本文记录另一个安卓平台下基于FFmpeg的视频解码器。与前一篇文章记录的解码器不同，本文记录的解码器不再使用libavcodec.so、libavformat.so等类库，而只使用了一个类库——libffmpeg.so。该视频解码器C语言的源代码来自于《最简单的基于FFMPEG+SDL的视频播放器》。相关的概念就不再重复记录了。FFmpeg类库的打包记录一下FFmpeg类库打包的方法。Android平台下FFmpeg类库一共包含下面几个：libavformat-56.solibavcodec-56.solibavfilter-5.solibavdevice-56.solibavutil-54.solibpostproc-53.solibswresample-1.solibswscale-3.so由于数目繁多，直接使用这些类库还是比较麻烦的。因此可以将它们合并为一个类库。具体打包的命令就是下面脚本中“make install”后面的那个命令。cd ffmpegmake cleanexport NDK=/home/leixiaohua1020/cdtworkspace/android-ndk-r9dexport PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.8/prebuiltexport PLATFORM=$NDK/platforms/android-8/arch-armexport PREFIX=../ff-pure-onelibbuild_one(){ ./configure –target-os=linux –prefix=$PREFIX \–enable-cross-compile \–enable-runtime-cpudetect \–disable-asm \–arch=arm \–cc=$PREBUILT/linux-x86_64/bin/arm-linux-androideabi-gcc \–cross-prefix=$PREBUILT/linux-x86_64/bin/arm-linux-androideabi- \–disable-stripping \–nm=$PREBUILT/linux-x86_64/bin/arm-linux-androideabi-nm \–sysroot=$PLATFORM \–enable-gpl –enable-static –disable-shared –enable-nonfree –enable-version3 –enable-small \–enable-zlib –disable-ffprobe –disable-ffplay –disable-ffmpeg –disable-ffserver –disable-debug \–extra-cflags="-fPIC -DANDROID -D__thumb__ -mthumb -Wfatal-errors -Wno-deprecated -mfloat-abi=softfp -marm -march=armv7-a" }build_onemakemake install$PREBUILT/linux-x86_64/bin/arm-linux-androideabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -L$PREFIX/lib -soname libffmpeg.so -shared -nostdlib -Bsymbolic –whole-archive –no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavfilter/libavfilter.a libswresample/libswresample.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a libpostproc/libpostproc.a libavdevice/libavdevice.a -lc -lm -lz -ldl -llog –dynamic-linker=/system/bin/linker $PREBUILT/linux-x86_64/lib/gcc/arm-linux-androideabi/4.8/libgcc.acd ..
需要注意：
（1）与前面记录的脚本不同，这个脚本不再需要修改Configure的内容（生成的是*.a而不是*.so，并没有涉及到版本号问题）。
（2）前文记录的脚本里面Configure的时候是“–enable-shared –disable-static”，这个脚本里面Configure的时候设置的是“–enable-static –disable-shared”。编译完成后生成的是：
libavcodec.a
libavfilter.a
libswresample.a
libavformat.a
libavutil.a
libswscale.a
libpostproc.a
libavdevice.a
该脚本运行完后，会把上述的*.a文件打包为1个*.so文件：
libffmpeg.so
合并后的类库使用起来和合并前的类库使用方法没有区别。
源代码项目的目录结构如图所示。Java源代码位于src目录，而C代码位于jni目录。
Android程序Java端代码位于src\com\leixiaohua1020\sffmpegandroiddecoder\MainActivity.java，如下所示。/** * 最简单的基于FFmpeg的视频解码器-安卓 – 单库版 * Simplest FFmpeg Android Decoder – One Library * * 雷霄骅 Lei Xiaohua * leixiaohua1020@126.com * 中国传媒大学/数字电视技术 * Communication University of China / Digital TV Technology * * * 本程序是安卓平台下最简单的基于FFmpeg的视频解码器。 * 它可以将输入的视频数据解码成YUV像素数据。 * * This software is the simplest decoder based on FFmpeg in Android. * It can decode video stream to raw YUV data. * */package com.leixiaohua1020.sffmpegandroiddecoder;import android.os.Bundle;import android.os.Environment;import android.app.Activity;import android.text.Editable;import android.util.Log;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button startButton = (Button) this.findViewById(R.id.button_start);final EditText urlEdittext_input= (EditText) this.findViewById(R.id.input_url);final EditText urlEdittext_output= (EditText) this.findViewById(R.id.output_url);startButton.setOnClickListener(new OnClickListener() {public void onClick(View arg0){String