6 FFmpeg4Android：音频解码
音频解码，就是将视频文件中的音频部分抽离出来，生成PCM文件，并使用Android控件AudioTrack进行播放。
新建，MedioPlayer项目，其目录结构如下：
目录结构
java端代码，MainActivity.java：
package com.lzp.decoder;
import java.io.File;
import com.lzp.decoder.view.VideoView;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.Surface;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
public class MainActivity extends Activity {
private Player player;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
player = new Player();
}
public void playAudio(View btn) {
String input = new File(Environment.getExternalStorageDirectory(), "sintel.mp4").getAbsolutePath();
String output = new File(Environment.getExternalStorageDirectory(), "output.pcm").getAbsolutePath();
player.sound(input, output);
}
}
java端代码，Player.java：
package com.lzp.decoder;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.util.Log;
import android.view.Surface;
/**
* 视频播放的控制器
*/
public class Player {
// 解码视频
public native void render(String input, Surface surface);
// 解码音频
public native void sound(String input, String output);
/**
* 创建一个AudioTrac对象，用于播放
*
* @param nb_channels
* @return
*/
public AudioTrack createAudioTrack(int sampleRateInHz, int nb_channels) {
// 固定格式的音频码流
int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
Log.i("jason", "nb_channels:" + nb_channels);
// 声道布局
int channelConfig;
if (nb_channels == 1) {
channelConfig = android.media.AudioFormat.CHANNEL_OUT_MONO;
} else if (nb_channels == 2) {
channelConfig = android.media.AudioFormat.CHANNEL_OUT_STEREO;
} else {
channelConfig = android.media.AudioFormat.CHANNEL_OUT_STEREO;
}
int bufferSizeInBytes = AudioTrack.getMinBufferSize(sampleRateInHz, channelConfig, audioFormat);
AudioTrack audioTrack = new AudioTrack(
AudioManager.STREAM_MUSIC,
sampleRateInHz, channelConfig,
audioFormat,
bufferSizeInBytes, AudioTrack.MODE_STREAM);
// 播放
// audioTrack.play();
// 写入PCM
// audioTrack.write(audioData, offsetInBytes, sizeInBytes);
return audioTrack;
}
static {
System.loadLibrary("avutil-54");
System.loadLibrary("swresample-1");
System.loadLibrary("avcodec-56");
System.loadLibrary("avformat-56");
System.loadLibrary("swscale-3");
System.loadLibrary("postproc-53");
System.loadLibrary("avfilter-5");
System.loadLibrary("avdevice-56");
System.loadLibrary("myffmpeg");
}
}
c端解码代码，ffmpeg_audio_player.c：
#include "com_lzp_decoder_Player.h"
#include
#include
#include
//封装格式
#include "libavformat/avformat.h"
//解码
#include "libavcodec/avcodec.h"
//缩放
#include "libswscale/swscale.h"
//重采样
#include "libswresample/swresample.h"
#define LOGI(FORMAT, ...) __android_log_print(ANDROID_LOG_INFO, "ffmpeg",FORMAT, ##__VA_ARGS__);
#define LOGE(FORMAT, ...) __android_log_print(ANDROID_LOG_ERROR, "ffmpeg",FORMAT, ##__VA_ARGS__);
#define MAX_AUDIO_FRME_SIZE 48000 * 4
JNIEXPORT void JNICALL Java_com_lzp_decoder_Player_sound
(JNIEnv *env, jobject jthiz, jstring input_jstr, jstring output_jstr){
const char* input_cstr = (*env)->GetStringUTFChars(env, input_jstr, NULL);
const char* output_cstr = (*env)->GetStringUTFChars(env, output_jstr, NULL);
LOGI("%s", "sound");
// 注册组件
av_register_all();
AVFormatContext *pFormatCtx = avformat_alloc_context();
//打开音频文件
if (avformat_open_input(&pFormatCtx, input_cstr, NULL, NULL) != 0){
LOGI("无法打开音频文件：%s\n", input_cstr);
return;
}
// 获取输入文件信息
if (avformat_find_stream_info(pFormatCtx, NULL) < 0){
LOGI("%s", "无法获取输入文件信息");
return;
}
// 获取音频流索引位置
int i = 0, audio_stream_idx = -1;
for (; i < pFormatCtx->nb_streams; i++){
if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO){
audio_stream_idx = i;
break;
}
}
// 获取解码器
