正点原子linux开发板使用ffmpeg代码播放视频

先说下原因，我想用开发板拉取摄像头的网络流，然后显示出来。
共分为两步，
第一步：本地使用ffmpeg播放视频。
第二部：ffmpeg拉取摄像头的数据，播放视频。
现在第一步实现了，视频见B站。
代码实现播放视频的效果

代码我会上传百度网盘，包括了ffmpeg_V3.4.6的库文件，代码，Makefile
链接：https://pan.baidu.com/s/1MGMeW0yAbKGjiv5XMVguqg
提取码：p8qv

后来我发现代码存在内存泄漏的问题，所以后面我修改了，详见下篇文章
拉流RTSP并播放

我说下实现的步骤

step1 使用buildroot构建rootfs

按照原子的教程，使用buildroot-2019.02.6.tar.bz2构建一个基本的rootfs，然后在target_packet 增加ffmpeg和其他软件的编译。

step2 生成ffmepg的库和头文件

我们的目标是ffmpeg代码实现视频解码，所以需要ffmpeg的库和头文件。
但是buildroot自行编译完ffmepg后，我不知道ffmpeg的库和头文件放哪了。
所以我只是让buildroot下载ffmepg代码，然后需要我手动指定编译的条件。ffmpeg的编译过程参考我之前的文章。
ubuntu16.04搭建ffmepg开发环境

由于这里是嵌入式环境，ffmpeg的config命令的参数肯定不能完全照搬PC端的内容，所以我把buildroot编译出来的ffmpeg的参数稍微一改即可。
怎么获取呢，直接在开发板运行ffmpeg，就会打印ffmpeg编译时的配置参数。是否很神奇，哈哈。

这些参数都是类似的，只需要看懂unbuntu下如何编译ffmpeg，这些参数很容易看懂，我修改的参数有这些，–prefix，

--prefix：编译出的库文件和头文件存放的路径，在make install使用
--enable-ffplay：使能ffplay的编译，最后就会编译出ffplay可执行文件
--enable-postproc 
--enable-swscale：程序使用到了这两个库，所以要使能编译。

所以修改完以后的ffmpeg配置命令如下：

sudo ./configure \
--prefix="$HOME/alpha_build" \
--pkg-config-flags="--static" \
--extra-cflags="-I$HOME/alpha_build/include" \
--extra-ldflags="-L$HOME/alpha_build/lib" \
--enable-cross-compile \
--cross-prefix=/home/shengy/tool/buildroot-2019.02.6/output/host/bin/arm-linux-gnueabihf- \
--sysroot=/home/shengy/tool/buildroot-2019.02.6/output/host/arm-buildroot-linux-gnueabihf/sysroot \
--host-cc=/usr/bin/gcc --arch=arm --target-os=linux --disable-stripping \
--pkg-config=/home/shengy/tool/buildroot-2019.02.6/output/host/bin/pkg-config \
--disable-static --enable-shared --enable-avfilter --disable-version3 \
--enable-logging --enable-optimizations --disable-extra-warnings --enable-avdevice \
--enable-avcodec --enable-avformat --enable-network --disable-gray --enable-swscale-alpha \
--disable-small --enable-dct --enable-fft --enable-mdct --enable-rdft --disable-crystalhd \
--disable-dxva2 --enable-runtime-cpudetect --disable-hardcoded-tables --disable-mipsdsp \
--disable-mipsdspr2 --disable-msa --enable-hwaccels --disable-cuda --disable-cuvid \
--disable-nvenc --disable-avisynth --disable-frei0r --disable-libopencore-amrnb \
--disable-libopencore-amrwb --disable-libdc1394 --disable-libgsm --disable-libilbc \
--disable-libvo-amrwbenc --disable-symver --disable-doc --disable-gpl --disable-nonfree \
--enable-ffmpeg --enable-ffplay --disable-ffserver --disable-avresample --enable-ffprobe \
--enable-postproc --enable-swscale --enable-indevs --disable-alsa --enable-outdevs \
--enable-pthreads --disable-zlib --disable-bzlib --disable-libfdk-aac --disable-libcdio \
--disable-gnutls --disable-openssl --disable-libdrm --disable-libopenh264 --disable-vaapi \
--disable-vdpau --disable-mmal --disable-omx --disable-omx-rpi --disable-libopencv \
--disable-libopus --disable-libvpx --disable-libass --disable-libbluray --disable-librtmp --disable-libmp3lame \
--disable-libmodplug --disable-libspeex --disable-libtheora --disable-libwavpack --disable-iconv \
--disable-libfreetype --disable-fontconfig --disable-libopenjpeg --disable-libx264 --disable-libx265 \
--disable-x86asm --disable-mmx --disable-sse --disable-sse2 --disable-sse3 --disable-ssse3 --disable-sse4 \
--disable-sse42 --disable-avx --disable-avx2 --enable-armv6 --enable-vfp --enable-neon --disable-altivec \
--extra-libs=-latomic --enable-pic --cpu=cortex-a7