folderurl=Environment.getExternalStorageDirectory().getPath();String urltext_input=urlEdittext_input.getText().toString();String inputurl=folderurl+"/"+urltext_input;String urltext_output=urlEdittext_output.getText().toString();String outputurl=folderurl+"/"+urltext_output;Log.i("inputurl",inputurl);Log.i("outputurl",outputurl);decode(inputurl,outputurl);}});}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}//JNIpublic native int decode(String inputurl, String outputurl);static{System.loadLibrary("ffmpeg");System.loadLibrary("sffdecoder");}}C语言端源代码位于jni/simplest_ffmpeg_decoder.c，如下所示。/** * 最简单的基于FFmpeg的视频解码器-安卓 – 单库版 * Simplest FFmpeg Android Decoder – One Library * * 雷霄骅 Lei Xiaohua * leixiaohua1020@126.com * 中国传媒大学/数字电视技术 * Communication University of China / Digital TV Technology * * * 本程序是安卓平台下最简单的基于FFmpeg的视频解码器。 * 它可以将输入的视频数据解码成YUV像素数据。 * * This software is the simplest decoder based on FFmpeg in Android. * It can decode video stream to raw YUV data. * */#include <stdio.h>#include <time.h> #include "libavcodec/avcodec.h"#include "libavformat/avformat.h"#include "libswscale/swscale.h"#include "libavutil/log.h"#ifdef ANDROID#include <jni.h>#include <android/log.h>#define LOGE(format, …) __android_log_print(ANDROID_LOG_ERROR, "(>_<)", format, ##__VA_ARGS__)#define LOGI(format, …) __android_log_print(ANDROID_LOG_INFO, "(=_=)", format, ##__VA_ARGS__)#else#define LOGE(format, …) printf("(>_<) " format "\n", ##__VA_ARGS__)#define LOGI(format, …) printf("(^_^) " format "\n", ##__VA_ARGS__)#endif//Output FFmpeg’s av_log()void custom_log(void *ptr, int level, const char* fmt, va_list vl){FILE *fp=fopen("/storage/emulated/0/av_log.txt","a+");if(fp){vfprintf(fp,fmt,vl);fflush(fp);fclose(fp);}}JNIEXPORT jint JNICALL Java_com_leixiaohua1020_sffmpegandroiddecoder_MainActivity_decode (JNIEnv *env, jobject obj, jstring input_jstr, jstring output_jstr){AVFormatContext*pFormatCtx;inti, videoindex;AVCodecContext*pCodecCtx;AVCodec*pCodec;AVFrame*pFrame,*pFrameYUV;uint8_t *out_buffer;AVPacket *packet;int y_size;int ret, got_picture;struct SwsContext *img_convert_ctx;FILE *fp_yuv;int frame_cnt;clock_t time_start, time_finish;double time_duration = 0.0;char input_str[500]={0};char output_str[500]={0};char info[1000]={0};sprintf(input_str,"%s",(*env)->GetStringUTFChars(env,input_jstr, NULL));sprintf(output_str,"%s",(*env)->GetStringUTFChars(env,output_jstr, NULL));//FFmpeg av_log() callback av_log_set_callback(custom_log);av_register_all();avformat_network_init();pFormatCtx = avformat_alloc_context();if(avformat_open_input(&pFormatCtx,input_str,NULL,NULL)!=0){LOGE("Couldn’t open input stream.\n");return -1;}if(avformat_find_stream_info(pFormatCtx,NULL)<0){LOGE("Couldn’t find stream information.\n");return -1;}videoindex=-1;for(i=0; i<pFormatCtx->nb_streams; i++) if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){videoindex=i;break;}if(videoindex==-1){LOGE("Couldn’t find a video stream.\n");return -1;}pCodecCtx=pFormatCtx->streams[videoindex]->codec;pCodec=avcodec_find_decoder(pCodecCtx->codec_id);if(pCodec==NULL){LOGE("Couldn’t find Codec.\n");return -1;}if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){LOGE("Couldn’t open codec.