MediaCodec通过C++ 解码MP4视频完整代码例子

以下是一个简单的示例代码，展示了如何使用MediaCodec解码MP4视频文件。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#include <media/NdkMediaCodec.h>
#include <media/NdkMediaExtractor.h>
#include <media/NdkMediaFormat.h>

#define VIDEO_WIDTH 640
#define VIDEO_HEIGHT 480
#define VIDEO_FRAMERATE 30
#define VIDEO_BITRATE 2000000

#define MP4_FILE "/sdcard/test.mp4"

int main(int argc, char** argv) {
    AMediaExtractor* extractor = AMediaExtractor_new();
    AMediaExtractor_setDataSource(extractor, MP4_FILE);

    int track_count = AMediaExtractor_getTrackCount(extractor);
    AMediaFormat* format = NULL;
    int video_track_index = -1;

    for (int i = 0; i < track_count; i++) {
        format = AMediaExtractor_getTrackFormat(extractor, i);
        const char* mime_type = NULL;
        AMediaFormat_getString(format, AMEDIAFORMAT_KEY_MIME, &mime_type);
        if (!strncmp(mime_type, "video/", 6)) {
            video_track_index = i;
            break;
        }
    }

    if (video_track_index == -1) {
        printf("No video track found in %s\n", MP4_FILE);
        return -1;
    }

    AMediaExtractor_selectTrack(extractor, video_track_index);

    AMediaCodec* codec = AMediaCodec_createDecoderByType(mime_type);
    AMediaCodec_configure(codec, format, NULL, NULL, 0);

    AMediaCodec_start(codec);

    AMediaCodecBufferInfo buffer_info;
    ssize_t sample_size = 0;
    uint8_t* input_buffer = NULL;
    uint8_t* output_buffer = NULL;
    size_t input_buffer_size = 0;
    size_t output_buffer_size = 0;

    while (true) {
        sample_size = AMediaExtractor_readSampleData(extractor, input_buffer, input_buffer_size);
        if (sample_size < 0) {
            break;
        }

        int flags = AMediaExtractor_getSampleFlags(extractor);
        int64_t presentation_time_us = AMediaExtractor_getSampleTime(extractor);

        int input_buffer_index = AMediaCodec_dequeueInputBuffer(codec, -1);
        if (input_buffer_index >= 0) {
            input_buffer = AMediaCodec_getInputBuffer(codec, input_buffer_index, &input_buffer_size);
            memcpy(input_buffer, input_buffer, sample_size);

            AMediaCodec_queueInputBuffer(codec, input_buffer_index, 0, sample_size, presentation_time_us, flags);

            AMediaExtractor_advance(extractor);
        }

        int output_buffer_index = AMediaCodec_dequeueOutputBuffer(codec, &buffer_info, -1);
        if (output_buffer_index >= 0) {
            output_buffer = AMediaCodec_getOutputBuffer(codec, output_buffer_index, &output_buffer_size);
            AMediaCodec_releaseOutputBuffer(codec, output_buffer_index, true);
        }
    }

    AMediaCodec_stop(codec);
    AMediaCodec_delete(codec);
    AMediaExtractor_delete(extractor);

    return 0;
}

这个示例代码使用了Android NDK中的MediaCodec API，可以在Android平台上运行。它首先通过MediaExtractor获取到视频轨道信息，然后创建一个解码器，将视频轨道的MIME类型传递给解码器，配置解码器参数，启动解码器，循环从输入流中读取数据，将数据传递给解码器进行解码，获取解码后的数据并处理。