AVCodecContext *codecCtx = pFormatCtx->streams[audio_stream_idx]->codec;
AVCodec *codec = avcodec_find_decoder(codecCtx->codec_id);
if (codec == NULL){
LOGI("%s", "无法获取解码器");
return;
}
// 打开解码器
if (avcodec_open2(codecCtx, codec, NULL) < 0){
LOGI("%s", "无法打开解码器");
return;
}
// 压缩数据
AVPacket *packet = (AVPacket *)av_malloc(sizeof(AVPacket));
// 解压缩数据
AVFrame *frame = av_frame_alloc();
// frame->16bit 44100 PCM 统一音频采样格式与采样率
SwrContext *swrCtx = swr_alloc();
// 重采样设置参数-------------start
// 输入的采样格式
enum AVSampleFormat in_sample_fmt = codecCtx->sample_fmt;
// 输出采样格式16bit PCM
enum AVSampleFormat out_sample_fmt = AV_SAMPLE_FMT_S16;
// 输入采样率
int in_sample_rate = codecCtx->sample_rate;
// 输出采样率
int out_sample_rate = in_sample_rate;
// 获取输入的声道布局
// 根据声道个数获取默认的声道布局（2个声道，默认立体声stereo）
// av_get_default_channel_layout(codecCtx->channels);
uint64_t in_ch_layout = codecCtx->channel_layout;
// 输出的声道布局（立体声）
uint64_t out_ch_layout = AV_CH_LAYOUT_STEREO;
swr_alloc_set_opts(swrCtx,
out_ch_layout, out_sample_fmt, out_sample_rate,
in_ch_layout, in_sample_fmt, in_sample_rate,
0, NULL);
swr_init(swrCtx);
// 输出的声道个数
int out_channel_nb = av_get_channel_layout_nb_channels(out_ch_layout);
// 重采样设置参数-------------end
// JNI begin------------------
// JasonPlayer
jclass player_class = (*env)->GetObjectClass(env, jthiz);
// AudioTrack对象
jmethodID create_audio_track_mid = (*env)->GetMethodID(env, player_class, "createAudioTrack", "(II)Landroid/media/AudioTrack;");
jobject audio_track = (*env)->CallObjectMethod(env, jthiz, create_audio_track_mid, out_sample_rate, out_channel_nb);
// 调用AudioTrack.play方法
jclass audio_track_class = (*env)->GetObjectClass(env, audio_track);
jmethodID audio_track_play_mid = (*env)->GetMethodID(env, audio_track_class, "play", "()V");
(*env)->CallVoidMethod(env, audio_track, audio_track_play_mid);
// AudioTrack.write
jmethodID audio_track_write_mid = (*env)->GetMethodID(env, audio_track_class, "write", "([BII)I");
// JNI end------------------
FILE *fp_pcm = fopen(output_cstr, "wb");
// 16bit 44100 PCM 数据
uint8_t *out_buffer = (uint8_t *)av_malloc(MAX_AUDIO_FRME_SIZE);
int got_frame = 0, index = 0, ret;
// 不断读取压缩数据
while (av_read_frame(pFormatCtx, packet) >= 0){
// 解码音频类型的Packet
if (packet->stream_index == audio_stream_idx){
// 解码
ret = avcodec_decode_audio4(codecCtx, frame, &got_frame, packet);
if (ret < 0){
LOGI("%s", "解码完成");
}
// 解码一帧成功
if (got_frame > 0){
LOGI("解码：%d", index++);
swr_convert(swrCtx, &out_buffer, MAX_AUDIO_FRME_SIZE, (const uint8_t **)frame->data, frame->nb_samples);
// 获取sample的size
int out_buffer_size = av_samples_get_buffer_size(NULL, out_channel_nb,
frame->nb_samples, out_sample_fmt, 1);
fwrite(out_buffer, 1, out_buffer_size, fp_pcm);
// out_buffer缓冲区数据，转成byte数组
jbyteArray audio_sample_array = (*env)->NewByteArray(env, out_buffer_size);
jbyte* sample_bytep = (*env)->GetByteArrayElements(env, audio_sample_array, NULL);
// out_buffer的数据复制到sampe_bytep
memcpy(sample_bytep, out_buffer, out_buffer_size);
// 同步
(*env)->ReleaseByteArrayElements(env, audio_sample_array, sample_bytep, 0);
// AudioTrack.write PCM数据
(*env)->CallIntMethod(env, audio_track, audio_track_write_mid,
audio_sample_array, 0, out_buffer_size);
// 释放局部引用
(*env)->DeleteLocalRef(env, audio_sample_array);
usleep(1000 * 16);
}
}
av_free_packet(packet);
}
av_frame_free(&frame);
av_free(out_buffer);
swr_free(&swrCtx);
avcodec_close(codecCtx);
avformat_close_input(&pFormatCtx);
(*env)->ReleaseStringUTFChars(env, input_jstr, input_cstr);
(*env)->ReleaseStringUTFChars(env, output_jstr, output_cstr);
}
运行结果日志：
运行结果
源码+视频文件下载：http://download.csdn.net/download/itismelzp/10229694