执行完这个命令，就是编译ffmpeg了，

sudo make -j16
make install       #make install后，ffmpeg的库和头文件就放到了--prefix指定的路径

step3 代码开发

这个就参考网上的例程，各种拼接。我这里ffmpeg的版本就是buildroot下载下来的V3.4.6.
主要步骤是解码，和转换。因为解码后的data数据是YUV420P，而且视频分辨率和屏幕不匹配，所以需要转换。 最好是视频分辨率就是屏幕尺寸，这样问题会少一些。

新建test_002_copy.c文件，代码如下：

/*
 * Copyright (c) 2015 Ludmila Glinskih
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
/**
 * H264 codec test.
 */
#include 
#include 
#include 
#include 
#include 
#include 

#include "libavutil/adler32.h"
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libavutil/imgutils.h"

#include "libavfilter/avfilter.h"
#include "libavutil/avutil.h"
#include "libavutil/pixfmt.h"
#include "libavdevice/avdevice.h"
#include "libswscale/swscale.h"
#include "libswresample/swresample.h"


typedef unsigned char  uint8_t;

int fbfd = 0;
static unsigned int* fbp = NULL;
struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
int scrWid = 0;
int scrHeg = 0;

int open_fb()
{
    unsigned int screen_size;
   /* 打开framebuffer设备 */
    if (0 > (fbfd = open("/dev/fb0", O_RDWR))) {
        perror("open error");
        exit(EXIT_FAILURE);
    }

    /* 获取参数信息 */
    ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo);
    ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo);

    screen_size = finfo.line_length * vinfo.yres;
    scrWid = vinfo.xres;
    scrHeg = vinfo.yres;

    /* 将显示缓冲区映射到进程地址空间 */
    fbp = mmap(NULL, screen_size, PROT_WRITE, MAP_SHARED, fbfd, 0);
    if (MAP_FAILED == (void *)fbp) {
        perror("mmap error");
        close(fbfd);
        exit(EXIT_FAILURE);
    }

    scrWid = vinfo.xres;
    scrHeg = vinfo.yres;
    printf("scrWid:%d scrHeg:%d\n", scrWid, scrHeg );
}

void close_fb(void)
{
    // 解除映射并关闭framebuffer设备
    munmap(fbp, finfo.smem_len);
    close(fbfd);
}

#define argb8888_to_rgba888(color)   ({ \
            unsigned int temp = (color); \
            ((temp & 0xff0000UL) >> 16) | \
            ((temp & 0xff00UL) >> 0) | \
            ((temp & 0xffUL) << 16); \
            })

/********************************************************************
 * 函数名称： lcd_draw_point
 * 功能描述： 打点
 * 输入参数： x, y, color
 * 返 回 值： 无
 ********************************************************************/
static void lcd_draw_point(unsigned int x, unsigned int y, unsigned int color)
{
    unsigned int rgb565_color = argb8888_to_rgba888(color);//得到RGB565颜色值

