AVAssetWriter编解码器类型hevc

Question

我正在尝试使用AVAssetWriter将H264视频转码为HEVC，但在iPhone 6s上失败。据推测，iPhone 6s支持HEVC进行转码，而不是实时视频编码。同样的代码也适用于iPhone 7及更高版本。如果iPhone 6s不支持HEVC编解码器，我们如何在运行时以编程方式确定支持的编解码器？

let bitrate = trackBitrate / 5 
let trackDimensions = trackSize
let compressionSettings: [String: Any] = [
    AVVideoAverageBitRateKey: bitrate,
    AVVideoMaxKeyFrameIntervalKey: 30,
    AVVideoProfileLevelKey: kVTProfileLevel_HEVC_Main_AutoLevel
]
var videoSettings: [String : Any] = [
    AVVideoWidthKey: trackDimensions.width,
    AVVideoHeightKey: trackDimensions.height,
    AVVideoCompressionPropertiesKey: compressionSettings
]

videoSettings[AVVideoCodecKey] =  AVVideoCodecType.hevc

Answer 1

我最终是这样做的

if #available(iOS 11.0, *),  AVCaptureVideoDataOutput().availableVideoCodecTypes.contains(.hevc) {
    // use .hevc settings here
} else {
    // use .h264 settings here
}

如果您的应用程序以< iOS 11为目标，则需要进行#available检查以使编译器满意

Answer 2

您可以通过以下代码获取iPhone模型：

+ (NSString *) deviceModel {
    struct utsname systemInfo;
    uname(&systemInfo);

    return [NSString stringWithCString: systemInfo.machine encoding: NSUTF8StringEncoding];
}

并确定iPhone 6S是否禁用H265编码，上面的iPhone7是否启用H265编码。