给出android av中在编码时使用kKeyIsSyncFrame 的完整代码

以下是使用android av中的kKeyIsSyncFrame在编码时的完整代码示例：

#include <media/stagefright/MediaCodec.h>
#include <media/stagefright/MediaCodecList.h>
#include <media/stagefright/MediaFormat.h>
#include <media/stagefright/Utils.h>

...

const char *mime = "video/avc";
int32_t width = 1280;
int32_t height = 720;
int32_t bitrate = 2000000;
int32_t frameRate = 30;
int32_t iFrameInterval = 1;

// Find a suitable encoder.
sp<MediaCodecList> list = MediaCodecList::getInstance();
sp<MediaCodecInfo> info = list->findEncoderByType(mime);
if (info == NULL) {
    // No suitable encoder found.
    return;
}

// Create a MediaFormat with the desired settings.
sp<MediaFormat> format = MediaFormat::Create();
format->setCString(kKeyMIMEType, mime);
format->setInt32(kKeyWidth, width);
format->setInt32(kKeyHeight, height);
format->setInt32(kKeyBitRate, bitrate);
format->setInt32(kKeyFrameRate, frameRate);
format->setInt32(kKeyIFramesInterval, iFrameInterval);

// Create a MediaCodec for encoding.
sp<MediaCodec> encoder = MediaCodec::CreateByInfo(
        env, info, false /* encoder */, NULL /* crypto */);

encoder->configure(format.get(), NULL /* surface */, NULL /* crypto */, MediaCodec::CONFIGURE_FLAG_ENCODE);

encoder->start();

// Start encoding.
bool sawInputEOS = false;
bool sawOutputEOS = false;
while (!sawOutputEOS) {
    if (!sawInputEOS) {
        ssize_t inputBufIndex = encoder->dequeueInputBuffer(kTimeoutUs);
        if (inputBufIndex >= 0) {
            sp<MediaCodecBuffer> inputBuf = encoder->getInputBuffer(inputBufIndex);

            // Read input data into the buffer.
            ...

            // Set kKeyIsSyncFrame metadata if this is a key frame.
            bool isKeyFrame = ...;
            if (isKeyFrame) {
                inputBuf->meta_data()->setInt32(kKeyIsSyncFrame, 1);
            } else {
                inputBuf->meta_data()->setInt32(kKeyIsSyncFrame, 0);
            }

            encoder->queueInputBuffer(
                    inputBufIndex,
                    0 /* offset */,
                    sampleSize,
                    presentationTimeUs,
                    flags);
        }
    }

    MediaCodecBuffer *outBuf = NULL;
    MediaCodec::BufferInfo outInfo;
    ssize_t outBufIndex = encoder->dequeueOutputBuffer(&outBuf, &outInfo, kTimeoutUs);
    if (outBufIndex >= 0) {
        if (outInfo.flags & MediaCodec::BUFFER_FLAG_END_OF_STREAM) {
            sawOutputEOS = true;
        }

        // Handle the output data.
        ...

        encoder->releaseOutputBuffer(outBufIndex, outInfo.size != 0);
    } else if (outBufIndex == MediaCodec::INFO_OUTPUT_BUFFERS_CHANGED) {
        // The output buffers have changed, we need to get a new set.
    } else if (outBufIndex == MediaCodec::INFO_OUTPUT_FORMAT_CHANGED) {
        // The output format has changed, we need to use the new format.
        sp<MetaData> newFormat = encoder->getOutputFormat();
        format = MediaFormat::FromMetaData(newFormat.get());
    }
}

// Stop and release the encoder.
encoder->stop();
encoder->release();

在上述代码中，当编码视频帧时，如果该帧是关键帧，则会将`kKeyIsSyncFrame`元数据设置为1，否则设置为0，以便在解码后进行使用。注意，具体判断是否为关键帧的逻辑需要根据具体的编码器实现进行调整。