android下初步使用ffmpeg

            接着暑做的一个项目就是在Android下做一个播放器，考虑到编码和解码的问题我们，目前采用的是使用ffmpeg这个开源库（在Android平台下可以实现移植），这个开源库由于是开源的，它的注释很是详细，但是我们这等人居然还是不太懂怎么用，于是我就看了下网上的一些例子，改了一个程序，希望对大家有所帮助：

     其实我的目的很简单就是实现mp3转化为pcm的，这这个pcm数据存放到一个文件中。

      其他的不说了我就先上代码：

#include <string.h>#include <jni.h>#include <android/log.h>#include <ffmpeg/libavcodec/avcodec.h>#include <ffmpeg/libavformat/avformat.h>#include <ffmpeg/libswscale/swscale.h>#include <string.h>#define LOG_TAG    "***************************lixingyun*****************" // 这个是自定义的LOG的标识#undef LOG // 取消默认的LOG#define LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__) // 定义LOG类型#define LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__) // 定义LOG类型#define LOGW(...)  __android_log_print(ANDROID_LOG_WARN,LOG_TAG,__VA_ARGS__) // 定义LOG类型#define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__) // 定义LOG类型#define LOGF(...)  __android_log_print(ANDROID_LOG_FATAL,LOG_TAG,__VA_ARGS__) // 定义LOG类型/* This is a trivial JNI example where we use a native method * to return a new VM String. See the corresponding Java source * file located at: * *   apps/samples/hello-jni/project/src/com/example/HelloJni/HelloJni.java */JNIEXPORT jstring Java_com_example_hellojni_HelloJni_stringFromJNI(JNIEnv* env,jobject thiz) {char str[25];sprintf(str, "%d", avcodec_version());return (*env)->NewStringUTF(env, str);// return (*env)->NewStringUTF(env, "Hello from JNI !");0}JNIEXPORT jint Java_com_example_hellojni_HelloJni_getVoice(JNIEnv* env,jobject thiz) {const char *filename = "file:/sdcard/test.mp3";const char *outFielName = "/mnt/sdcard/ffmpeg.txt";AVFormatContext *pFormatCtx = NULL;AVCodecContext *pCodecCtx = NULL;AVCodec *aaccodec = NULL;AVPacket aacpkt;int len = 0;int size = 0;unsigned char *outbuf = NULL;// unsigned char inbuf[INBUF_SIZE*5],*inbuf_ptr;int outsize;int newpacket = 0;int audio_stream = -1;int out_ape_fp = -1;int in_ape_fp = -1;double start_time = 0;double duration = 0;FILE *out_fp;const unsigned char start_code[4] = { 0x00, 0x00, 0x00, 0x01 };out_fp = fopen(outFielName, "wb+");// memset(inbuf, 0, sizeof(inbuf));// inbuf_ptr = inbuf;aacpkt.data = NULL;aacpkt.size = 0;av_init_packet(&aacpkt);//if (argc < 2) {//printf("Usage: test <file>\n");//exit(1);//}// Register all formats and codecsav_register_all();// Open video fileif (av_open_input_file(&pFormatCtx, filename, NULL, 0, NULL) != 0){  LOGE("av_open_input_file error\n");  return -1; // Couldn't open file}// Retrieve stream informationif (av_find_stream_info(pFormatCtx) < 0)return -1; // Couldn't find stream information// Dump information about file onto standard errordump_format(pFormatCtx, 0, filename, 0);int i= 0;for (i = 0; i < pFormatCtx->nb_streams; i++) {if (pFormatCtx->streams[i]->codec->codec_type == CODEC_TYPE_AUDIO) {audio_stream = i;break;}}if (audio_stream == -1) {printf("audio not found!\n");return -1;} else {pCodecCtx = pFormatCtx->streams[audio_stream]->codec;aaccodec = avcodec_find_decoder(pCodecCtx->codec_id);if (aaccodec == NULL)return -1;if (avcodec_open(pCodecCtx, aaccodec) < 0)return -1;}LOGI(" bit_rate = %d \r\n", pCodecCtx->bit_rate);    LOGI(" sample_rate = %d \r\n", pCodecCtx->sample_rate);    LOGI(" channels = %d \r\n", pCodecCtx->channels);    LOGI(" code_name = %s \r\n", pCodecCtx->codec->name);    //LOGI("extra data size: %d :data%x %x %x %x\n",pInCodecCtx->extradata_size,pInCodecCtx->extradata[0]    // ,pInCodecCtx->extradata[1],pInCodecCtx->extradata[2],pInCodecCtx->extradata[3]);    LOGI(" block_align = %d\n", pCodecCtx->block_align);outbuf = (unsigned char *) malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE * 2);outsize = AVCODEC_MAX_AUDIO_FRAME_SIZE * 2;while (av_read_frame(pFormatCtx, &aacpkt) >= 0) {if (aacpkt.stream_index == audio_stream) {int declen = 0;size = aacpkt.size;while (aacpkt.size > 0) {outsize = AVCODEC_MAX_AUDIO_FRAME_SIZE * 2;memset(outbuf, 0, outsize);len = avcodec_decode_audio3(pCodecCtx, (int16_t *) outbuf,&outsize, &aacpkt);if (len < 0) {printf("avcodec_decode_audio3 failed!\n");break;}if (outsize > 0) {fwrite(outbuf, 1, outsize, out_fp);printf("write %d bytes\n", outsize);}declen += len;if (declen == size) {av_free_packet(&aacpkt);printf("packet decoded succeed!\n");break;} else if (declen < size) {aacpkt.size -= len;aacpkt.data += len;} else {printf("decode error!\n");break;}}}}fclose(out_fp);// Close the codecavcodec_close(pCodecCtx);// Close the video fileav_close_input_file(pFormatCtx);return 0;}

这个