\n");return -1;}pFrame=av_frame_alloc();pFrameYUV=av_frame_alloc();out_buffer=(uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);packet=(AVPacket *)av_malloc(sizeof(AVPacket));img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);sprintf(info, "[Input]%s\n", input_str); sprintf(info, "%s[Output ]%s\n",info,output_str); sprintf(info, "%s[Format ]%s\n",info, pFormatCtx->iformat->name); sprintf(info, "%s[Codec]%s\n",info, pCodecCtx->codec->name); sprintf(info, "%s[Resolution]%dx%d\n",info, pCodecCtx->width,pCodecCtx->height);fp_yuv=fopen(output_str,"wb+"); if(fp_yuv==NULL){printf("Cannot open output file.\n");return -1;}frame_cnt=0;time_start = clock();while(av_read_frame(pFormatCtx, packet)>=0){if(packet->stream_index==videoindex){ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);if(ret < 0){LOGE("Decode Error.\n");return -1;}if(got_picture){sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,pFrameYUV->data, pFrameYUV->linesize);y_size=pCodecCtx->width*pCodecCtx->height;fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Yfwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //Ufwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V//Output infochar pictype_str[10]={0};switch(pFrame->pict_type){case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;default:sprintf(pictype_str,"Other");break;}LOGI("Frame Index: %5d. Type:%s",frame_cnt,pictype_str);frame_cnt++;}}av_free_packet(packet);}//flush decoder//FIX: Flush Frames remained in Codecwhile (1) {ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);if (ret < 0)break;if (!got_picture)break;sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,pFrameYUV->data, pFrameYUV->linesize);int y_size=pCodecCtx->width*pCodecCtx->height;fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Y fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //Ufwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V//Output infochar pictype_str[10]={0};switch(pFrame->pict_type){case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break;case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break;case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break;default:sprintf(pictype_str,"Other");break;}LOGI("Frame Index: %5d. Type:%s",frame_cnt,pictype_str);frame_cnt++;}time_finish = clock(); time_duration=(double)(time_finish – time_start);sprintf(info, "%s[Time]%fms\n",info,time_duration);sprintf(info, "%s[Count]%d\n",info,frame_cnt);sws_freeContext(img_convert_ctx); fclose(fp_yuv);av_frame_free(&pFrameYUV);av_frame_free(&pFrame);avcodec_close(pCodecCtx);avformat_close_input(&pFormatCtx);return 0;}Android.mk文件位于jni/Android.mk，如下所示。# Android.mk for FFmpeg## Lei Xiaohua 雷霄骅# leixiaohua1020@126.com# # LOCAL_PATH := $(call my-dir)# FFmpeg libraryinclude $(CLEAR_VARS)LOCAL_MODULE := ffmpegLOCAL_SRC_FILES := libffmpeg.soinclude $(PREBUILT_SHARED_LIBRARY)# Programinclude $(CLEAR_VARS)LOCAL_MODULE := sffdecoderLOCAL_SRC_FILES :=simplest_ffmpeg_decoder.cLOCAL_C_INCLUDES += $(LOCAL_PATH)/includeLOCAL_LDLIBS := -llog -lzLOCAL_SHARED_LIBRARIES := ffmpeginclude $(BUILD_SHARED_LIBRARY)运行结果App在手机上运行后的结果如下图所示。
注意需要把等待解码的视频文件拷贝至存储卡相应的目录中。例如对于上述截图的情况，需要将sintel.mp4拷贝至存储卡的根目录中。
单击“Start”按钮就可以将存储卡根目录中的视频文件解码为YUV文件（需要等待一段时间完成解码）。注意解码后的YUV文件体积巨大，可能会占用大量的存储卡空间。
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simplest ffmpeg mobile项目主页
Github：https://github.com/leixiaohua1020/simplest_ffmpeg_mobile
开源中国：https://git.oschina.net/leixiaohua1020/simplest_ffmpeg_mobile
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