rpi-omx-jpeg-encode

Hardware JPEG Encoding on Raspberry Pi using OpenMAX IL.

Description

This repository contains source code to utilize the hardware JPEG encoder on the RPi GPU to do JPEG encoding.

Building

make clean && make all

Usage

./jpeg-bench <frame_count> > <jpeg_data_output>
Recommended <jpeg_data_output> to /dev/null
Example: ./jpeg-bench 20 > /dev/null
If you want to output single JPEG image with OMX Encoder, modify the soruce code of jpeg_bench.cpp, set "ENABLE_WRITE_IN_B4" to 1 and others to 0, compile and run with ./jpeg_bench 1 > ./omx_image.jpg

Files

Makefile:

Makefile for the project

jpeg_bench.cpp:

Contains 4 benchmarks which compare jpeg encoding speed with openCV.

The speedup is over 1x tested on RPi 2.

Benchmark 1: openCV JPEG decode and openCV JPEG encode

Benchmark 2: openCV JPEG decode and openCV JPEG encode with 1/2 resize

Benchmark 3: openCV JPEG decode and openCV JPEG encode with 1/2 pryDown

Benchmark 4: openCV JPEG decode and RPi OMX Hardware JPEG encode

jpeg_bench.cpp relies on jpeg_bench_image.h, which provide smaple JPEG data for decoding.

The image is taken from wikimedia:

https://commons.wikimedia.org/wiki/File:Burosch_Blue-Only_Test_pattern.jpg

The supplied image is 1280*720 in size, feel free to use your own image in any size, remember to modify the following values when you do so:

jpeg_bench.cpp marcos:   
IMAGE_WIDTH		(JPEG image width)
IMAGE_HEIHGT	(JPEG image height)
IMAGE_CHANNELS	(JPEG image channels, usually 3)

jpeg_bench_image.h marcos:
JPEG_DATA_SIZE	(JPEG image size)

jpeg_bench_image.h variables:
jpegData		(JPEG image data)

Test results

• Raspberry Pi 2, 200 frames

  [1] openCV JPEG decode and encode

  Result CPU Clocks: 24359705 (24s)

  [2] openCV JPEG decode and encode with openCV resize 1/2 *

  Result CPU Clocks: 16562283 (16s)

  [3] openCV JPEG decode and encode with openCV pryDown 1/2 *

  Result CPU Clocks: 19074908 (19s)

  [4] openCV JPEG decode and OMX encode

  Result CPU Clocks: 10463216 (10s)

Additional Notes

You can extract the omx code in jpeg_bench.cpp and copy into your project to use the OMX Hardware JPEG Encoder. It is quite nice to use that to replace openCV imencode for JPEG as the speed up is quite noticable.

Despite the openCV Mat is using BGR888 structure, you need to configure the OMX Encoder to RGB888 to have correct image output. Please refer to this for more information.

Note to RPi1 user: The Makefile used NEON and VFPv4 optimizations which are not supported in RPi1, please remove those from the cflags.

Feature in the future

• Add options to modify the QFactor of the JPEG encoder

Known Bugs

• None yet

Tested Resolution

• 640x480
• 1280x720
• 1920x1080

References

• Supplied image: https://commons.wikimedia.org/wiki/File:Burosch_Blue-Only_Test_pattern.jpg
• OMX Encoder inspiration: OpenMAX IL demos for Raspberry Pi