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

            }
            break;

        case 3:
            for (i = 0; i < frame_height; i++) {
                ofs = 0;
                do {
                    len = *pb++;
                    if (len & 0x80) {
                        len = (len & 0x7F) + 1;
                        if (*pb++ == 0xFF)
                            len = rle_unpack(pb, &dp[ofs], len, frame_width - ofs);
                        else
                            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);
                }
                dp += s->frame.linesize[0];
                pp += s->prev_frame.linesize[0];
            }
            break;
        }
    }
}

static int vmdvideo_decode_init(AVCodecContext *avctx)
{
    VmdVideoContext *s = avctx->priv_data;
    int i;
    unsigned int *palette32;
    int palette_index = 0;
    unsigned char r, g, b;
    unsigned char *vmd_header;
    unsigned char *raw_palette;

    s->avctx = avctx;
    avctx->pix_fmt = PIX_FMT_PAL8;
    dsputil_init(&s->dsp, avctx);

    /* make sure the VMD header made it */
    if (s->avctx->extradata_size != VMD_HEADER_SIZE) {
        av_log(s->avctx, AV_LOG_ERROR, "VMD video: expected extradata size of %d\n",
            VMD_HEADER_SIZE);
        return -1;
    }
    vmd_header = (unsigned char *)avctx->extradata;

    s->unpack_buffer_size = AV_RL32(&vmd_header[800]);
    s->unpack_buffer = av_malloc(s->unpack_buffer_size);
    if (!s->unpack_buffer)
        return -1;

    /* load up the initial palette */
    raw_palette = &vmd_header[28];
    palette32 = (unsigned int *)s->palette;
    for (i = 0; i < PALETTE_COUNT; i++) {
        r = raw_palette[palette_index++] * 4;
        g = raw_palette[palette_index++] * 4;
        b = raw_palette[palette_index++] * 4;
        palette32[i] = (r << 16) | (g << 8) | (b);
    }

    s->frame.data[0] = s->prev_frame.data[0] = NULL;

    return 0;
}

static int vmdvideo_decode_frame(AVCodecContext *avctx,
                                 void *data, int *data_size,
                                 uint8_t *buf, int buf_size)
{
    VmdVideoContext *s = avctx->priv_data;

    s->buf = buf;
    s->size = buf_size;

    if (buf_size < 16)
        return buf_size;

    s->frame.reference = 1;
    if (avctx->get_buffer(avctx, &s->frame)) {
        av_log(s->avctx, AV_LOG_ERROR, "VMD Video: get_buffer() failed\n");
        return -1;
    }

    vmd_decode(s);

    /* make the palette available on the way out */
    memcpy(s->frame.data[1], s->palette, PALETTE_COUNT * 4);

    /* shuffle frames */
    FFSWAP(AVFrame, s->frame, s->prev_frame);
    if (s->frame.data[0])
        avctx->release_buffer(avctx, &s->frame);

    *data_size = sizeof(AVFrame);
    *(AVFrame*)data = s->prev_frame;

    /* report that the buffer was completely consumed */
    return buf_size;
}

static int vmdvideo_decode_end(AVCodecContext *avctx)
{
    VmdVideoContext *s = avctx->priv_data;

    if (s->prev_frame.data[0])
        avctx->release_buffer(avctx, &s->prev_frame);
    av_free(s->unpack_buffer);

    return 0;
}


/*
 * Audio Decoder
 */

typedef struct VmdAudioContext {
    AVCodecContext *avctx;
    int channels;
    int bits;
    int block_align;
    int predictors[2];
} VmdAudioContext;

static uint16_t vmdaudio_table[128] = {
    0x000, 0x008, 0x010, 0x020, 0x030, 0x040, 0x050, 0x060, 0x070, 0x080,
    0x090, 0x0A0, 0x0B0, 0x0C0, 0x0D0, 0x0E0, 0x0F0, 0x100, 0x110, 0x120,
    0x130, 0x140, 0x150, 0x160, 0x170, 0x180, 0x190, 0x1A0, 0x1B0, 0x1C0,
    0x1D0, 0x1E0, 0x1F0, 0x200, 0x208, 0x210, 0x218, 0x220, 0x228, 0x230,
    0x238, 0x240, 0x248, 0x250, 0x258, 0x260, 0x268, 0x270, 0x278, 0x280,
    0x288, 0x290, 0x298, 0x2A0, 0x2A8, 0x2B0, 0x2B8, 0x2C0, 0x2C8, 0x2D0,
    0x2D8, 0x2E0, 0x2E8, 0x2F0, 0x2F8, 0x300, 0x308, 0x310, 0x318, 0x320,
    0x328, 0x330, 0x338, 0x340, 0x348, 0x350, 0x358, 0x360, 0x368, 0x370,
    0x378, 0x380, 0x388, 0x390, 0x398, 0x3A0, 0x3A8, 0x3B0, 0x3B8, 0x3C0,
    0x3C8, 0x3D0, 0x3D8, 0x3E0, 0x3E8, 0x3F0, 0x3F8, 0x400, 0x440, 0x480,
    0x4C0, 0x500, 0x540, 0x580, 0x5C0, 0x600, 0x640, 0x680, 0x6C0, 0x700,
    0x740, 0x780, 0x7C0, 0x800, 0x900, 0xA00, 0xB00, 0xC00, 0xD00, 0xE00,
    0xF00, 0x1000, 0x1400, 0x1800, 0x1C00, 0x2000, 0x3000, 0x4000
};

