UsageExampleForEncoder

This page is about the example of encoder usage

• Encoder Usage Example-1
• Encoder Usage Example-2

Encoder Usage Example-1

Encoder usage example 1

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• An example for using encoder with basic parameter

Step1: setup encoder

int rv = WelsCreateSVCEncoder (&encoder_);
ASSERT_EQ (0, rv);
ASSERT_TRUE (encoder_ != NULL);

Step2: initialize with basic parameter

(note: definition of SEncParamBase can be found: https://github.com/cisco/openh264/blob/master/codec/api/svc/codec_app_def.h#L517 )

SEncParamBase param;
memset (&param, 0, sizeof (SEncParamBase));
param.iUsageType = usageType;
param.fMaxFrameRate = frameRate;
param.iPicWidth = width;
param.iPicHeight = height;
param.iTargetBitrate = 5000000;
encoder_->Initialize (&param);

Step3:set option, set option during encoding process

//changing logging granularity
encoder_->SetOption (ENCODER_OPTION_TRACE_LEVEL, &g_LevelSetting);

int videoFormat = videoFormatI420;
encoder_->SetOption (ENCODER_OPTION_DATAFORMAT, &videoFormat);

//changing encoding param
SEncParamBase param;
//fill in instant param content
encoder_->SetOption (ENCODER_OPTION_SVC_ENCODE_PARAM_BASE, &param);

Step4: encode and store output bistream

int frameSize = width * height * 3 / 2;
BufferedData buf;
buf.SetLength (frameSize);
ASSERT_TRUE (buf.Length() == (size_t)frameSize);
SFrameBSInfo info;
memset (&info, 0, sizeof (SFrameBSInfo));
SSourcePicture pic;
memset (&pic, 0, sizeof (SsourcePicture));
pic.iPicWidth = width;
pic.iPicHeight = height;
pic.iColorFormat = videoFormatI420;
pic.iStride[0] = pic.iPicWidth;
pic.iStride[1] = pic.iStride[2] = pic.iPicWidth >> 1;
pic.pData[0] = buf.data();
pic.pData[1] = pic.pData[0] + width * height;
pic.pData[2] = pic.pData[1] + (width * height >> 2);
for(int num = 0;num<total_num;num++) {
   //prepare input data
   rv = encoder_->EncodeFrame (&pic, &info);
   ASSERT_TRUE (rv == cmResultSuccess);
   if (info.eFrameType != videoFrameTypeSkip && cbk != NULL) {
    //output bitstream
   }
}

Step5:teardown encoder

if (encoder_) {
    encoder_->Uninitialize();
    WelsDestroySVCEncoder (encoder_);
}

Encoder Usage Example-2

Encoder usage example 2

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• An example for using the encoder with extension parameter.
• The same operation on Step 1,3,4,5 with Example-1

Step 2:initialize with SEncParamExt

Note: for more details on available sliceMode and their usage, refer to https://github.com/cisco/openh264/blob/master/codec/api/svc/codec_app_def.h#L335

SEncParamExt param;
encoder->GetDefaultParams (&param);
param.iUsageType = usageType;
param.fMaxFrameRate = frameRate;
param.iPicWidth = width;
param.iPicHeight = height;
param.iTargetBitrate = 5000000;
param.bEnableDenoise = denoise;
param.iSpatialLayerNum = layers;
//SM_SIZELIMITED_SLICE with multi-thread is still under testing
if (sliceMode != SM_SINGLE_SLICE && sliceMode != SM_SIZELIMITED_SLICE)
    param.iMultipleThreadIdc = 2;

for (int i = 0; i < param.iSpatialLayerNum; i++) {
    param.sSpatialLayers[i].iVideoWidth = width >> (param.iSpatialLayerNum - 1 - i);
    param.sSpatialLayers[i].iVideoHeight = height >> (param.iSpatialLayerNum - 1 - i);
    param.sSpatialLayers[i].fFrameRate = frameRate;
    param.sSpatialLayers[i].iSpatialBitrate = param.iTargetBitrate;

    param.sSpatialLayers[i].sSliceCfg.uiSliceMode = sliceMode;
    if (sliceMode == SM_SIZELIMITED_SLICE) {
        param.sSpatialLayers[i].sSliceCfg.sSliceArgument.uiSliceSizeConstraint = 600;
        param.uiMaxNalSize = 1500;
    }
}
param.iTargetBitrate *= param.iSpatialLayerNum;
encoder_->InitializeExt (&param);
int videoFormat = videoFormatI420;
encoder_->SetOption (ENCODER_OPTION_DATAFORMAT, &videoFormat);