《鸿蒙开发-答案之书》获取视频第一帧和视频时间

/**
     * 获取视频信息
     *```
     *let result = await MySightUtil.getSightInfo(this.sightUri);
     *let base64 : string = result[0];
     *let duration : number = result[1]
     *```
     * @param uri 视频地址
     * @returns 第一个数据是缩略图 base64 字符串，第二个是视频时长（单位秒）
     */
    public static async getSightInfo(uri: string): Promise<[string, number]> {
        let file = fs.openSync(uri, fs.OpenMode.READ_ONLY);
        let fdSrc: media.AVFileDescriptor = {
            fd: file.fd
        };

        // 视频第一帧
        let base64 = '';
        try {
            // 获取第一帧
            let avImageGenerator: media.AVImageGenerator = await media.createAVImageGenerator();
            // 设置fdSrc

            avImageGenerator.fdSrc = fdSrc;
            // 初始化入参
            let timeUs = 0;
            let queryOption = media.AVImageQueryOptions.AV_IMAGE_QUERY_NEXT_SYNC;
            let param: media.PixelMapParams = {};
            // 获取缩略图（promise模式）
            let pixelMap = await avImageGenerator.fetchFrameByTime(timeUs, queryOption, param);
            // 释放资源（promise模式）
            await avImageGenerator.release();
            const MAX_SIZE = 240;
            const MIN_SIZE = 100;
            await calculateThumbnailScaling(pixelMap, MAX_SIZE, MIN_SIZE);

            const imagePackerApi: image.ImagePacker = image.createImagePacker();
            let packOpts: image.PackingOption = { format: 'image/jpeg', quality: 80 };
            let data: ArrayBuffer = await imagePackerApi.packing(pixelMap, packOpts);
            let buf: buffer.Buffer = buffer.from(data);
            base64 = buf.toString('base64', 0, buf.length);
        } catch (error) {
            let err = error as BusinessError;
            hilog.error(0x0000, '', `error code: ${err.code}, error message: ${err.message}`);
        }

        // 视频时长
        let duration: number = 0;
        try {
            // 获取视频时长
            let aVMetadataExtractor: media.AVMetadataExtractor = await media.createAVMetadataExtractor();
            aVMetadataExtractor.fdSrc = fdSrc;
            let metadata = await aVMetadataExtractor.fetchMetadata();
            aVMetadataExtractor.release();
            // 毫秒
            duration = new Number(metadata.duration).valueOf();

            hilog.error(0x0000, 'IM-APP', `metadata: %{public}s`, JSON.stringify(metadata));
        } catch (error) {
            let err = error as BusinessError;
            hilog.error(0x0000, '', `error code: ${err.code}, error message: ${err.message}`);
        }

        return [base64, duration / 1000];
    }