FFmpeg YUV视频序列编码为视频

上一篇已经写了如何配置好开发环境，这次就先小试牛刀，来个视频的编码。搞视频处理的朋友肯定比较熟悉YUV视频序列，很多测试库提供的视频数据都是YUV视频序列，我们这里就用用YUV视频序列来做视频。关于YUV视频序列，我就不多讲了，可以看书学习，通常的视频序列都是YUV420格式的。

步骤也就那几步，添加视频流，打开编码器，开辟相应的内存空间，然后就可以打开YUV序列逐帧写入数据了，so easy！记得最后要做好文件的关闭和内存的释放，因为FFmpeg是c风格的（不知道新版本是否是c++风格的），这些工作都需要自己做好啊。过多的说明是没用的，直接上代码：

这里我补充一下，大多数的视频格式好像只支持YUV格式的视频帧AVFrame，我试图直接把RGB的视频序列直接编码到视频这条路好像走不通，都需要把RGB的视频帧再转成YUV视频帧才行，不知道高手有没有其他高见。

#include <stdio.h>
#include <string.h>

extern "C"
{
#include <libavcodec\avcodec.h>
#include <libavformat\avformat.h>
#include <libswscale\swscale.h>
};

void main(int argc, char ** argv)
{
AVFormatContext* oc;
AVOutputFormat* fmt;
AVStream* video_st;
double video_pts;
uint8_t* video_outbuf;
uint8_t* picture_buf;
AVFrame* picture;
//     AVFrame* pictureRGB;
int size;
int ret;
int video_outbuf_size;

FILE *fin = fopen("akiyo_qcif.yuv", "rb"); //视频源文件

const char* filename = "test.mpg";
//     const char* filename;
//     filename = argv[1];

av_register_all();

//     avcodec_init(); // 初始化codec库
//     avcodec_register_all(); // 注册编码器

fmt = guess_format(NULL, filename, NULL);
oc = av_alloc_format_context();
oc->oformat = fmt;
snprintf(oc->filename, sizeof(oc->filename), "%s", filename);

video_st = NULL;
if (fmt->video_codec != CODEC_ID_NONE)
{
AVCodecContext* c;
video_st = av_new_stream(oc, 0);
c = video_st->codec;
c->codec_id = fmt->video_codec;
c->codec_type = CODEC_TYPE_VIDEO;
c->bit_rate = 400000;
c->width = 176;
c->height = 144;
c->time_base.num = 1;
c->time_base.den = 25;
c->gop_size = 12;
c->pix_fmt = PIX_FMT_YUV420P;
if (c->codec_id == CODEC_ID_MPEG2VIDEO)
{
c->max_b_frames = 2;
}
if (c->codec_id == CODEC_ID_MPEG1VIDEO)
{
c->mb_decision = 2;
}
if (!strcmp(oc->oformat->name, "mp4") || !strcmp(oc->oformat->name, "mov") || !strcmp(oc->oformat->name, "3gp"))
{
c->flags |= CODEC_FLAG_GLOBAL_HEADER;
}
}

if (av_set_parameters(oc, NULL)<0)
{
return;
}

dump_format(oc, 0, filename, 1);
if (video_st)
{
AVCodecContext* c;
AVCodec* codec;
c = video_st->codec;
codec = avcodec_find_encoder(c->codec_id);
if (!codec)
{
return;
}
if (avcodec_open(c, codec) < 0)
{
return;
}
if (!(oc->oformat->flags & AVFMT_RAWPICTURE))
{
video_outbuf_size = 200000;
video_outbuf = (uint8_t*)av_malloc(video_outbuf_size);
}
picture = avcodec_alloc_frame();
size = avpicture_get_size(c->pix_fmt, c->width, c->height);
picture_buf = (uint8_t*)av_malloc(size);
if (!picture_buf)
{
av_free(picture);
}
avpicture_fill((AVPicture*)picture, picture_buf, c->pix_fmt, c->width, c->height);
}

if (!(fmt->flags & AVFMT_NOFILE))
{
if (url_fopen(&oc->pb, filename, URL_WRONLY) < 0)
{
return;
}
}
av_write_header(oc);

for (int i=0; i<300; i++)
{
if (video_st)
{
video_pts = (double)(video_st->pts.val * video_st->time_base.num / video_st->time_base.den);
}
else
{
video_pts = 0.0;
}
if (!video_st/* || video_pts >= 5.0*/)
{
break;
}
AVCodecContext* c;
c = video_st->codec;
size = c->width * c->height;

if (fread(picture_buf, 1, size*3/2, fin) < 0)
{
break;
}

picture->data[0] = picture_buf;  // 亮度
picture->data[1] = picture_buf+ size;  // 色度
picture->data[2] = picture_buf+ size*5/4; // 色度

