Rockchip Android libhwjpeg: JPEG encoding and decoding

Applicability and source

This platform reference preserves RK-SM-YF-E10 V1.0.0, the Chinese Rockchip Android Libhwjpeg Interface document. The source lists Linux 4.19 and 5.10 and says “all chips”; that wording is a source claim, not confirmation for every ArmSoM board. Confirm that your Android BSP includes the matching MPP/libhwjpeg implementation and headers. No ArmSoM hardware or code execution was tested for this article. No English PDF or technical figures were supplied.

1 Overview

The libhwjpeg library supports hardware JPEG encoding and decoding on Rockchip platforms by wrapping the JPEG logic in MPP (Media Process Platform). MpiJpegEncoder wraps hardware encoding; MpiJpegDecoder wraps hardware decoding of images or MJPEG streams. The project directories are:

• inc: libhwjpeg headers.
• src: implementation.
• test: test examples.

The project uses bp build files and can be built directly in the Android SDK environment.

2 MpiJpegDecoder

MpiJpegDecoder wraps the platform JPEG hardware decoder and accepts JPG images or MJPEG streams, with synchronous and asynchronous decoding.

decodePacket(char* data, size_t size, OutputFrame_t *frameOut);
decodeFile(const char *inputFile, const char *outputFile);

decodePacket and decodeFile are synchronous: they block until decoded output is available. OutputFrame_t wraps the output frame, including width, height, physical address and virtual address.

sendpacket(char* data, size_t size);
getoutframe(OutputFrame_t *frameOut);

sendpacket and getoutframe cooperate for asynchronous decoding. Start two application threads: one sends input through sendpacket, while the other retrieves output asynchronously through getoutframe.

Decoder notes

1. The default output is RAW NV12.
2. Hardware-decoded YUV output is aligned by default. Before display, crop the actual image using the buffer’s virtual width and height; otherwise green borders may appear. libhwjpeg provides internal cropping through the property below.
3. OutFrame buffers wrap output dmaBuffers and are reused internally. After displaying a decoded frame, release it with deinitOutputFrame.
4. Output normally uses an internally allocated rotating buffer pool. An external dmaBuffer fd is also accepted through OutputFrame_t->outputPhyAddr in the decodePacket arguments.

setprop hwjpeg_dec_debug 0x10

Decoder example

MpiJpegDecoder decoder;
MpiJpegDecoder::OutputFrame_t frameOut;

memset(&frameOut, 0, sizeof(frameOut));

err = decoder.prepareDecoder();
if (!err) {
    ALOGE("failed to prepare JPEG decoder");
    goto cleanUp;
}

err = decoder.decodePacket(data, size, &frameOut);
if (!err) {
    ALOGE("failed to decode packet");
    goto cleanUp;
}

/* TODO - Get diaplay for the frameOut.
 * - frame address: frameOut.MemVirAddr
 * - frame size: frameOut.OutputSize */

/* output buffer count within limits, so release frame buffer if one
frame has been display successfully. */
decoder.deinitOutputFrame(&frameOut);

decoder.flushBuffer();

3 MpiJpegEncoder

MpiJpegEncoder wraps JPEG hardware encoding. Its principal interfaces follow.

encodeFrame(char *data, OutputPacket_t *packetOut);
encodeFile(const char *inputFile, const char *outputFile);

encodeFrame and encodeFile encode synchronously and block. OutputPacket_t wraps the encoded output and its memory-address information.

encode(EncInInfo *inInfo, EncOutInfo *outInfo);

The encode interface is designed for cameraHal. It accepts input and output dmaBuffer fds supplied by the caller. Its output JPEG contains an encoded thumbnail, an APP1 EXIF header and related information.

OutputPacket_t buffers are reused internally. After encoding is complete, release the output with deinitOutputPacket.

Encoder example

MpiJpegEncoder encoder;
MpiJpegEncoder::OutputPacket_t pktOut;

memset(&pktOut, 0, sizeof(pktOut));

err = encoder.prepareEncoder();
if (!err) {
    ALOGE("failed to prepare JPEG encoder");
    goto cleanUp;
}

err = encoder.updateEncodeCfg(
    720 /*width*/, 1080 /*height*/, MpiJpegEncoder::INPUT_FMT_YUV420SP);
if (!err) {
    ALOGE("failed to update encode config");
    goto cleanUp;
}

err = encoder.encodeFrame(data, &pktOut);
if (!err) {
    ALOGE("failed to encode packet");
    goto cleanUp;
}

/* TODO - Get diaplay for the PacketOut.
 * - Pakcet address: pktOut.data
 * - Pakcet size: pktOut.size */

/* output buffer count within limits, so release frame buffer if one
frame has been display successful. */
encoder.deinitOutputPacket(&pktOut);

encoder.flushBuffer();

Source issues to verify

Both examples preserve the source’s if (!err) tests and goto cleanUp, even though the return-value convention and cleanup label are not defined in the excerpt. They are source excerpts, not complete standalone programs. The diaplay and Pakcet comment typos are retained. Verify the use of OutputFrame_t->outputPhyAddr to carry an fd against the actual SDK header; do not infer field semantics solely from its name.

Official reference: Rockchip MPP, ArmSoM documentation.