libxvidff.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

    *p = *picture;

    /* Let XviD know where to put the frame. */
    xvid_enc_frame.bitstream = frame;
    xvid_enc_frame.length = buf_size;

    /* Initialize input image fields */
    if( avctx->pix_fmt != PIX_FMT_YUV420P ) {
        av_log(avctx, AV_LOG_ERROR, "XviD: Color spaces other than 420p not supported\n");
        return -1;
    }

    xvid_enc_frame.input.csp = XVID_CSP_PLANAR; /* YUV420P */

    for( i = 0; i < 4; i++ ) {
        xvid_enc_frame.input.plane[i] = picture->data[i];
        xvid_enc_frame.input.stride[i] = picture->linesize[i];
    }

    /* Encoder Flags */
    xvid_enc_frame.vop_flags = x->vop_flags;
    xvid_enc_frame.vol_flags = x->vol_flags;
    xvid_enc_frame.motion = x->me_flags;
    xvid_enc_frame.type = XVID_TYPE_AUTO;

    /* Quant Setting */
    if( x->qscale ) xvid_enc_frame.quant = picture->quality / FF_QP2LAMBDA;
    else xvid_enc_frame.quant = 0;

    /* Matrices */
    xvid_enc_frame.quant_intra_matrix = x->intra_matrix;
    xvid_enc_frame.quant_inter_matrix = x->inter_matrix;

    /* Encode */
    xerr = xvid_encore(x->encoder_handle, XVID_ENC_ENCODE,
        &xvid_enc_frame, &xvid_enc_stats);

    /* Two-pass log buffer swapping */
    avctx->stats_out = NULL;
    if( x->twopassbuffer ) {
        tmp = x->old_twopassbuffer;
        x->old_twopassbuffer = x->twopassbuffer;
        x->twopassbuffer = tmp;
        x->twopassbuffer[0] = 0;
        if( x->old_twopassbuffer[0] != 0 ) {
            avctx->stats_out = x->old_twopassbuffer;
        }
    }

    if( 0 <= xerr ) {
        p->quality = xvid_enc_stats.quant * FF_QP2LAMBDA;
        if( xvid_enc_stats.type == XVID_TYPE_PVOP )
            p->pict_type = FF_P_TYPE;
        else if( xvid_enc_stats.type == XVID_TYPE_BVOP )
            p->pict_type = FF_B_TYPE;
        else if( xvid_enc_stats.type == XVID_TYPE_SVOP )
            p->pict_type = FF_S_TYPE;
        else
            p->pict_type = FF_I_TYPE;
        if( xvid_enc_frame.out_flags & XVID_KEYFRAME ) {
            p->key_frame = 1;
            if( x->quicktime_format )
                return xvid_strip_vol_header(avctx, frame,
                    xvid_enc_stats.hlength, xerr);
         } else
            p->key_frame = 0;

        return xerr;
    } else {
        av_log(avctx, AV_LOG_ERROR, "XviD: Encoding Error Occurred: %i\n", xerr);
        return -1;
    }
}

/**
 * Destroys the private context for the encoder.
 * All buffers are freed, and the XviD encoder context is destroyed.
 *
 * @param avctx AVCodecContext pointer to context
 * @return Returns 0, success guaranteed
 */
int ff_xvid_encode_close(AVCodecContext *avctx) {
    xvid_context_t *x = avctx->priv_data;

    xvid_encore(x->encoder_handle, XVID_ENC_DESTROY, NULL, NULL);

    if( avctx->extradata != NULL )
        av_free(avctx->extradata);
    if( x->twopassbuffer != NULL ) {
        av_free(x->twopassbuffer);
        av_free(x->old_twopassbuffer);
    }
    if( x->twopassfile != NULL )
        av_free(x->twopassfile);
    if( x->intra_matrix != NULL )
        av_free(x->intra_matrix);
    if( x->inter_matrix != NULL )
        av_free(x->inter_matrix);

    return 0;
}

/**
 * Routine to create a global VO/VOL header for MP4 container.
 * What we do here is extract the header from the XviD bitstream
 * as it is encoded. We also strip the repeated headers from the
 * bitstream when a global header is requested for MPEG-4 ISO
 * compliance.
 *
 * @param avctx AVCodecContext pointer to context
 * @param frame Pointer to encoded frame data
 * @param header_len Length of header to search
 * @param frame_len Length of encoded frame data
 * @return Returns new length of frame data
 */
int xvid_strip_vol_header(AVCodecContext *avctx,
                  unsigned char *frame,
                  unsigned int header_len,
                  unsigned int frame_len) {
    int vo_len = 0, i;

