Segmentation Fault Triggered by NvJPEGEncoder::encodeFromBuffer on Nvidia Jetson Orin Nano

Issue Overview

Users of the Nvidia Jetson Orin Nano development board, specifically those running Jetpack version 5.1.3, are encountering segmentation faults (SIGSEGV) when using the NvJPEGEncoder::encodeFromBuffer function. This issue arises during the encoding of images with certain resolutions, particularly when multiple threads create instances of nvjpegencoder objects.

Symptoms

• Error Message: The error reported is a segmentation fault triggered during the execution of the __memcpy_generic() function, indicating an issue with memory access.
• Stack Trace: The stack trace shows that the fault occurs within the jpeg_write_raw_data() function from the libnvjpeg.so library.
• Threading Issues: The problem persists even when mutexes are employed to prevent concurrent access to the encoder objects.

Context

• Environment: The issue occurs in a multi-threaded environment where multiple instances of nvjpegencoder are being created.
• Image Resolutions: Specific resolutions have been identified that consistently trigger the fault, particularly those between 1000×850 and 1200×950 pixels.
• Frequency: The segmentation fault does not occur consistently across all resolutions; smaller widths seem to avoid triggering the error.

Impact

The segmentation fault significantly disrupts user experience, as it leads to application crashes and hinders functionality related to image encoding. This can affect any application relying on JPEG compression, particularly in real-time processing scenarios.

Possible Causes

• Input Image Size: Certain image resolutions may exceed buffer limits or cause memory mismanagement.

• Memory Allocation Issues: Insufficient allocation for output buffers can lead to attempts to write beyond allocated memory.

• Threading Conflicts: Despite using mutexes, race conditions may still occur if shared resources are not properly managed.

• Library Bugs: Potential bugs in the Nvidia JPEG library (libnvjpeg.so) or its interaction with specific hardware configurations could lead to instability.

• Driver Issues: Incompatibilities or bugs in the underlying drivers for Jetpack 5.1.3 might contribute to these segmentation faults.

Troubleshooting Steps, Solutions & Fixes

Step-by-Step Diagnosis

1. Reproduce the Issue:

   • Compile and run the default JPEG encoding sample located at /usr/src/jetson_multimedia_api/samples/05_jpeg_encode.
   • Use various image resolutions to identify which ones trigger the segmentation fault.

2. Check Memory Allocation:

   • Ensure that the output image buffer is allocated correctly:

     int mallocSize = imgWidth * imgHeight * 3 / 2;
     pOutputImageBuffer = (unsigned char*)malloc(mallocSize);
     outputImageBufferSize = mallocSize;
     

3. Test Different Encoding Methods:

   • Instead of using encodeFromBuffer(), try using encodeFromFd() as a workaround:

     jpegencoder->encodeFromFd(fd, JCS_YCbCr, outputImageBuffer, outputImageBufferSize);
     

4. Validate Input Parameters:

   • Confirm that all parameters passed to encodeFromBuffer() are valid and within expected ranges.

5. Use Debugging Tools:

   • Utilize GDB to trace errors further:

     gdb --arg ./jpeg_encode input_image.bin width height output_image.jpg --encode-buffer
     

Recommended Solutions

• Adjust Image Resolutions: If possible, limit the width of images being processed to avoid problematic sizes identified in user reports.

• Implement Error Handling: Add robust error handling around memory allocations and encoding calls to gracefully manage failures.

• Update Software: Ensure that all software components, including Jetpack and associated libraries, are up-to-date with the latest patches that may address known issues.

Best Practices for Future Prevention

• Regularly test applications against different versions of Jetpack and libraries to catch compatibility issues early.

• Use static analysis tools to identify potential threading issues and memory mismanagement in code.

Unresolved Aspects

While several users have successfully implemented workarounds such as switching from encodeFromBuffer() to encodeFromFd(), further investigation into specific resolutions causing faults is needed. Continued collaboration with Nvidia support may yield additional insights and fixes for this issue.