// 如果是rgb序列，可能需要如下代码
//         SwsContext* img_convert_ctx;
//         img_convert_ctx = sws_getContext(c->width, c->height, PIX_FMT_RGB24, c->width, c->height, c->pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);
//         sws_scale(img_convert_ctx, pictureRGB->data, pictureRGB->linesize, 0, c->height, picture->data, picture->linesize);

if (oc->oformat->flags & AVFMT_RAWPICTURE)
{
AVPacket pkt;
av_init_packet(&pkt);
pkt.flags |= PKT_FLAG_KEY;
pkt.stream_index = video_st->index;
pkt.data = (uint8_t*)picture;
pkt.size = sizeof(AVPicture);
ret = av_write_frame(oc, &pkt);
}
else
{
int out_size = avcodec_encode_video(c, video_outbuf, video_outbuf_size, picture);
if (out_size > 0)
{
AVPacket pkt;
av_init_packet(&pkt);
pkt.pts = av_rescale_q(c->coded_frame->pts, c->time_base, video_st->time_base);
if (c->coded_frame->key_frame)
{
pkt.flags |= PKT_FLAG_KEY;
}
pkt.stream_index = video_st->index;
pkt.data = video_outbuf;
pkt.size = out_size;
ret = av_write_frame(oc, &pkt);
}
}
}

if (video_st)
{
avcodec_close(video_st->codec);
//         av_free(picture->data[0]);
av_free(picture);
av_free(video_outbuf);
//         av_free(picture_buf);
}
av_write_trailer(oc);
for (int i=0; i<oc->nb_streams; i++)
{
av_freep(&oc->streams[i]->codec);
av_freep(&oc->streams[i]);
}
if (!(fmt->flags & AVFMT_NOFILE))
{
url_fclose(oc->pb);
}
av_free(oc);
}

上一篇介绍了视频编码的小例子，视频解码跟编码差不多，只是要在视频文件中寻找视频流，找到后对流逐帧解码，就这样简单。闲言少叙，上code：

int main(int argc, char *argv[])
{
AVFormatContext *pFormatCtx;
int             i, videoStream;
AVCodecContext  *pCodecCtx;
AVCodec         *pCodec;
AVFrame         *pFrame;
AVFrame         *pFrameRGB;
AVPacket        packet;
int             frameFinished;
int             numBytes;
uint8_t         *buffer;
struct SwsContext *img_convert_ctx;

if(argc < 2)
{
printf("Please provide a movie file\n");
return -1;
}
// Register all formats and codecs
// 初始化ffmpeg库
av_register_all();

// Open video file
if(av_open_input_file(&pFormatCtx, argv[1], NULL, 0, NULL)!=0)
return -1; // Couldn't open file

// Retrieve stream information
// 查找文件的流信息
if(av_find_stream_info(pFormatCtx)<0)
return -1; // Couldn't find stream information

// Dump information about file onto standard error
// dump只是一个调试函数，输出文件的音、视频流的基本信息：帧率、分辨率、音频采样等等
dump_format(pFormatCtx, 0, argv[1], 0);

// Find the first video stream
// 遍历文件的流，找到第一个视频流，并记录流的编码信息
videoStream=-1;
for(i=0; i<pFormatCtx->nb_streams; i++)
{
if(pFormatCtx->streams[i]->codec->codec_type==CODEC_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
// 得到视频流编码的上下文指针
pCodecCtx=pFormatCtx->streams[videoStream]->codec;

// construct the scale context, conversing to PIX_FMT_RGB24
// 根据编码信息设置渲染格式
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height, PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);
if(img_convert_ctx == NULL)
{
fprintf(stderr, "Cannot initialize the conversion context!\n");
//         exit(1);
return -1;
}

// Find the decoder for the video stream
// 在库里面查找支持该格式的解码器
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL)
{
fprintf(stderr, "Unsupported codec!\n");
return -1; // Codec not found
}
// Open codec
// 打开解码器
if(avcodec_open(pCodecCtx, pCodec)<0)
return -1; // Could not open codec

// Allocate video frame
// 分配一个帧指针，指向解码后的原始帧
pFrame=avcodec_alloc_frame();

// Allocate an AVFrame structure
// 分配一个帧指针，指向存放转换成rgb后的帧
pFrameRGB=avcodec_alloc_frame();
if(pFrameRGB==NULL)
return -1;

// Determine required buffer size and allocate buffer
numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height);
buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));    // buffer = new uint8_t[numBytes];

// Assign appropriate parts of buffer to image planes in pFrameRGB
// Note that pFrameRGB is an AVFrame, but AVFrame is a superset
// of AVPicture
// 给pFrameRGB帧附加上分配的内存
avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height);