    for( i = 0; i < header_len - 3; i++ ) {
        if( frame[i] == 0x00 &&
            frame[i+1] == 0x00 &&
            frame[i+2] == 0x01 &&
            frame[i+3] == 0xB6 ) {
            vo_len = i;
            break;
        }
    }

    if( vo_len > 0 ) {
        /* We need to store the header, so extract it */
        if( avctx->extradata == NULL ) {
            avctx->extradata = av_malloc(vo_len);
            memcpy(avctx->extradata, frame, vo_len);
            avctx->extradata_size = vo_len;
        }
        /* Less dangerous now, memmove properly copies the two
           chunks of overlapping data */
        memmove(frame, &(frame[vo_len]), frame_len - vo_len);
        return frame_len - vo_len;
    } else
        return frame_len;
}

/**
 * Routine to correct a possibly erroneous framerate being fed to us.
 * XviD currently chokes on framerates where the ticks per frame is
 * extremely large. This function works to correct problems in this area
 * by estimating a new framerate and taking the simpler fraction of
 * the two presented.
 *
 * @param avctx Context that contains the framerate to correct.
 */
void xvid_correct_framerate(AVCodecContext *avctx) {
    int frate, fbase;
    int est_frate, est_fbase;
    int gcd;
    float est_fps, fps;

    frate = avctx->time_base.den;
    fbase = avctx->time_base.num;

    gcd = ff_gcd(frate, fbase);
    if( gcd > 1 ) {
        frate /= gcd;
        fbase /= gcd;
    }

    if( frate <= 65000 && fbase <= 65000 ) {
        avctx->time_base.den = frate;
        avctx->time_base.num = fbase;
        return;
    }

    fps = (float)frate / (float)fbase;
    est_fps = roundf(fps * 1000.0) / 1000.0;

    est_frate = (int)est_fps;
    if( est_fps > (int)est_fps ) {
        est_frate = (est_frate + 1) * 1000;
        est_fbase = (int)roundf((float)est_frate / est_fps);
    } else
        est_fbase = 1;

    gcd = ff_gcd(est_frate, est_fbase);
    if( gcd > 1 ) {
        est_frate /= gcd;
        est_fbase /= gcd;
    }

    if( fbase > est_fbase ) {
        avctx->time_base.den = est_frate;
        avctx->time_base.num = est_fbase;
        av_log(avctx, AV_LOG_DEBUG,
            "XviD: framerate re-estimated: %.2f, %.3f%% correction\n",
            est_fps, (((est_fps - fps)/fps) * 100.0));
    } else {
        avctx->time_base.den = frate;
        avctx->time_base.num = fbase;
    }
}

/*
 * XviD 2-Pass Kludge Section
 *
 * XviD's default 2-pass doesn't allow us to create data as we need to, so
 * this section spends time replacing the first pass plugin so we can write
 * statistic information as libavcodec requests in. We have another kludge
 * that allows us to pass data to the second pass in XviD without a custom
 * rate-control plugin.
 */

/**
 * Initializes the two-pass plugin and context.
 *
 * @param param Input construction parameter structure
 * @param handle Private context handle
 * @return Returns XVID_ERR_xxxx on failure, or 0 on success.
 */
static int xvid_ff_2pass_create(xvid_plg_create_t * param,
                                void ** handle) {
    xvid_ff_pass1_t *x = (xvid_ff_pass1_t *)param->param;
    char *log = x->context->twopassbuffer;

    /* Do a quick bounds check */
    if( log == NULL )
        return XVID_ERR_FAIL;

    /* We use snprintf() */
    /* This is because we can safely prevent a buffer overflow */
    log[0] = 0;
    snprintf(log, BUFFER_REMAINING(log),
        "# ffmpeg 2-pass log file, using xvid codec\n");
    snprintf(BUFFER_CAT(log), BUFFER_REMAINING(log),
        "# Do not modify. libxvidcore version: %d.%d.%d\n\n",
        XVID_VERSION_MAJOR(XVID_VERSION),
        XVID_VERSION_MINOR(XVID_VERSION),
        XVID_VERSION_PATCH(XVID_VERSION));

