How to save YUV420 buffer with Pitch layout into YUV file?

Autonomous Machines Jetson & Embedded Systems Jetson TX2
1

Hi, I’m using TX2 NX with JP 4.6.3.

I’m having a NvBuffer created by NvBufferCreateEx() with params

        NvBufferCreateParams params = {
            .width = 1920,
            .height = 1080,
            .payloadType = NvBufferPayload_SurfArray,
            .memsize = 1,
            .layout = NvBufferLayout_Pitch,
            .colorFormat = NvBufferColorFormat_YUV420,
            .nvbuf_tag = NvBufferTag_CAMERA
        };

The image data was copied from another buffer to this by transform function.
My question is, how to save this buffer into YUV420 binary file correctly?

This is what I did:

    NvBufferParams buf_params;

    if (NvBufferGetParams (fd, &buf_params) != 0) {
        return -1;
    }

        void *pdata = NULL;
        NvBufferMemMap(fd, 0, NvBufferMem_Read, &pdata);
        NvBufferMemSyncForCpu(fd, 0, &pdata);
        // printf("saving image %dx%d into YUV file '%s', pitch %d\n", width, height, path, pitch);
        printf("planes %d, %ux%u pitch %u offset %u psize %u layout %u, %ux%u pitch %u offset %u psize %u layout %u, , %ux%u pitch %u offset %u psize %u layout %u\n", buf_params.num_planes,
            buf_params.width[0], buf_params.height[0], buf_params.pitch[0], buf_params.offset[0], buf_params.psize[0], buf_params.layout[0],
            buf_params.width[1], buf_params.height[1], buf_params.pitch[1], buf_params.offset[1], buf_params.psize[1], buf_params.layout[1],
            buf_params.width[2], buf_params.height[2], buf_params.pitch[2], buf_params.offset[2], buf_params.psize[2], buf_params.layout[2]);

        FILE *f = fopen(path, "w");
        // Write Y
        void *data = pdata + buf_params.offset[0];
        uint32_t writen = 0;
        for (int i = 0; i < buf_params.height[0]; ++i) {
            writen += fwrite(data , 1, buf_params.width[0], f);
            data += buf_params.pitch[0];
        }
        printf("  wrote %ubytes Y\n", writen);
        // write u
        data = pdata + buf_params.offset[1];
        writen = 0;
        for (int i = 0; i < buf_params.height[1]; ++i) {
            writen += fwrite(data , 1, buf_params.width[1], f);
            data += buf_params.pitch[1];
        }
        printf("  wrote %ubytes U\n", writen);
        // write V
        data = pdata + buf_params.offset[2];
        writen = 0;
        for (int i = 0; i < buf_params.height[2]; ++i) {
            writen += fwrite(data , 1, buf_params.width[2], f);
            data += buf_params.pitch[2];
        }
        printf("  wrote %ubytes V\n", writen);

        fclose(f);

        NvBufferMemUnMap(fd, 0, &pdata);

This is what it printed when saving file:

planes 3, 1920x1080 pitch 2048 offset 0 psize 2228224 layout 0, 960x540 pitch 1024 offset 2228224 psize 655360 layout 0, , 960x540 pitch 1024 offset 2883584 psize 655360 layout 0                                                            
  wrote 2073600bytes Y                                                                                                 
  wrote 518400bytes U                                                                                                  
  wrote 518400bytes V

But the saved file looks really weird, looks like not even a line is correctly written.
Can you please point me that I did something wrong or is there any better way or example code for this? Thank you.

3

hello Hnil.DN,

had you tried Applications Using V4L2 IOCTL Directly by using V4L2 IOCTL to dump the content for checking?
you may see-also MMAPI sample app, 07_video_convert for sample codes.

4

Thank you for pointing out the sample app. It works with this sample.

6

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