When using the NvJPEGEncoder interface of jetson_multimedia_api, connecting the DP port to a monitor will affect the encoding performance

[deeptalkcamera]

HI:

My device is: Jetson AGX Orin Developer Kit
The version of jetpack is:
Package: nvidia-jetpack
Version: 5.1.2-b104

I tested jetson_multimedia_api/samples/05_jpeg_encode and added time printing in jpeg_encode_main.cpp. I found that when the DP monitor is connected, the time of end_time - start_time is about 11ms, but when the DP monitor is not connected, this time increases to more than 30ms. Can you explain this phenomenon?

        clock_gettime(CLOCK_MONOTONIC, &real_tp);
        start_time = real_tp.tv_sec * 1000000000ULL + real_tp.tv_nsec;

        ret = ctx.jpegenc->encodeFromFd(dst_dma_fd, JCS_YCbCr, &out_buf,
              out_buf_size, ctx.quality);

	clock_gettime(CLOCK_MONOTONIC, &real_tp);
        end_time = real_tp.tv_sec  * 1000000000ULL + real_tp.tv_nsec;
        cout << "nielei_debug, frame:" << file_num  <<" Time taken for encoding: " << (end_time - start_time) << " ns" << endl;

Can it be considered that NvJPEGEncoder does not use the GPU?

In addition, my image size is 1600*1300. Is the time of 11ms in line with expectations? How to improve encoding performance

[deeptalkcamera]

In addition, when the DP monitor is connected, run jtop of NvJPEGEncoder

[DaneLLL]

Hi,
Are you able to try Jetpack 6.2 r36.4.3? Certain issues are discovered and fixed in later release. Would suggest upgrade and try.

[deeptalkcamera]

Hi, DaneLLL:

Sorry, we need to develop based on the current Jetpack and cannot upgrade.
I have a few questions:
1, Can it be considered that NvJPEGEncoder does not use the GPU? Is it a bug that NvJPEGEncoder becomes slow when not connecting a DP monitor?
2, My image size is 1600*1300. Is the time of 11ms in line with expectations? The running frequency of NvJPG is 729MHz. Can it be improved? If it cannot be increased，How to improve NvJPG encoding performance?

Thanks!

[deeptalkcamera]

Can anyone help answer this question?

[DaneLLL]

Hi,
There is individual NVJPG engine to do JPEG encoding/decoding. It is not executed on GPU. The maximum clock of each engine is listed in

Jetson Orin Nano Series, Jetson Orin NX Series and Jetson AGX Orin Series — NVIDIA Jetson Linux Developer Guide

On Orin 32GB, maximum clock of NVJPG is 729.6MHz.

If you would like to develop the use-case without display, would suggest run in headless mode. You may refer to developer guide to generate headless rootfs:

Root File System — NVIDIA Jetson Linux Developer Guide

[deeptalkcamera]

Thank you very much for your reply.

Can you further explain the impact of connecting a monitor and not connecting a monitor on the computing resources (CPU, GPU, etc.) in the system?

From the phenomenon, it seems that connecting a monitor helps improve the performance of NvJPEGEncoder::encodeFromFd(). This is a very interesting phenomenon. I would like to know the reason.

[DaneLLL]

Hi,
This is not a valid setup. We would expect display output device is present when it’s enabled in device tree. Certain use-cases may not work properly in the setup.