Android本地视频播放器开发--视频解码

在上一章Android本地视频播放器开发--SDL编译编译中编译出sdl的支持库，当时我们使用的2.0，但是有些api被更改了，所以在以下的使用者中我们使用SDL1.3的库，这个库我会传上源码以及编译出的库，接下来这张我们使用ffmpeg解码视频文件中的视频帧同时使用SDL去显示。

1、Decodec_Video.c 这是我视频解码的文件，其中内容如下:

#include <stdio.h>
#include <android/log.h>

#ifdef __MINGW32__
#undef main /* Prevents SDL from overriding main() */
#endif

#include "../SDL/include/SDL.h"
#include "../SDL/include/SDL_thread.h"

#include "VideoPlayerDecode.h"
#include "../ffmpeg/libavutil/avutil.h"
#include "../ffmpeg/libavcodec/avcodec.h"
#include "../ffmpeg/libavformat/avformat.h"
#include "../ffmpeg/libswscale/swscale.h"

AVFormatContext *pFormatCtx;
int             i, videoStream;
AVCodecContext  *pCodecCtx;
AVCodec         *pCodec;
AVFrame         *pFrame;
AVPacket        packet;
int             frameFinished;
float           aspect_ratio;

static struct SwsContext *img_convert_ctx;
SDL_Surface     *screen;
SDL_Overlay	*bmp;
SDL_Rect        rect;
SDL_Event       event;


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
	if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
		fprintf(stderr, "Could not initialize SDL - %s
", SDL_GetError());
		exit(1);
	}
	if(avformat_open_input(&pFormatCtx, local_title, NULL, NULL) != 0)
                return -1;
	if(avformat_find_stream_info(pFormatCtx, NULL) < 0)
                return -1;
	av_dump_format(pFormatCtx, -1, local_title, 0);
	videoStream=-1;
	for(i=0; i<pFormatCtx->nb_streams; i++)
		if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
			videoStream=i;
			break;
		}
	if(videoStream==-1)
		return -1; // Didn't find a video stream
	// Get a pointer to the codec context for the video stream
	pCodecCtx=pFormatCtx->streams[videoStream]->codec;

	// Find the decoder for the video stream
	pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
	if(pCodec==NULL) {
		fprintf(stderr, "Unsupported codec!
");
		return -1; // Codec not found
	}
	if(avcodec_open2(pCodecCtx, pCodec, NULL) < 0)return -1;
	pFrame = avcodec_alloc_frame();
	if(pFrame == NULL)return -1;
	// Make a screen to put our video
#ifndef __DARWIN__
	screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
#else
	screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 24, 0);
#endif
	if(!screen) {
		fprintf(stderr, "SDL: could not set video mode - exiting
");
		exit(1);
	}
	// Allocate a place to put our YUV image on that screen
	bmp = SDL_CreateYUVOverlay(pCodecCtx->width,
			pCodecCtx->height,
			SDL_YV12_OVERLAY,
			screen);
 	img_convert_ctx = sws_getContext(pCodecCtx->width,  
                          pCodecCtx->height, pCodecCtx->pix_fmt,  
                          pCodecCtx->width, pCodecCtx->height,  
                          PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);  

	// Read frames and save first five frames to disk
	i=0;
	while(av_read_frame(pFormatCtx, &packet)>=0) {
		// Is this a packet from the video stream?
		if(packet.stream_index==videoStream) {
			avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
			// Did we get a video frame?
			if(frameFinished) {
				SDL_LockYUVOverlay(bmp);
				
				AVPicture *pict;
				pict->data[0] = bmp->pixels[0];
				pict->data[1] = bmp->pixels[2];
				pict->data[2] = bmp->pixels[1];

				pict->linesize[0] = bmp->pitches[0];
				pict->linesize[1] = bmp->pitches[2];
				pict->linesize[2] = bmp->pitches[1];
				
sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pict->data, pict->linesize);
				SDL_UnlockYUVOverlay(bmp);

				rect.x = 0;
				rect.y = 0;
				rect.w = pCodecCtx->width;
				rect.h = pCodecCtx->height;
				SDL_DisplayYUVOverlay(bmp, &rect);

