17.1. HPM_JPEG

17.1.1. Overview

The HPM_JPEG sample performs encoding and decoding through the HPM_JPEG component. After decoding, the file is displayed on the screen, and the decoded image is re-encoded and stored.

17.1.2. Hardware Setup

  • USB Disk is connected to the development board’s USB0 port (Attention: The Cluster Size of the USB disk can’t exceed 32KB, it is recommended that the format parameter is FAT32/32KB), or the SD card is inserted into the development board’s sd card slot.

    UDisk_Format

  • LCD screen is connected to the development board.

17.1.3. Project Configuration

  • File CMakeLists.txt:

    • set (JPEG_USE_SDCARD 1) : Read the test.jpg file from the SD card;

    • set (JPEG_USE_UDISK 1) : Read the test.jpg file from the USB drive. These two options are mutually exclusive.

17.1.4. Running Behavior

  • Modify the CMakeLists.txt file as needed to configure the target storage/decoding method.

  • Copy the test.jpg file to the root directory of the target storage.

  • Connect the LCD screen and storage medium to the development board.

  • Power on the development board.

  • Download the compiled ELF file to the development board.

  • If everything is set up correctly, the test.jpg file from the storage medium will be displayed on the screen, aligned with the top-left corner. The decoded image will not be scaled; if the image size exceeds the screen size, only the top-left portion will be shown. If the decoded image is smaller than the screen, the remaining areas will be filled with black pixels to highlight the image boundary.

  • After execution, the decoded image will be re-encoded into a test_yuv422.jpg with a 90% compression ratio and a test_yuv420.jpg with a 40% compression ratio, and saved to the root directory of the target storage.

  • If the codec fails because the encoded image is too large, increase the HEAP_SIZE

SD card has been mounted successfully
Read picture data by SD card
djob0 callback hw_status: 0x8000001c
decode: width: 640
decode: height: 480
decode: stride: 1280
ejob0 callback hw_status: 0x1c
ejob1 callback hw_status: 0x1c
save 36682 bytes to /test_yuv422.jpg finished
save 10736 bytes to /test_yuv420.jpg finished
hpm_jpeg sample end!