Android平台GB28181设计开发的时候，有个功能必不可少的：实时快照，特别是用于执法记录仪等场景下，用于图像留底或分析等考量。
实时快照的实现并不难，目前实现有两种方式，一种是拿到数据（比如摄像头数据）后，直接上层编码，存取快照；另一种模式是，数据投递到JNI层，底层针对投递过来的编码前数据，做png编码，并保存到设定的目录下，今天我们主要探讨第二种实现模式。
我们在publisher实例初始化的时候，设置是否启用快照：
代码语言：javascript复制private void InitAndSetConfig() {
int audio_opt = 1;
int fps = 18;
int gop = fps * 2;
Log.i(TAG, "InitAndSetConfig video_width: " video_width_ " cur_video_height" video_height_ " imageRotationDegree:" cameraImageRotationDegree_);
publisherHandle = libPublisher.SmartPublisherOpen(context_, audio_opt, 3, video_width_, video_height_);
if (publisherHandle == 0) {
Log.e(TAG, "sdk open failed!");
return;
}
Log.i(TAG, "publisherHandle=" publisherHandle);
if(videoEncodeType == 1) {
int h264HWKbps = setHardwareEncoderKbps(true, video_width_, video_height_);
h264HWKbps = h264HWKbps*fps/25;
Log.i(TAG, "h264HWKbps: " h264HWKbps);
int isSupportH264HWEncoder = libPublisher
.SetSmartPublisherVideoHWEncoder(publisherHandle, h264HWKbps);
if (isSupportH264HWEncoder == 0) {
libPublisher.SetNativeMediaNDK(publisherHandle, 1);
Log.i(TAG, "Great, it supports h.264 hardware encoder!");
}
}
else if (videoEncodeType == 2) {
int hevcHWKbps = setHardwareEncoderKbps(false, video_width_, video_height_);
hevcHWKbps = hevcHWKbps*fps/25;
Log.i(TAG, "hevcHWKbps: " hevcHWKbps);
int isSupportHevcHWEncoder = libPublisher
.SetSmartPublisherVideoHevcHWEncoder(publisherHandle, hevcHWKbps);
if (isSupportHevcHWEncoder == 0) {
libPublisher.SetNativeMediaNDK(publisherHandle, 1);
Log.i(TAG, "Great, it supports hevc hardware encoder!");
}
}
boolean is_sw_vbr_mode = true;
if(is_sw_vbr_mode) //H.264 software encoder
{
int is_enable_vbr = 1;
int video_quality = CalVideoQuality(video_width_, video_height_, true);
int vbr_max_bitrate = CalVbrMaxKBitRate(video_width_, video_height_);
libPublisher.SmartPublisherSetSwVBRMode(publisherHandle, is_enable_vbr, video_quality, vbr_max_bitrate);
}
if (is_pcma_) {
libPublisher.SmartPublisherSetAudioCodecType(publisherHandle, 3);
} else {
libPublisher.SmartPublisherSetAudioCodecType(publisherHandle, 1);
}
libPublisher.SetSmartPublisherEventCallbackV2(publisherHandle, new EventHandePublisherV2());
libPublisher.SmartPublisherSetSWVideoEncoderProfile(publisherHandle, 3);
libPublisher.SmartPublisherSetSWVideoEncoderSpeed(publisherHandle, 2);
libPublisher.SmartPublisherSetGopInterval(publisherHandle, gop);
libPublisher.SmartPublisherSetFPS(publisherHandle, fps);
// libPublisher.SmartPublisherSetSWVideoBitRate(publisherHandle, 600, 1200);
boolean is_noise_suppression = true;
libPublisher.SmartPublisherSetNoiseSuppression(publisherHandle, is_noise_suppression ? 1 : 0);
boolean is_agc = false;
libPublisher.SmartPublisherSetAGC(publisherHandle, is_agc ? 1 : 0);
int echo_cancel_delay = 0;
libPublisher.SmartPublisherSetEchoCancellation(publisherHandle, 1, echo_cancel_delay);
libPublisher.SmartPublisherSaveImageFlag(publisherHandle, 1);
}记得留意最后一句：libPublisher.SmartPublisherSaveImageFlag(publisherHandle, 1);
相关接口说明如下：
代码语言：javascript复制 /**
* Set if needs to save image during publishing stream(设置是否启用快照)
*
* @param is_save_image: if with 1, it will save current image via the interface of SmartPlayerSaveImage(), if with 0: does not it
*
* @return {0} if successful
*/
public native int SmartPublisherSaveImageFlag(long handle, int is_save_image);设置后，页面有需要实时快照的数据时，点击“实时快照”按钮即可，需要注意的是，实时快照需要存储路径和保存下来的快照文件名称。具体实现如下：
代码语言：javascript复制class ButtonCaptureImageListener implements View.OnClickListener {
@SuppressLint("SimpleDateFormat")
public void onClick(View v) {
if(isPushingRtmp || isRecording || isRTSPPublisherRunning || isGB28181StreamRunning)
{
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
String imageFileName = "dn_" timeStamp; //创建以时间命名的文件名称
String imagePath = imageSavePath "/" imageFileName ".png";
Log.i(TAG, "imagePath:" imagePath);
libPublisher.SmartPublisherSaveCurImage(publisherHandle, imagePath);
}
else
{
Log.e(TAG, "快照失败，请确保在推送、录像、GB28181推送或内置RTSP服务发布状态..");
}
}
}快照截取成功后，publisher实例会回调以下事件：
代码语言：javascript复制case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_CAPTURE_IMAGE:
publisher_event = "快照: " param1 " 路径：" param3;
if (param1 == 0) {
publisher_event = publisher_event "截取快照成功..";
} else {
publisher_event = publisher_event "截取快照失败..";
}
break;由于实时快照，功能复杂度不高，而且也可以在上层实现，很容易被忽略，如果做的精细的话，还是需要开发者花费一定的心思。