			}
		}
		// Free the packet that was allocated by av_read_frame
		av_free_packet(&packet);
		SDL_PollEvent(&event);
		switch(event.type) {
			case SDL_QUIT:
				SDL_Quit();
				exit(0);
				break;
			default:
				break;
		}

	}
	// Free the YUV frame
	av_free(pFrame);

	// Close the codec
	avcodec_close(pCodecCtx);

	// Close the video file
	av_close_input_file(pFormatCtx);
}

2、编译结果如下:

root@zhangjie:/Graduation/jni# ndk-build
Install        : libSDL.so => libs/armeabi/libSDL.so
Install        : libffmpeg-neon.so => libs/armeabi/libffmpeg-neon.so
Compile arm    : ffmpeg-test-neon <= Decodec_Video.c
/Graduation/jni/jniffmpeg/Decodec_Video.c: In function 'Java_com_zhangjie_graduation_videopalyer_jni_VideoPlayerDecode_VideoPlayer':
/Graduation/jni/jniffmpeg/Decodec_Video.c:106:1: warning: passing argument 2 of 'sws_scale' from incompatible pointer type [enabled by default]
/Graduation/jni/jniffmpeg/../ffmpeg/libswscale/swscale.h:237:5: note: expected 'uint8_t const * const*' but argument is of type 'uint8_t **'
/Graduation/jni/jniffmpeg/Decodec_Video.c:137:2: warning: 'av_close_input_file' is deprecated (declared at /Graduation/jni/jniffmpeg/../ffmpeg/libavformat/avformat.h:1533) [-Wdeprecated-declarations]
SharedLibrary  : libffmpeg-test-neon.so
Install        : libffmpeg-test-neon.so => libs/armeabi/libffmpeg-test-neon.so

3、SDL1.3源码

http://download.csdn.net/detail/jwzhangjie/5596453

4、之前在Android本地视频播放器开发--NDK编译FFmpeg中没有添加swscale功能，所以需要重新编译ffmpeg，其脚本如下:

NDK=/opt/android-ndk-r8d
PLATFORM=$NDK/platforms/android-8/arch-arm/
PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
LOCAL_ARM_NEON=true
CPU=armv7-a
OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=neon -marm -mcpu=cortex-a8"
PREFIX=./android/$CPU
./configure --target-os=linux 
    --prefix=$PREFIX 
    --enable-cross-compile 
    --arch=arm 
    --enable-nonfree 
    --enable-asm 
    --cpu=cortex-a8 
    --enable-neon 
    --cc=$PREBUILT/bin/arm-linux-androideabi-gcc 
    --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- 
    --nm=$PREBUILT/bin/arm-linux-androideabi-nm 
    --sysroot=$PLATFORM 
    --extra-cflags=" -O3 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 $OPTIMIZE_CFLAGS " 
    --disable-shared 
    --enable-static 
    --extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -nostdlib -lc -lm -ldl -llog" 
    --disable-ffmpeg 
    --disable-ffplay 
    --disable-ffprobe 
    --disable-ffserver 
    --disable-encoders 
    --enable-avformat 
    --disable-optimizations 
    --disable-doc 
    --enable-pthreads 
    --disable-yasm 
    --enable-zlib 
    --enable-pic 
    --enable-small

#make clean
make  -j4 install

$PREBUILT/bin/arm-linux-androideabi-ar d libavcodec/libavcodec.a inverse.o

$PREBUILT/bin/arm-linux-androideabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -soname libffmpeg-neon.so -shared -nostdlib  -z noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg-neon.so libavcodec/libavcodec.a libavformat/libavformat.a libavutil/libavutil.a  libavfilter/libavfilter.a libswresample/libswresample.a libswscale/libswscale.a libavdevice/libavdevice.a -lc -lm -lz -ldl -llog  --warn-once  --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-linux-androideabi/4.4.3/libgcc.a