在native层中，使用AMediaCodec 和 AMediaMuxer 编码生成MP4文件的demo

好的，我可以为您提供一个简单的使用AMediaCodec和AMediaMuxer编码生成MP4文件的示例代码。示例代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <media/NdkMediaCodec.h>
#include <media/NdkMediaFormat.h>
#include <media/NdkMediaMuxer.h>

#define MAX_SAMPLE_SIZE (1024 * 1024)
#define TIMEOUT_USEC 10000

int main(int argc, char **argv) {
    const char *path = "/sdcard/output.mp4";
    int fd = open(path, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
    if (fd < 0) {
        printf("open file failed\n");
        return -1;
    }

    AMediaMuxer *muxer = AMediaMuxer_new(fd, AMEDIAMUXER_OUTPUT_FORMAT_MPEG_4);
    if (!muxer) {
        printf("create muxer failed\n");
        return -1;
    }

    AMediaFormat *format = AMediaFormat_new();
    AMediaFormat_setString(format, AMEDIAFORMAT_KEY_MIME, "video/avc");
    AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_WIDTH, 1280);
    AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_HEIGHT, 720);
    AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_BIT_RATE, 2000000);
    AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_FRAME_RATE, 30);
    AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_I_FRAME_INTERVAL, 1);

    AMediaCodec *encoder = AMediaCodec_createEncoderByType("video/avc");
    if (!encoder) {
        printf("create encoder failed\n");
        return -1;
    }

    AMediaCodec_configure(encoder, format, NULL, NULL, AMEDIACODEC_CONFIGURE_FLAG_ENCODE);
    AMediaCodec_start(encoder);

    uint8_t *input_data = NULL;
    AMediaCodecBufferInfo input_info;
    uint8_t *output_data = NULL;
    AMediaCodecBufferInfo output_info;
    bool input_done = false;
    bool output_done = false;
    int64_t time_us = 0;

    while (!output_done) {
        if (!input_done) {
            int input_index = AMediaCodec_dequeueInputBuffer(encoder, TIMEOUT_USEC);
            if (input_index >= 0) {
                input_data = AMediaCodec_getInputBuffer(encoder, input_index, NULL);
                ssize_t sample_size = read(STDIN_FILENO, input_data, MAX_SAMPLE_SIZE);
                if (sample_size < 0) {
                    printf("read data failed\n");
                    break;
                }
                input_done = (sample_size == 0);
                if (input_done) {
                    AMediaCodec_queueInputBuffer(encoder, input_index, 0, 0, time_us, AMEDIACODEC_BUFFER_FLAG_END_OF_STREAM);
                } else {
                    AMediaCodec_queueInputBuffer(encoder, input_index, 0, sample_size, time_us, 0);
                }
                time_us += 1000000 / 30;
            }
        }

        ssize_t output_index = AMediaCodec_dequeueOutputBuffer(encoder, &output_info, TIMEOUT_USEC);
        if (output_index == AMEDIACODEC_INFO_TRY_AGAIN_LATER) {
            continue;
        } else if (output_index == AMEDIACODEC_INFO_OUTPUT_FORMAT_CHANGED) {
            AMediaFormat *output_format = NULL;
            output_format = AMediaCodec_getOutputFormat(encoder);
            AMediaMuxer_addTrack(muxer, output_format);
            AMediaMuxer_start(muxer);
        } else if (output_index == AMEDIACODEC_INFO_OUTPUT_BUFFERS_CHANGED) {
            // do nothing
        } else if (output_index < 0) {
            printf("unexpected result from encoder\n");
            break;
        } else {
            output_data = AMediaCodec_getOutputBuffer(encoder, output_index, NULL);
            AMediaMuxer_writeSampleData(muxer, 0, output_data, &output_info);
            AMediaCodec_releaseOutputBuffer(encoder, output_index, false);
            output_done = (output_info.flags & AMEDIACODEC_BUFFER_FLAG_END_OF_STREAM) != 0;
        }
    }

    AMediaCodec_stop(encoder);
    AMediaCodec_delete(encoder);
    AMediaFormat_delete(format);
    AMediaMuxer_stop(muxer);
    AMediaMuxer_delete(muxer);
    close(fd);

    return 0;
}

这个示例代码将从标准输入中读取h264裸流，并使用AMediaCodec和AMediaMuxer进行编码和封装成MP4文件。您可以将其编译成可执行文件并在Android设备上运行。注意，在运行前请确保您已经打开了摄像头权限并且已经有h264裸流数据输入到标准输入中。