEUE_SIZE];
    unsigned int qpos;
    unsigned int dataleft;
    unsigned int chainofs;
    unsigned int chainlen;
    unsigned int speclen;
    unsigned char tag;
    unsigned int i, j;

    s = src;
    d = dest;
    d_end = d + dest_len;
    dataleft = AV_RL32(s);
    s += 4;
    memset(queue, 0x20, QUEUE_SIZE);
    if (AV_RL32(s) == 0x56781234) {
        s += 4;
        qpos = 0x111;
        speclen = 0xF + 3;
    } else {
        qpos = 0xFEE;
        speclen = 100;  /* no speclen */
    }

    while (dataleft > 0) {
        tag = *s++;
        if ((tag == 0xFF) && (dataleft > 8)) {
            if (d + 8 > d_end)
                return;
            for (i = 0; i < 8; i++) {
                queue[qpos++] = *d++ = *s++;
                qpos &= QUEUE_MASK;
            }
            dataleft -= 8;
        } else {
            for (i = 0; i < 8; i++) {
                if (dataleft == 0)
                    break;
                if (tag & 0x01) {
                    if (d + 1 > d_end)
                        return;
                    queue[qpos++] = *d++ = *s++;
                    qpos &= QUEUE_MASK;
                    dataleft--;
                } else {
                    chainofs = *s++;
                    chainofs |= ((*s & 0xF0) << 4);
                    chainlen = (*s++ & 0x0F) + 3;
                    if (chainlen == speclen)
                        chainlen = *s++ + 0xF + 3;
                    if (d + chainlen > d_end)
                        return;
                    for (j = 0; j < chainlen; j++) {
                        *d = queue[chainofs++ & QUEUE_MASK];
                        queue[qpos++] = *d++;
                        qpos &= QUEUE_MASK;
                    }
                    dataleft -= chainlen;
                }
                tag >>= 1;
            }
        }
    }
}

static int rle_unpack(unsigned char *src, unsigned char *dest,
    int src_len, int dest_len)
{
    unsigned char *ps;
    unsigned char *pd;
    int i, l;
    unsigned char *dest_end = dest + dest_len;

    ps = src;
    pd = dest;
    if (src_len & 1)
        *pd++ = *ps++;

    src_len >>= 1;
    i = 0;
    do {
        l = *ps++;
        if (l & 0x80) {
            l = (l & 0x7F) * 2;
            if (pd + l > dest_end)
                return (ps - src);
            memcpy(pd, ps, l);
            ps += l;
            pd += l;
        } else {
            if (pd + i > dest_end)
                return (ps - src);
            for (i = 0; i < l; i++) {
                *pd++ = ps[0];
                *pd++ = ps[1];
            }
            ps += 2;
        }
        i += l;
    } while (i < src_len);

    return (ps - src);
}

static void vmd_decode(VmdVideoContext *s)
{
    int i;
    unsigned int *palette32;
    unsigned char r, g, b;

    /* point to the start of the encoded data */
    unsigned char *p = s->buf + 16;

    unsigned char *pb;
    unsigned char meth;
    unsigned char *dp;   /* pointer to current frame */
    unsigned char *pp;   /* pointer to previous frame */
    unsigned char len;
    int ofs;

    int frame_x, frame_y;
    int frame_width, frame_height;
    int dp_size;

    frame_x = AV_RL16(&s->buf[6]);
    frame_y = AV_RL16(&s->buf[8]);
    frame_width = AV_RL16(&s->buf[10]) - frame_x + 1;
    frame_height = AV_RL16(&s->buf[12]) - frame_y + 1;

    if ((frame_width == s->avctx->width && frame_height == s->avctx->height) &&
        (frame_x || frame_y)) {

        s->x_off = frame_x;
        s->y_off = frame_y;
    }
    frame_x -= s->x_off;
    frame_y -= s->y_off;

    /* if only a certain region will be updated, copy the entire previous
     * frame before the decode */
    if (frame_x || frame_y || (frame_width != s->avctx->width) ||
        (frame_height != s->avctx->height)) {

        memcpy(s->frame.data[0], s->prev_frame.data[0],
            s->avctx->height * s->frame.linesize[0]);
    }

    /* check if there is a new palette */
    if (s->buf[15] & 0x02) {
        p += 2;
        palette32 = (unsigned int *)s->palette;
        for (i = 0; i < PALETTE_COUNT; i++) {
            r = *p++ * 4;
            g = *p++ * 4;
            b = *p++ * 4;
            palette32[i] = (r << 16) | (g << 8) | (b);
        }
        s->size -= (256 * 3 + 2);
    }
    if (s->size >= 0) {
        /* originally UnpackFrame in VAG's code */
        pb = p;
        meth = *pb++;
        if (meth & 0x80) {
            lz_unpack(pb, s->unpack_buffer, s->unpack_buffer_size);
            meth &= 0x7F;
            pb = s->unpack_buffer;
        }

        dp = &s->frame.data[0][frame_y * s->frame.linesize[0] + frame_x];
        dp_size = s->frame.linesize[0] * s->avctx->height;
        pp = &s->prev_frame.data[0][frame_y * s->prev_frame.linesize[0] + frame_x];
        switch (meth) {
        case 1:
            for (i = 0; i < frame_height; i++) {
                ofs = 0;
                do {
                    len = *pb++;
                    if (len & 0x80) {
                        len = (len & 0x7F) + 1;
                        if (ofs + len > frame_width)
                            return;
                        memcpy(&dp[ofs], pb, len);
                        pb += len;
                        ofs += len;
                    } else {
                        /* interframe pixel copy */
                        if (ofs + len + 1 > frame_width)
                            return;
                        memcpy(&dp[ofs], &pp[ofs], len + 1);
                        ofs += len + 1;
                    }
                } while (ofs < frame_width);
                if (ofs > frame_width) {
                    av_log(s->avctx, AV_LOG_ERROR, "VMD video: offset > width (%d > %d)\n",
                        ofs, frame_width);
                    break;
                }
                dp += s->frame.linesize[0];
                pp += s->prev_frame.linesize[0];
            }
            break;

        case 2:
            for (i = 0; i < frame_height; i++) {
                memcpy(dp, pb, frame_width);
                pb += frame_width;
                dp += s->frame.linesize[0];
                pp += s->prev_frame.linesize[0];