在上一章中Android本地视频播放器开发--NDK编译FFmpeg能够获取编译出来的ffmpeg库，接下来就是调用ffmpeg来实现解码，这里我们先解码音频，然后在播放音频，同时为了适应性我会用不同的方法进行播放例如使用Android提供的AudioTrack，SDL、OpengAL,OpenSL ES，最终合入视频播放器的是OpenSL ES，这样可以减少CPU的利用率。接下来在这一章中，先简单的介绍如何解码音频，在下一章中，实现音频的播放。
首先就是编写调用ffmpeg的文件这里命名为:Decodec_Audio.c
#include <stdio.h>
#include <stdlib.h>
#include <android/log.h>
#include "VideoPlayerDecode.h"
#include "../ffmpeg/libavutil/avutil.h"
#include "../ffmpeg/libavcodec/avcodec.h"
#include "../ffmpeg/libavformat/avformat.h"
#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "graduation", __VA_ARGS__))
AVFormatContext *pFormatCtx = NULL;
int audioStream, delay_time, videoFlag = 0;
AVCodecContext *aCodecCtx;
AVCodec *aCodec;
AVFrame *aFrame;
AVPacket packet;
int frameFinished = 0;
JNIEXPORT jint JNICALL Java_com_zhangjie_graduation_videopalyer_jni_VideoPlayerDecode_VideoPlayer
(JNIEnv *env, jclass clz, jstring fileName)
{
const char* local_title = (*env)->GetStringUTFChars(env, fileName, NULL);
av_register_all();//注册所有支持的文件格式以及编解码器
/*
*只读取文件头，并不会填充流信息
*/
if(avformat_open_input(&pFormatCtx, local_title, NULL, NULL) != 0)
return -1;
/*
*获取文件中的流信息，此函数会读取packet，并确定文件中所有流信息，
*设置pFormatCtx->streams指向文件中的流，但此函数并不会改变文件指针，
*读取的packet会给后面的解码进行处理。
*/
if(avformat_find_stream_info(pFormatCtx, NULL) < 0)
return -1;
/*
*输出文件的信息，也就是我们在使用ffmpeg时能够看到的文件详细信息，
*第二个参数指定输出哪条流的信息，-1代表ffmpeg自己选择。最后一个参数用于
*指定dump的是不是输出文件，我们的dump是输入文件，因此一定要为0
*/
av_dump_format(pFormatCtx, -1, local_title, 0);
int i = 0;
for(i=0; i< pFormatCtx->nb_streams; i++)
{
if(pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO){
audioStream = i;
break;
}
}
if(audioStream < 0)return -1;
aCodecCtx = pFormatCtx->streams[audioStream]->codec;
aCodec = avcodec_find_decoder(aCodecCtx->codec_id);
if(avcodec_open2(aCodecCtx, aCodec, NULL) < 0)return -1;
aFrame = avcodec_alloc_frame();
if(aFrame == NULL)return -1;
int ret;
while(videoFlag != -1)
{
if(av_read_frame(pFormatCtx, &packet) < 0)break;
if(packet.stream_index == audioStream)
{
ret = avcodec_decode_audio4(aCodecCtx, aFrame, &frameFinished, &packet);
if(ret > 0 && frameFinished)
{
int data_size = av_samples_get_buffer_size(
aFrame->linesize,aCodecCtx->channels,
aFrame->nb_samples,aCodecCtx->sample_fmt, 0);
LOGI("audioDecodec :%d",data_size);
}
}
usleep(50000);
while(videoFlag != 0)
{
if(videoFlag == 1)//暂停
{
sleep(1);
}else if(videoFlag == -1) //停止
{
break;
}
}
av_free_packet(&packet);
}
av_free(aFrame);
avcodec_close(aCodecCtx);
avformat_close_input(&pFormatCtx);
(*env)->ReleaseStringUTFChars(env, fileName, local_title);
}
JNIEXPORT jint JNICALL Java_com_zhangjie_graduation_videopalyer_jni_VideoPlayerDecode_VideoPlayerPauseOrPlay
(JNIEnv *env, jclass clz)
{
if(videoFlag == 1)
{
videoFlag = 0;
}else if(videoFlag == 0){
videoFlag = 1;
}
return videoFlag;
}
JNIEXPORT jint JNICALL Java_com_zhangjie_graduation_videopalyer_jni_VideoPlayerDecode_VideoPlayerStop
(JNIEnv *env, jclass clz)
{
videoFlag = -1;
}
接下来就是编写Android.mk:
#######################################################
########## ffmpeg-prebuilt #######
#######################################################
#declare the prebuilt library
include $(CLEAR_VARS)
LOCAL_MODULE := ffmpeg-prebuilt
LOCAL_SRC_FILES := ffmpeg/android/armv7-a/libffmpeg-neon.so
LOCAL_EXPORT_C_INCLUDES := ffmpeg/android/armv7-a/include
LOCAL_EXPORT_LDLIBS := ffmpeg/android/armv7-a/libffmpeg-neon.so
LOCAL_PRELINK_MODULE := true
include $(PREBUILT_SHARED_LIBRARY)
########################################################
## ffmpeg-test-neno.so ########
########################################################
include $(CLEAR_VARS)
TARGET_ARCH_ABI=armeabi-v7a
LOCAL_ARM_MODE=arm
LOCAL_ARM_NEON=true
LOCAL_ALLOW_UNDEFINED_SYMBOLS=false
LOCAL_MODULE := ffmpeg-test-neon
LOCAL_SRC_FILES := jniffmpeg/Decodec_Audio.c
LOCAL_C_INCLUDES := $(LOCAL_PATH)/ffmpeg/android/armv7-a/include \
$(LOCAL_PATH)/ffmpeg \
$(LOCAL_PATH)/ffmpeg/libavutil \
$(LOCAL_PATH)/ffmpeg/libavcodec \
$(LOCAL_PATH)/ffmpeg/libavformat \
$(LOCAL_PATH)/ffmpeg/libavcodec \
$(LOCAL_PATH)/ffmpeg/libswscale \
$(LOCAL_PATH)/jniffmpeg \
$(LOCAL_PATH)
LOCAL_SHARED_LIBRARY := ffmpeg-prebuilt
LOCAL_LDLIBS := -llog -ljnigraphics -lz -lm $(LOCAL_PATH)/ffmpeg/android/armv7-a/libffmpeg-neon.so
include $(BUILD_SHARED_LIBRARY)
然后在终端运行ndk-build,运行结果如下:
root@zhangjie:/Graduation/jni# ndk-build Install : libffmpeg-neon.so => libs/armeabi/libffmpeg-neon.so Compile arm : ffmpeg-test-neon <= Decodec_Audio.c SharedLibrary : libffmpeg-test-neon.so Install : libffmpeg-test-neon.so => libs/armeabi/libffmpeg-test-neon.so
把编译出来的
libffmpeg-test-neon.so
libffmpeg-neon.so
拷贝到之前android功能下的libs/armeabi目录下面，点击视频，视频文件开始解码音频，当解码成功，则打印出解码音频包的大小：
06-07 04:51:30.953: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.000: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.109: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.156: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.257: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.304: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.406: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.460: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.554: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.609: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.710: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.757: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.859: I/graduation(7014): audioDecodec :2048 06-07 04:51:31.914: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.015: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.062: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.164: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.210: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.312: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.367: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.468: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.515: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.617: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.671: I/graduation(7014): audioDecodec :2048 06-07 04:51:32.773: I/graduation(7014): audioDecodec :2048
在logcat里面可以看到解码音频成功，下面一章我们将解码出来的音频进行播放。