   
    /* 填充颜色 */
    fbp[y * scrWid + x] = color;
}

void draw_point(int x, int y, uint8_t *color)
{
    lcd_draw_point(x, y, *(uint32_t *)color);
}

void clr_scr(int w, int h)
{
    static int cnt = 0;
    printf("clr scr:%d\n", cnt);
    cnt++;

    char clor[4] = {0xff, 0xff, 0xff};

    for(int i = 0; i < h; i++)
        for(int j = 0; j < w; j++)
            draw_point(j, i, clor);
    
}

int32_t VideoConvert(
    const AVFrame *pInFrame,  // 输入视频帧
    enum AVPixelFormat eOutFormat, // 输出视频格式
    int32_t nOutWidth,        // 输出视频宽度
    int32_t nOutHeight,       // 输出视频高度
    AVFrame **ppOutFrame)     // 输出视频帧
{
    struct SwsContext *pSwsCtx ;
    AVFrame *pOutFrame = NULL;

    // 创建格式转换器, 指定缩放算法,转换过程中不增加任何滤镜特效处理
    pSwsCtx = sws_getContext(pInFrame->width, pInFrame->height, (enum AVPixelFormat)pInFrame->format,
                             nOutWidth, nOutHeight, eOutFormat,
                             SWS_BICUBIC, NULL, NULL, NULL);
    if (pSwsCtx == NULL)
    {
        printf(" [ERROR] fail to sws_getContext()\n");
        return -1;
    }

    // 创建输出视频帧对象以及分配相应的缓冲区
    uint8_t *data[4] = {NULL};
    int linesize[4] = {0};
    int res = av_image_alloc(data, linesize, nOutWidth, nOutHeight, eOutFormat, 1);
    if (res < 0)
    {
        printf(" [ERROR] fail to av_image_alloc(), res=%d\n", res);
        sws_freeContext(pSwsCtx);
        return -2;
    }
    pOutFrame = av_frame_alloc();
    pOutFrame->format = eOutFormat;
    pOutFrame->width = nOutWidth;
    pOutFrame->height = nOutHeight;
    pOutFrame->data[0] = data[0];
    pOutFrame->data[1] = data[1];
    pOutFrame->data[2] = data[2];
    pOutFrame->data[3] = data[3];
    pOutFrame->linesize[0] = linesize[0];
    pOutFrame->linesize[1] = linesize[1];
    pOutFrame->linesize[2] = linesize[2];
    pOutFrame->linesize[3] = linesize[3];

    // 进行格式转换处理
    res = sws_scale(pSwsCtx,
                    (const uint8_t *const *)(pInFrame->data),
                    pInFrame->linesize,
                    0,
                    pOutFrame->height,
                    pOutFrame->data,
                    pOutFrame->linesize);
    if (res < 0)
    {
        printf(" [ERROR] fail to sws_scale(), res=%d\n", res);
        sws_freeContext(pSwsCtx);
        av_frame_free(&pOutFrame);
        return -3;
    }

    (*ppOutFrame) = pOutFrame;
    sws_freeContext(pSwsCtx); // 释放转换器
    return 0;
}


static int video_decode_example(const char *input_filename)
{
    AVCodec *codec = NULL;
    AVCodecContext *ctx= NULL;
    AVCodecParameters *origin_par = NULL;
    AVFrame *fr = NULL;
    AVFrame *outfrarme = NULL;
    uint8_t *byte_buffer = NULL;
    AVPacket pkt;
    AVFormatContext *fmt_ctx = NULL;
    int number_of_written_bytes;
    int video_stream;
    int got_frame = 0;
    int byte_buffer_size;
    int i = 0;
    int result;
    int end_of_stream = 0;
 
    result = avformat_open_input(&fmt_ctx, input_filename, NULL, NULL);
    if (result < 0) {
        av_log(NULL, AV_LOG_ERROR, "Can't open file, res:%d\n", result);
        return result;
    }
 
    result = avformat_find_stream_info(fmt_ctx, NULL);
    if (result < 0) {
        av_log(NULL, AV_LOG_ERROR, "Can't get stream info\n");
        return result;
    }
 
    video_stream = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
    if (video_stream < 0) {
      av_log(NULL, AV_LOG_ERROR, "Can't find video stream in input file\n");
      return -1;
    }
 
