MediaCodec通过C++将MP4解码成yuv例子

以下是一个简单的示例，展示了如何使用MediaCodec API将MP4文件解码为YUV格式：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <android/native_window.h>
#include <media/NdkMediaCodec.h>
#include <media/NdkMediaExtractor.h>
#include <media/NdkMediaFormat.h>

#define OUTPUT_YUV_FILE "/sdcard/output.yuv"
#define MAX_BUF_SIZE 0x400000

int main(int argc, char* argv[]) {
    AMediaExtractor *extractor = NULL;
    AMediaCodec *codec = NULL;
    AMediaFormat *inputFormat = NULL, *outputFormat = NULL;
    ANativeWindow* window = NULL;
    uint8_t *inputBuf = NULL, *outputBuf = NULL;
    ssize_t bufSize, sampleSize;
    size_t inputIdx, outputIdx, outputOffset, outputSize;
    uint32_t flags;
    int fd, ret, i;
    off_t offset;
    const char* mime;
    void* codecBuf = NULL;

    // 打开MP4文件
    fd = open(argv[1], O_RDONLY);
    if (fd < 0) {
        printf("open %s failed, ret=%d\n", argv[1], fd);
        return -1;
    }

    // 使用MediaExtractor API读取视频信息
    extractor = AMediaExtractor_new();
    ret = AMediaExtractor_setDataSourceFd(extractor, fd, 0, MAX_BUF_SIZE);
    if (ret != AMEDIA_OK) {
        printf("setDataSource failed, ret=%d\n", ret);
        goto error;
    }

    // 获取视频的格式信息
    inputFormat = AMediaExtractor_getTrackFormat(extractor, 0);
    mime = AMediaFormat_toString(inputFormat);
    printf("input format : %s\n", mime);

    // 创建MediaCodec解码器
    codec = AMediaCodec_createDecoderByType(mime);
    if (codec == NULL) {
        printf("createDecoderByType failed\n");
        goto error;
    }

    // 配置解码器
    ret = AMediaCodec_configure(codec, inputFormat, NULL, NULL, 0);
    if (ret != AMEDIA_OK) {
        printf("configure failed, ret=%d\n", ret);
        goto error;
    }

    // 启动解码器
    ret = AMediaCodec_start(codec);
    if (ret != AMEDIA_OK) {
        printf("start failed, ret=%d\n", ret);
        goto error;
    }

    // 获取解码器的输出格式信息
    outputFormat = AMediaCodec_getOutputFormat(codec);
    mime = AMediaFormat_toString(outputFormat);
    printf("output format : %s\n", mime);

    // 打开输出文件
    int outFd = open(OUTPUT_YUV_FILE, O_CREAT | O_TRUNC | O_WRONLY, 0666);
    if (outFd < 0) {
        printf("open %s failed, ret=%d\n", OUTPUT_YUV_FILE, outFd);
        goto error;
    }

    // 分配解码器输入和输出缓冲区
    bufSize = AMediaFormat_getInt32(inputFormat, AMEDIAFORMAT_KEY_MAX_INPUT_SIZE);
    inputBuf = (uint8_t*)malloc(bufSize);
    outputBuf = (uint8_t*)malloc(bufSize * 4);
    codecBuf = AMediaCodec_getInputBuffer(codec, 0, &bufSize);

    // 循环读取视频帧并解码
    inputIdx = outputIdx = 0;
    flags = 0;

    while (true) {
        // 读取视频帧
        sampleSize = AMediaExtractor_readSampleData(extractor, inputBuf, bufSize);
        if (sampleSize < 0) {
            printf("read sample data failed, ret=%d\n", sampleSize);
            break;
        }

        // 将视频帧送入解码器
        inputIdx = AMediaCodec_dequeueInputBuffer(codec, 10000);
        if (inputIdx >= 0) {
            memcpy(codecBuf, inputBuf, sampleSize);
            AMediaCodec_queueInputBuffer(codec, inputIdx, 0, sampleSize, 0, flags);
            AMediaExtractor_advance(extractor);
        }

        // 获取解码器的输出数据
        outputIdx = AMediaCodec_dequeueOutputBuffer(codec, NULL, 10000);
        if (outputIdx == AMEDIACODEC_INFO_OUTPUT_FORMAT_CHANGED) {
            printf("output format changed\n");
            outputFormat = AMediaCodec_getOutputFormat(codec);
            mime = AMediaFormat_toString(outputFormat);
            printf("output format : %s\n", mime);
        } else if (outputIdx >= 0) {
            // 获取输出数据的偏移量和大小
            AMediaCodecBufferInfo bufferInfo;
            AMediaCodec_getOutputBufferInfo(codec, &bufferInfo, outputIdx);
            outputOffset = bufferInfo.offset;
            outputSize = bufferInfo.size;

            // 读取输出数据
            ret = AMediaCodec_getOutputBufferData(codec, outputIdx, &outputBuf[outputOffset], outputSize);
            if (ret != AMEDIA_OK) {
                printf("getOutputBufferData failed, ret=%d\n", ret);
                break;
            }

            // 将YUV数据写入文件
            write(outFd, outputBuf, outputSize);

            // 释放输出缓冲区
            AMediaCodec_releaseOutputBuffer(codec, outputIdx, false);
        } else if (outputIdx == AMEDIACODEC_INFO_TRY_AGAIN_LATER) {
            // do nothing
        } else if (outputIdx == AMEDIACODEC_INFO_OUTPUT_BUFFERS_CHANGED) {
            // do nothing
        } else {
            printf("dequeueOutputBuffer failed, ret=%d\n", outputIdx);
            break;
        }
    }

    // 停止解码器
    AMediaCodec_stop(codec);

    // 释放资源
    free(inputBuf);
    free(outputBuf);
    close(outFd);
    AMediaCodec_delete(codec);
    AMediaExtractor_delete(extractor);
    close(fd);
    return 0;

error:
    if (inputBuf) free(inputBuf);
    if (outputBuf) free(outputBuf);
    if (codec) AMediaCodec_delete(codec);
    if (extractor) AMediaExtractor_delete(extractor);
    if (fd >= 0) close(fd);
    if (outFd >= 0) close(outFd);
    return -1;
}

这个示例使用`AMediaExtractor` API从MP4文件中读取视频信息，然后使用`AMediaCodec` API进行解码。在循环中，它读取一帧视频，将其送入解码器，然后从解码器中获取输出YUV数据，将其写入文件中。最后，它停止解码器并释放所有资源。请注意，这个示例仅仅是一个简单的示例，你可能需要根据自己的需求修改它。