// Read frames and save first five frames to disk
i=0;
while(av_read_frame(pFormatCtx, &packet)>=0)    // 读取一个帧
{
// Is this a packet from the video stream?
if(packet.stream_index==videoStream)
{
// Decode video frame
// 解码该帧
avcodec_decode_video(pCodecCtx, pFrame, &frameFinished, packet.data, packet.size);

// Did we get a video frame?
if(frameFinished)
{
// Convert the image from its native format to RGB
// img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24,
//                 (AVPicture*)pFrame, pCodecCtx->pix_fmt, pCodecCtx->width,
//              pCodecCtx->height);

// 把该帧转换成rgb

// 如果只提取关键帧，加上这句
// if (pFrame->key_frame == 1)
sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
// Save the frame to disk
// 保存前5帧
if(++i<=5)
{
//                     char pic[200];
//                     sprintf(pic,"pic%d.bmp",i);
//                     av_create_bmp(pic, pFrameRGB->data[0], pCodecCtx->width, pCodecCtx->height, 24);
SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i);
}
}
}

// Free the packet that was allocated by av_read_frame
// 释放读取的帧内存
av_free_packet(&packet);
}

// Free the RGB image
av_free(buffer);
av_free(pFrameRGB);

// Free the YUV frame
av_free(pFrame);

// Close the codec
avcodec_close(pCodecCtx);

// Close the video file
av_close_input_file(pFormatCtx);

return 0;
}

FFmpeg浅尝辄止（四）——音频的解码和编码

音频和视频其实是一样的，在文件中寻找音频流，然后解压出来，得到音频帧的数据，同样也可以按照设定的编码格式进行压缩，我这里把音频的解码和编码做成了两个工程，也是直接上代码：

#include <stdio.h>
#include <stdlib.h>

extern "C"
{
#include <libavcodec\avcodec.h>
#include <libavformat\avformat.h>
#include <libswscale\swscale.h>
}

int main(char arg,char *argv[])
{
char *filename = argv[1];

av_register_all();    //注册所有可解码类型
AVFormatContext *pInFmtCtx=NULL;    //文件格式
AVCodecContext *pInCodecCtx=NULL;    //编码格式
if (av_open_input_file(&pInFmtCtx, filename, NULL, 0, NULL)!=0)    //获取文件格式
printf("av_open_input_file error\n");
if (av_find_stream_info(pInFmtCtx) < 0)    //获取文件内音视频流的信息
printf("av_find_stream_info error\n");

unsigned int j;
// Find the first audio stream

int audioStream = -1;
for (j=0; j<pInFmtCtx->nb_streams; j++)    //找到音频对应的stream
{
if (pInFmtCtx->streams[j]->codec->codec_type == CODEC_TYPE_AUDIO)
{
audioStream = j;
break;
}
}
if (audioStream == -1)
{
printf("input file has no audio stream\n");
return 0; // Didn't find a audio stream
}
printf("audio stream num: %d\n",audioStream);
pInCodecCtx = pInFmtCtx->streams[audioStream]->codec; //音频的编码上下文
AVCodec *pInCodec = NULL;

pInCodec = avcodec_find_decoder(pInCodecCtx->codec_id); //根据编码ID找到用于解码的结构体
if (pInCodec == NULL)
{
printf("error no Codec found\n");
return -1 ; // Codec not found
}

if(avcodec_open(pInCodecCtx, pInCodec)<0)//将两者结合以便在下面的解码函数中调用pInCodec中的对应解码函数
{
printf("error avcodec_open failed.\n");
return -1; // Could not open codec

}

static AVPacket packet;

printf(" bit_rate = %d \r\n", pInCodecCtx->bit_rate);
printf(" sample_rate = %d \r\n", pInCodecCtx->sample_rate);
printf(" channels = %d \r\n", pInCodecCtx->channels);
printf(" code_name = %s \r\n", pInCodecCtx->codec->name);
printf(" block_align = %d\n",pInCodecCtx->block_align);

uint8_t *pktdata;
int pktsize;
int out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE*100;
uint8_t * inbuf = (uint8_t *)malloc(out_size);
FILE* pcm;
pcm = fopen("result.pcm","wb");
long start = clock();
while (av_read_frame(pInFmtCtx, &packet) >= 0)//pInFmtCtx中调用对应格式的packet获取函数
{
if(packet.stream_index==audioStream)//如果是音频
{
pktdata = packet.data;
pktsize = packet.size;
while(pktsize>0)
{
out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE*100;
//解码
int len = avcodec_decode_audio2(pInCodecCtx, (short*)inbuf, &out_size, pktdata, pktsize);
if (len < 0)
{
printf("Error while decoding.\n");
break;
}
if(out_size > 0)
{
fwrite(inbuf,1,out_size,pcm);//pcm记录
fflush(pcm);
}
pktsize -= len;
pktdata += len;
}
}
av_free_packet(&packet);
}
long end = clock();
printf("cost time :%f\n",double(end-start)/(double)CLOCKS_PER_SEC);
free(inbuf);
fclose(pcm);
if (pInCodecCtx!=NULL)
{
avcodec_close(pInCodecCtx);
}
av_close_input_file(pInFmtCtx);