    origin_par = fmt_ctx->streams[video_stream]->codecpar;
 
    codec = avcodec_find_decoder(origin_par->codec_id);
    if (!codec) {
        av_log(NULL, AV_LOG_ERROR, "Can't find decoder\n");
        return -1;
    }
 
    ctx = avcodec_alloc_context3(codec);
    if (!ctx) {
        av_log(NULL, AV_LOG_ERROR, "Can't allocate decoder context\n");
        return AVERROR(ENOMEM);
    }
 
    result = avcodec_parameters_to_context(ctx, origin_par);
    if (result) {
        av_log(NULL, AV_LOG_ERROR, "Can't copy decoder context\n");
        return result;
    }
 
    result = avcodec_open2(ctx, codec, NULL);
    if (result < 0) {
        av_log(ctx, AV_LOG_ERROR, "Can't open decoder\n");
        return result;
    }
 
    fr = av_frame_alloc();
    if (!fr) {
        av_log(NULL, AV_LOG_ERROR, "Can't allocate frame\n");
        return AVERROR(ENOMEM);
    }
 
    printf("#tb %d: %d/%d\n", video_stream, fmt_ctx->streams[video_stream]->time_base.num, 
                                fmt_ctx->streams[video_stream]->time_base.den);
    i = 0;
    av_init_packet(&pkt);
    do {
        if (!end_of_stream)
            if (av_read_frame(fmt_ctx, &pkt) < 0)
                end_of_stream = 1;
        if (end_of_stream) {
            pkt.data = NULL;
            pkt.size = 0;
        }
        if (pkt.stream_index == video_stream || end_of_stream) {
            got_frame = 0;
            if (pkt.pts == AV_NOPTS_VALUE)
                pkt.pts = pkt.dts = i;
            result = avcodec_decode_video2(ctx, fr, &got_frame, &pkt);
            if (result < 0) {
                av_log(NULL, AV_LOG_ERROR, "Error decoding frame\n");
                return result;
            }
            if (got_frame) {
                    int out_w = 800;
                    int out_h = 480;
                    
                    VideoConvert(fr, AV_PIX_FMT_BGRA, out_w, out_h, &outfrarme);
           

                    for(int h = 0; h < out_h; h++)
                        for(int w = 0; w < out_w; w++)
                        {
                            draw_point(w, h, (outfrarme->data[0])+ ((h * out_w *4 + w * 4)));
                        }
                    printf("draw one pic\n");
                    
                }
            av_frame_free(&outfrarme);
            av_packet_unref(&pkt);
            av_init_packet(&pkt);
        }
        i++;
    } while (!end_of_stream || got_frame);
 
    av_packet_unref(&pkt);
    av_frame_free(&fr);
    avcodec_close(ctx);
    avformat_close_input(&fmt_ctx);
    avcodec_free_context(&ctx);
    av_freep(&byte_buffer);
    return 0;
}
 
int main(int argc, char **argv)
{
    if (argc < 2)
    {
        av_log(NULL, AV_LOG_ERROR, "Incorrect input\n");
        return 1;
    }
    avcodec_register_all();
#if CONFIG_AVDEVICE
    avdevice_register_all();
#endif

   avfilter_register_all();

    av_register_all();
    open_fb();
    clr_scr(scrWid, scrHeg);
    usleep(1000 * 1000 * 1);

    if (video_decode_example(argv[1]) != 0)
        return 1;
    
    close_fb();
    return 0;
}

makefile文件内容如下：

FFMPEG=/home/shengy/alpha_build/
CC=arm-linux-gnueabihf-gcc

CFLAGS=-g -I$(FFMPEG)/include

LDFLAGS = -L$(FFMPEG)/lib/  -lswresample -lavformat -lavdevice -lavcodec -lavutil -lswscale -lavfilter -lm
TARGETS=test_002_copy

all:$(TARGETS)
	
test_002_copy:test_002_copy.c
	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS) -std=c99  
	
clean:
	rm -rf $(TARGETS)

编译后，执行./test_002_copy 视频文件.mp4
然后就可以播放视频了。