static int vmdaudio_decode_init(AVCodecContext *avctx)
{
    VmdAudioContext *s = avctx->priv_data;

    s->avctx = avctx;
    s->channels = avctx->channels;
    s->bits = avctx->bits_per_sample;
    s->block_align = avctx->block_align;

    av_log(s->avctx, AV_LOG_DEBUG, "%d channels, %d bits/sample, block align = %d, sample rate = %d\n",
            s->channels, s->bits, s->block_align, avctx->sample_rate);

    return 0;
}

static void vmdaudio_decode_audio(VmdAudioContext *s, unsigned char *data,
    uint8_t *buf, int stereo)
{
    int i;
    int chan = 0;
    int16_t *out = (int16_t*)data;

    for(i = 0; i < s->block_align; i++) {
        if(buf[i] & 0x80)
            s->predictors[chan] -= vmdaudio_table[buf[i] & 0x7F];
        else
            s->predictors[chan] += vmdaudio_table[buf[i]];
        s->predictors[chan] = av_clip_int16(s->predictors[chan]);
        out[i] = s->predictors[chan];
        chan ^= stereo;
    }
}

static int vmdaudio_loadsound(VmdAudioContext *s, unsigned char *data,
    uint8_t *buf, int silence)
{
    int bytes_decoded = 0;
    int i;

//    if (silence)
//        av_log(s->avctx, AV_LOG_INFO, "silent block!\n");
    if (s->channels == 2) {

        /* stereo handling */
        if (silence) {
            memset(data, 0, s->block_align * 2);
        } else {
            if (s->bits == 16)
                vmdaudio_decode_audio(s, data, buf, 1);
            else {
                /* copy the data but convert it to signed */
                for (i = 0; i < s->block_align; i++){
                    *data++ = buf[i] + 0x80;
                    *data++ = buf[i] + 0x80;
                }
            }
        }
    } else {
        bytes_decoded = s->block_align * 2;

        /* mono handling */
        if (silence) {
            memset(data, 0, s->block_align * 2);
        } else {
            if (s->bits == 16) {
                vmdaudio_decode_audio(s, data, buf, 0);
            } else {
                /* copy the data but convert it to signed */
                for (i = 0; i < s->block_align; i++){
                    *data++ = buf[i] + 0x80;
                    *data++ = buf[i] + 0x80;
                }
            }
        }
    }

    return s->block_align * 2;
}

static int vmdaudio_decode_frame(AVCodecContext *avctx,
                                 void *data, int *data_size,
                                 uint8_t *buf, int buf_size)
{
    VmdAudioContext *s = avctx->priv_data;
    unsigned char *output_samples = (unsigned char *)data;

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

    if (buf_size < 16)
        return buf_size;

    if (buf[6] == 1) {
        /* the chunk contains audio */
        *data_size = vmdaudio_loadsound(s, output_samples, p, 0);
    } else if (buf[6] == 2) {
        /* the chunk may contain audio */
        p += 4;
        *data_size = vmdaudio_loadsound(s, output_samples, p, (buf_size == 16));
        output_samples += (s->block_align * s->bits / 8);
    } else if (buf[6] == 3) {
        /* silent chunk */
        *data_size = vmdaudio_loadsound(s, output_samples, p, 1);
    }

    return buf_size;
}


/*
 * Public Data Structures
 */

AVCodec vmdvideo_decoder = {
    "vmdvideo",
    CODEC_TYPE_VIDEO,
    CODEC_ID_VMDVIDEO,
    sizeof(VmdVideoContext),
    vmdvideo_decode_init,
    NULL,
    vmdvideo_decode_end,
    vmdvideo_decode_frame,
    CODEC_CAP_DR1,
};

AVCodec vmdaudio_decoder = {
    "vmdaudio",
    CODEC_TYPE_AUDIO,
    CODEC_ID_VMDAUDIO,
    sizeof(VmdAudioContext),
    vmdaudio_decode_init,
    NULL,
    NULL,
    vmdaudio_decode_frame,
};