Android本地视频播放器开发--ffmpeg解码视频文件中的音频(1)

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 libraryinclude $(CLEAR_VARS)LOCAL_MODULE := ffmpeg-prebuiltLOCAL_SRC_FILES := ffmpeg/android/armv7-a/libffmpeg-neon.soLOCAL_EXPORT_C_INCLUDES := ffmpeg/android/armv7-a/includeLOCAL_EXPORT_LDLIBS := ffmpeg/android/armv7-a/libffmpeg-neon.soLOCAL_PRELINK_MODULE := trueinclude $(PREBUILT_SHARED_LIBRARY)##########################################################              ffmpeg-test-neno.so             ################################################################include $(CLEAR_VARS)TARGET_ARCH_ABI=armeabi-v7aLOCAL_ARM_MODE=armLOCAL_ARM_NEON=trueLOCAL_ALLOW_UNDEFINED_SYMBOLS=falseLOCAL_MODULE := ffmpeg-test-neonLOCAL_SRC_FILES := jniffmpeg/Decodec_Audio.cLOCAL_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-prebuiltLOCAL_LDLIBS    := -llog -ljnigraphics -lz -lm $(LOCAL_PATH)/ffmpeg/android/armv7-a/libffmpeg-neon.soinclude $(BUILD_SHARED_LIBRARY)

然后在终端运行ndk-build,运行结果如下:

root@zhangjie:/Graduation/jni# ndk-buildInstall        : libffmpeg-neon.so => libs/armeabi/libffmpeg-neon.soCompile arm    : ffmpeg-test-neon <= Decodec_Audio.cSharedLibrary  : libffmpeg-test-neon.soInstall        : libffmpeg-test-neon.so => libs/armeabi/libffmpeg-test-neon.so

把编译出来的

libffmpeg-test-neon.solibffmpeg-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  :204806-07 04:51:31.000: I/graduation(7014): audioDecodec  :204806-07 04:51:31.109: I/graduation(7014): audioDecodec  :204806-07 04:51:31.156: I/graduation(7014): audioDecodec  :204806-07 04:51:31.257: I/graduation(7014): audioDecodec  :204806-07 04:51:31.304: I/graduation(7014): audioDecodec  :204806-07 04:51:31.406: I/graduation(7014): audioDecodec  :204806-07 04:51:31.460: I/graduation(7014): audioDecodec  :204806-07 04:51:31.554: I/graduation(7014): audioDecodec  :204806-07 04:51:31.609: I/graduation(7014): audioDecodec  :204806-07 04:51:31.710: I/graduation(7014): audioDecodec  :204806-07 04:51:31.757: I/graduation(7014): audioDecodec  :204806-07 04:51:31.859: I/graduation(7014): audioDecodec  :204806-07 04:51:31.914: I/graduation(7014): audioDecodec  :204806-07 04:51:32.015: I/graduation(7014): audioDecodec  :204806-07 04:51:32.062: I/graduation(7014): audioDecodec  :204806-07 04:51:32.164: I/graduation(7014): audioDecodec  :204806-07 04:51:32.210: I/graduation(7014): audioDecodec  :204806-07 04:51:32.312: I/graduation(7014): audioDecodec  :204806-07 04:51:32.367: I/graduation(7014): audioDecodec  :204806-07 04:51:32.468: I/graduation(7014): audioDecodec  :204806-07 04:51:32.515: I/graduation(7014): audioDecodec  :204806-07 04:51:32.617: I/graduation(7014): audioDecodec  :204806-07 04:51:32.671: I/graduation(7014): audioDecodec  :204806-07 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。

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