return 0;
}

解码后的文件保存为result.pcm中，现在用这个文件压缩出新的音频文件，代码如下：

void main()
{
int16_t *samples;
uint8_t *audio_outbuf;
int audio_outbuf_size;
int audio_input_frame_size;
double audio_pts;

const char* filename = "test.wav";
FILE *fin = fopen("result.pcm", "rb"); //音频源文件
AVOutputFormat *fmt;
AVFormatContext *oc;
AVStream * audio_st;
av_register_all();
fmt = guess_format(NULL, filename, NULL);
oc = av_alloc_format_context();
oc->oformat = fmt;
snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
audio_st = NULL;

if (fmt->audio_codec != CODEC_ID_NONE)
{
AVCodecContext *c;
audio_st = av_new_stream(oc, 1);
c = audio_st->codec;
c->codec_id = fmt->audio_codec;
c->codec_type = CODEC_TYPE_AUDIO;
c->bit_rate = 128000;
c->sample_rate = 44100;
c->channels = 2;
}
if (av_set_parameters(oc, NULL) < 0)
{
return;
}
dump_format(oc, 0, filename, 1);
if (audio_st)
{
AVCodecContext* c;
AVCodec* codec;
c = audio_st->codec;
codec = avcodec_find_encoder(c->codec_id);
avcodec_open(c, codec);
audio_outbuf_size = 10000;
audio_outbuf = (uint8_t*)av_malloc(audio_outbuf_size);
if (c->frame_size <= 1)
{
audio_input_frame_size = audio_outbuf_size / c->channels;
switch (audio_st->codec->codec_id)
{
case CODEC_ID_PCM_S16LE:
case CODEC_ID_PCM_S16BE:
case CODEC_ID_PCM_U16LE:
case CODEC_ID_PCM_U16BE:
audio_input_frame_size >>= 1;
break;
default:
break;
}
}
else
{
audio_input_frame_size = c->frame_size;
}
samples = (int16_t*)av_malloc(audio_input_frame_size*2*c->channels);
}
if (!fmt->flags & AVFMT_NOFILE)
{
if (url_fopen(&oc->pb, filename, URL_WRONLY) < 0)
{
return;
}
}
av_write_header(oc);
for (;;)
{
if (audio_st)
{
audio_pts = (double)audio_st->pts.val * audio_st->time_base.num / audio_st->time_base.den;
}
else
{
audio_pts = 0.0;
}
if (!audio_st || audio_pts >= 360.0)
{
break;
}
if (fread(samples, 1, audio_input_frame_size*2*audio_st->codec->channels, fin) <= 0)
{
break;
}
AVCodecContext* c;
AVPacket pkt;
av_init_packet(&pkt);
c = audio_st->codec;
pkt.size = avcodec_encode_audio(c, audio_outbuf, audio_outbuf_size, samples);
pkt.pts = av_rescale_q(c->coded_frame->pts, c->time_base, audio_st->time_base);
pkt.flags |= PKT_FLAG_KEY;
pkt.stream_index = audio_st->index;
pkt.data = audio_outbuf;
if (av_write_frame(oc, &pkt) != 0)
{
return;
}
}
if (audio_st)
{
avcodec_close(audio_st->codec);
av_free(samples);
av_free(audio_outbuf);
}
av_write_trailer(oc);
for (int i=0; i<oc->nb_streams; i++)
{
av_freep(&oc->streams[i]->codec);
av_freep(&oc->streams[i]);
}
if (!(fmt->flags & AVFMT_NOFILE))
{
url_fclose(oc->pb);
}
av_free(oc);
fclose(fin);
}

对应的下载链接：
http://download.csdn.net/detail/yang_xian521/4398576
音频解码：http://download.csdn.net/detail/yang_xian521/4399219

音频编码：http://download.csdn.net/detail/yang_xian521/4399293

至此，我已经实现了视频的解码编码，音频的解码编码，相信有心人肯定可以在此基础上实现视频音频的同步压缩，不过要再看一些网上的资料，也是很轻松
的。至于视频的显示播放，大多数是要结合SDL实现，由于我只是浅尝辄止，只实现了图片的显示和简单的视频播放，比起我之前推荐的几个链接是弱爆了的，就
不写下去了，这个系列就到这里吧，希望能给像我一样的一些入门级选手点帮助。也欢迎大神来多多指教。

(附： 例子文件见360云盘的 所有文件-> work -> 音视频处理)