    *handle = x->context;
    return 0;
}

/**
 * Destroys the two-pass plugin context.
 *
 * @param ref Context pointer for the plugin
 * @param param Destrooy context
 * @return Returns 0, success guaranteed
 */
static int xvid_ff_2pass_destroy(xvid_context_t *ref,
                                xvid_plg_destroy_t *param) {
    /* Currently cannot think of anything to do on destruction */
    /* Still, the framework should be here for reference/use */
    if( ref->twopassbuffer != NULL )
        ref->twopassbuffer[0] = 0;
    return 0;
}

/**
 * Enables fast encode mode during the first pass.
 *
 * @param ref Context pointer for the plugin
 * @param param Frame data
 * @return Returns 0, success guaranteed
 */
static int xvid_ff_2pass_before(xvid_context_t *ref,
                                xvid_plg_data_t *param) {
    int motion_remove;
    int motion_replacements;
    int vop_remove;

    /* Nothing to do here, result is changed too much */
    if( param->zone && param->zone->mode == XVID_ZONE_QUANT )
        return 0;

    /* We can implement a 'turbo' first pass mode here */
    param->quant = 2;

    /* Init values */
    motion_remove = ~XVID_ME_CHROMA_PVOP &
                    ~XVID_ME_CHROMA_BVOP &
                    ~XVID_ME_EXTSEARCH16 &
                    ~XVID_ME_ADVANCEDDIAMOND16;
    motion_replacements = XVID_ME_FAST_MODEINTERPOLATE |
                          XVID_ME_SKIP_DELTASEARCH |
                          XVID_ME_FASTREFINE16 |
                          XVID_ME_BFRAME_EARLYSTOP;
    vop_remove = ~XVID_VOP_MODEDECISION_RD &
                 ~XVID_VOP_FAST_MODEDECISION_RD &
                 ~XVID_VOP_TRELLISQUANT &
                 ~XVID_VOP_INTER4V &
                 ~XVID_VOP_HQACPRED;

    param->vol_flags &= ~XVID_VOL_GMC;
    param->vop_flags &= vop_remove;
    param->motion_flags &= motion_remove;
    param->motion_flags |= motion_replacements;

    return 0;
}

/**
 * Captures statistic data and writes it during first pass.
 *
 * @param ref Context pointer for the plugin
 * @param param Statistic data
 * @return Returns XVID_ERR_xxxx on failure, or 0 on success
 */
static int xvid_ff_2pass_after(xvid_context_t *ref,
                                xvid_plg_data_t *param) {
    char *log = ref->twopassbuffer;
    char *frame_types = " ipbs";
    char frame_type;

    /* Quick bounds check */
    if( log == NULL )
        return XVID_ERR_FAIL;

    /* Convert the type given to us into a character */
    if( param->type < 5 && param->type > 0 ) {
        frame_type = frame_types[param->type];
    } else {
        return XVID_ERR_FAIL;
    }

    snprintf(BUFFER_CAT(log), BUFFER_REMAINING(log),
        "%c %d %d %d %d %d %d\n",
        frame_type, param->stats.quant, param->stats.kblks, param->stats.mblks,
        param->stats.ublks, param->stats.length, param->stats.hlength);

    return 0;
}

/**
 * Dispatch function for our custom plugin.
 * This handles the dispatch for the XviD plugin. It passes data
 * on to other functions for actual processing.
 *
 * @param ref Context pointer for the plugin
 * @param cmd The task given for us to complete
 * @param p1 First parameter (varies)
 * @param p2 Second parameter (varies)
 * @return Returns XVID_ERR_xxxx on failure, or 0 on success
 */
int xvid_ff_2pass(void *ref, int cmd, void *p1, void *p2) {
    switch( cmd ) {
        case XVID_PLG_INFO:
        case XVID_PLG_FRAME:
            return 0;

        case XVID_PLG_BEFORE:
            return xvid_ff_2pass_before(ref, p1);

        case XVID_PLG_CREATE:
            return xvid_ff_2pass_create(p1, p2);

        case XVID_PLG_AFTER:
            return xvid_ff_2pass_after(ref, p1);

        case XVID_PLG_DESTROY:
            return xvid_ff_2pass_destroy(ref, p1);

        default:
            return XVID_ERR_FAIL;
    }
}

/**
 * XviD codec definition for libavcodec.
 */
AVCodec libxvid_encoder = {
    "libxvid",
    CODEC_TYPE_VIDEO,
    CODEC_ID_XVID,
    sizeof(xvid_context_t),
    ff_xvid_encode_init,
    ff_xvid_encode_frame,
    ff_xvid_encode_close,
    .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, -1},
};