问题描述
嗯,我的目标很简单——尝试从带有打包/交错 BGR 数据(也可以是 RGB)的缓冲区创建一个 JPEG 编码的图像。
NVidia 文档包含 example,正确的图像输入本质上描述为 here。
所以我尝试了以下方法:
#include <nvjpeg.h>
// very simple
typedef struct {
int width;
int height;
unsigned char *buffer;
unsigned long data_size;
} my_bitmap_type;
std::vector<unsigned char> BitmapToJpegCUDA(const my_bitmap_type *image)
{
nvjpegHandle_t nv_handle;
nvjpegEncoderState_t nv_enc_state;
nvjpegEncoderParams_t nv_enc_params;
cudaStream_t stream = NULL;
nvjpegStatus_t er;
nvjpegCreateSimple(&nv_handle);
nvjpegEncoderStateCreate(nv_handle,&nv_enc_state,stream);
nvjpegEncoderParamsCreate(nv_handle,&nv_enc_params,stream);
nvjpegImage_t nv_image;
nv_image.channel[0] = image->buffer;
nv_image.pitch[0] = 3 * image->width;
// nope,that's for planar images!
// nv_image.channel[0] = image->buffer;
// nv_image.channel[1] = image->buffer + image->width * image->height;
// nv_image.channel[2] = image->buffer + 2 * image->width * image->height;
// nv_image.pitch[0] = image->width;
// nv_image.pitch[1] = image->width;
// nv_image.pitch[2] = image->width;
er = nvjpegEncodeImage(nv_handle,nv_enc_state,nv_enc_params,&nv_image,NVJPEG_INPUT_BGRI,image->width,image->height,stream);
LOG(ERROR) << "enc " << er;
size_t length = 0;
nvjpegEncodeRetrieveBitstream(nv_handle,NULL,&length,stream);
cudaStreamSynchronize(stream);
std::vector<unsigned char> jpeg(length);
nvjpegEncodeRetrieveBitstream(nv_handle,jpeg.data(),0);
nvjpegEncoderParamsDestroy(nv_enc_params);
nvjpegEncoderStateDestroy(nv_enc_state);
nvjpegDestroy(nv_handle);
return jpeg;
}
记录器说 nvjpegEncodeImage
只返回 NVJPEG_STATUS_INVALID_ParaMETER
,这意味着没有任何作用。如果您怀疑 my_bitmap_type
填写错误,这里是类似的 turbojpeg 编码:
#include <turbojpeg.h>
std::vector<unsigned char> BitmapToJpegBuffer(const my_bitmap_type *image)
{
std::vector<unsigned char> out_data(3 * image->width * image->height);
cudaError_t err = cudamemcpy(out_data.data(),image->buffer,image->data_size,cudamemcpyDevicetoHost);
if (cudaSuccess != err) {
LOG(ERROR) << "Failed to copy CUDA memory: " << err;
}
tjhandle jpeg = tjInitCompress();
unsigned char *encoded_buf = nullptr;
long unsigned int encoded_sz = 0;
int tjres = tjCompress2(jpeg,out_data.data(),image->width * 3,TJPF_BGR,&encoded_buf,&encoded_sz,TJSAMP_444,95,TJFLAG_FASTDCT);
if (tjres != 0) {
LOG(ERROR) << "jpeg compession Failed!";
return {};
}
std::vector<unsigned char> result(encoded_buf,encoded_buf + encoded_sz);
tjFree(encoded_buf);
tjDestroy(jpeg);
return result;
}
... aa它工作得很好。
我非常想弄清楚代码中缺少什么。非常感谢任何帮助或建议。
UPD: 使用 CentOS 7 / libnvjpeg-11-1.x86_64 (CUDA 11.1) / gcc 4.8.5
解决方法
好吧,这有点奇怪,但经过一段时间的反复试验,发现 NVidia 文档缺少基本细节:
nvjpegCreateSimple(&nv_handle);
nvjpegEncoderStateCreate(nv_handle,&nv_enc_state,stream);
nvjpegEncoderParamsCreate(nv_handle,&nv_enc_params,stream);
// This has to be done,default params are not sufficient
nvjpegEncoderParamsSetSamplingFactors(nv_enc_params,NVJPEG_CSS_444,stream);
尽管文档明确指出 JPEG 压缩的默认子采样为 4:4:4,但编码不适用于默认编码器参数,因此必须明确设置子采样。
所以,那一行代码解决了所有问题。